imalka marasinghe arachchilage
TRANSCRIPT
Synthesizing Laccol Based Polymers/Copolymers and Polyurethanes;
Characterization and Their Applications
by
Imalka Marasinghe Arachchilage
A dissertation submitted in the partial fulfillment
of the requirements for the degree of
Doctor of Philosophy
Department of Chemistry
College of Arts and Sciences
University of South Florida
Major Professor: Jianfeng Cai, Ph.D.
Julie P. Harmon, Ph.D. (late)
Randy Larsen, Ph.D.
Shengqian Ma, Ph.D.
Sylvia Thomas, Ph.D.
Date of Approval:
April 2nd
, 2021
Keywords: Lacquer, Cationic polymerization, Radiation hard, Ecofriendly
Copyright © 2021, Imalka Marasinghe Arachchilage
ACKNOWLEDGMENTS
Firstly, I would like to convey my sincere gratitude to late adviser Dr. Julie P. Harmon for her
guidance and help. Five and half years' time that I spent with her as my supervisor was
unforgettable and the things I learned from her is immense. Even though she couldn't make it to
see my last step in this PhD carrier, her unwavering consideration I received throughout my
journey is always remain in my heart as a precious memory. Secondly, I would like to convey
my sincere and heartfelt gratitude to Dr. Jianfeng Cai, who immediately received me and be my
advisor for the last semester due to the sudden departure of my previous supervisor. The support
and attention I received from him is unforgettable and it helped me to stand upright again during
the hard time. Further, I would like to convey my sincere gratitude to the committee members;
Dr. Shengqian Ma, Dr. Sylvia Thomas and Dr. Randy Larsen for their continuous guidance and
support throughout my journey.
I also would like to convey my sincere gratitude to Department of Chemistry and its affiliated
Academic & Administrative staff, Business & Fiscal staff and Laboratory staff at USF. Without
their support this success is difficult to achieve. Further, I would like thank all my past and
present lab colleagues; Dr. Ken Kull, Dr. Garrett Craft, Dr. Tamalia Julien, Dr. Alejandro Rivera
Nicholls, Taranjot Kaur and Nathaniel Johnson. Also, I would like to recognize all the
undergraduates that collaborated in the projects; Milly Patel, Joseph Basi and Mijeong Kim.
Finally, I would like to convey my sincere gratitude to my family; Rohini Marasinghe, Dilanka
Nadishani Ariyasena, Darshika Tharangani Ariyasena, Sanath Wickramasinghe, Savindu
Kankanige, Chandi Wijetunga, Ari Wijetunga, Sulochana Wijetunga and his family. Without
their support, this journey would not possible. Last but not least, I would like to thank my friends
I met in Florida and my friends in Sri Lanka, who help me throughout this long journey.
DEDICATION
I would like to dedicate this work to my dearest mother Rohini Marasinghe for her unwavering
support and also to my loving and wonderful 7 year old son Savindu Kankanige who is staying
with me all the time enduring lots of hardships.
i
TABLE OF CONTENTS
List of Tables ................................................................................................................................. iv
List of Figures ..................................................................................................................................v
List of Schemes ............................................................................................................................. vii
List of Equations .......................................................................................................................... viii
Abstract .......................................................................................................................................... ix
Chapter One: Introduction ...............................................................................................................1
1.1. Lacquer History ............................................................................................................1
1.2. Lacquer Tree .................................................................................................................2
1.2.1. Species and Distribution ................................................................................2
1.2.2. Lacquer Saps ..................................................................................................3
1.3. Cationic Polymerization................................................................................................4
1.3.1. Initiators used in Cationic Polymerization .....................................................5
1.4. Laccol based Polymers and Copolymers ......................................................................5
1.4.1. Laccol:Styrene Copolymers ...........................................................................6
1.4.2. Laccol:d-limonene Copolymers .....................................................................7
1.5. Radiation Hard Polymers/Copolymers and their Applications .....................................7
1.6. Polyurethanes ................................................................................................................8
1.6.1. Laccol based Polyurethanes ...........................................................................9
1.7. References ...................................................................................................................10
Chapter Two: Synthesizing radiation hard polymer and copolymers using laccol
monomers extracted from lacquer tree Toxicodendron succedanea via cationic
polymerization .........................................................................................................................13
Abstract ..............................................................................................................................13
2.1. Introduction .................................................................................................................14
2.2. Experimental Section ..................................................................................................17
2.2.1. Materials ......................................................................................................17
2.2.2. Preparation Procedures ................................................................................18
2.2.2.1. Extraction of laccol from lacquer sap ...........................................18
2.2.2.2. Synthesis of an Aluminum Chloride and Ethyl Acetate
[AlCl3.EtOAc] Complex ......................................................................18
2.2.2.3. Preparation of Laccol Polymer .....................................................18
2.2.2.4. Preparation of Polystyrene ............................................................20
2.2.2.5. Copolymers of laccol and Styrene ................................................20
ii
2.2.3. Characterization Methods ............................................................................22
2.2.3.1. Fourier Transform Infra-Red (FTIR) Analysis .............................22
2.2.3.2. Nuclear Magnetic Resonance Spectroscopy (NMR) ....................22
2.2.3.3. Gel Permeation Chromatography (GPC) ......................................22
2.2.3.4. Dynamic Mechanical Analysis .....................................................23
2.2.3.5. Thermal Gravimetric Analysis (TGA) ..........................................24
2.2.3.6. Shore Hardness .............................................................................24
2.2.3.7. Radiation Studies and Microscopic Analysis ...............................24
2.2.3.8. Wide Angle X-ray Scattering (WAXS) ........................................25
2.3. Results and Discussions ..............................................................................................25
2.3.1. FTIR Analysis ..............................................................................................25
2.3.2. NMR Analysis .............................................................................................29
2.3.3. GPC Analysis ...............................................................................................31
2.3.4. Dynamic Mechanical Analysis ....................................................................31
2.3.5. TGA Analysis ..............................................................................................34
2.3.6. Shore Hardness Analysis .............................................................................36
2.3.7. Microscopic Analysis...................................................................................37
2.3.8. Powder X-Ray Analysis ...............................................................................38
2.4. Conclusions .................................................................................................................39
2.5. Acknowledgment ........................................................................................................41
2.6. References ...................................................................................................................41
Chapter Three: Environmental friendly radiation hard d-limonene and laccol copolymers
synthesized via cationic copolymerization ..............................................................................45
Abstract ..............................................................................................................................45
3.1. Introduction .................................................................................................................46
3.2. Experimental Section ..................................................................................................51
3.2.1. Materials ......................................................................................................51
3.2.2. Preparation Procedures ................................................................................51
3.2.2.1. Copolymers of limonene and laccol .............................................51
3.2.3. Characterization Methods ............................................................................52
3.2.3.1. Fourier Transform Infra-Red (FTIR) Analysis .............................52
3.2.3.2. Nuclear Magnetic Resonance Spectroscopy (NMR) ....................52
3.2.3.3. Differential Scanning Colorimetry (DSC) ....................................53
3.2.3.4. Dynamic Mechanical Analysis .....................................................53
3.2.3.5. Thermal Gravimetric Analysis (TGA) ..........................................54
3.2.3.6. Shore Hardness .............................................................................54
3.2.3.7. Radiation Studies ..........................................................................54
3.2.3.8. Swelling Analysis .........................................................................55
3.3. Results and Discussions ..............................................................................................55
3.3.1. FTIR Analysis ..............................................................................................55
3.3.2. NMR Analysis .............................................................................................58
3.3.3. DSC Analysis ...............................................................................................61
3.3.4. Dynamic Mechanical Analysis ....................................................................62
3.3.5. TGA Analysis ..............................................................................................65
3.3.6. Shore Hardness Analysis .............................................................................67
iii
3.3.7. Swelling Analysis ........................................................................................68 3.4. Conclusions .................................................................................................................69
3.5. Acknowledgment ........................................................................................................71
3.6. References ...................................................................................................................71
Chapter Four: Synthesis and Characterization of Novel Laccol Based Polyurethanes .................76
Abstract ..............................................................................................................................76
4.1. Introduction .................................................................................................................77
4.2. Experimental Section ..................................................................................................82
4.2.1. Materials ......................................................................................................82
4.2.2. Preparation Procedures ................................................................................82
4.2.2.1. Synthesis of laccol and HMDI polyurethane (LH-1) ....................82
4.2.2.2. Synthesis of laccol and H12MDI polyurethane (LH-2) ................83
4.2.2.3. Synthesis of laccol and 4,4'–MDI polyurethane (LH-3) ...............83
4.2.3. Characterization Methods ............................................................................83
4.2.3.1. Fourier Transform Infra-Red (FTIR) Analysis .............................84
4.2.3.2. Nuclear Magnetic Resonance Spectroscopy (NMR) ....................84
4.2.3.3. Differential Scanning Colorimetry (DSC) ....................................84
4.2.3.4. Dynamic Mechanical Analysis .....................................................85
4.2.3.5. Thermal Gravimetric Analysis (TGA) ..........................................86
4.2.3.6. Micro Hardness .............................................................................86
4.2.3.7. Powder X-ray Analysis (PXRD) ...................................................86
4.2.3.8. Swelling Analysis .........................................................................86
4.3. Results and Discussions ..............................................................................................87
4.3.1. FTIR Analysis ..............................................................................................87
4.3.2. NMR Analysis .............................................................................................91
4.3.3. DSC Analysis ...............................................................................................93
4.3.4. Dynamic Mechanical Analysis ....................................................................94
4.3.5. TG Analysis .................................................................................................98
4.3.6. Micro hardness ...........................................................................................100
4.3.7. PXRD Analysis ..........................................................................................101
4.3.8. Swelling Analysis ......................................................................................102
4.4. Conclusions ..............................................................................................................102
4.5. Acknowledgements ...................................................................................................103
4.6. References .................................................................................................................103
Chapter Five: Conclusions ...........................................................................................................107
Appendices ...................................................................................................................................109
Appendix A: USF Fair Use Worksheet for Chapter One ................................................110
Appendix B: License of Reproduced Material in Chapter Two ......................................114
Appendix C: License of Reproduced Material in Chapter Three ....................................123
Appendix D: License of Reproduced Material in Chapter Four ......................................132
About the Author ............................................................................................................... End Page
iv
LIST OF TABLES
Table 2.1: Different monomer contents that used to prepare the copolymers ..............................20
Table 2.2: The MW of NLP and its copolymers at initial polymerization stage
(apolydispersity, PD = MW/Mn) ....................................................................................31
Table 2.3: Tg values and related activation energies obtained from rheometer ............................33
Table 2.4: Shore A hardness data for laccol polymer and copolymers;
before and after irradiation ...........................................................................................37
Table 3.1: Limonene and laccol contents in synthesized materials ..............................................52
Table 3.2: Glass transition temperatures and activation energies for synthesized
copolymers of limonene:laccol and neat laccol polymer (NLP) .................................63
Table 4.1: Tg values and corresponding ΔE values obtained from analysis .................................98
v
LIST OF FIGURES
Figure 1.1: Lacquer coated artifacts .................................................................................................1
Figure 1.2: World distribution of lacquer tree .................................................................................2
Figure 1.3: The structures of main components in different lacquer saps .......................................3
Figure 1.4: Laccol structure .............................................................................................................4
Figure 1.5: Separation of styrene and inhibitor (solvent extraction) ...............................................6
Figure 1.6: Synthesized novel PUs LH-1, LH-2 and LH-3 in film and disc form...........................9
Figure 2.1: IR spectra of (a) LE, NLP and (b) Styrene monomer ..................................................26
Figure 2.2: IR spectra of various laccol compositions; a) LE-control, a') LE-after
irradiation, b) NLP-control, b') NLP-after irradiation, c) S-90_control,
c') S-90_after irradiation, d) S-70_control, d') S-70_after irradiation,
e) S-50_control, e') S-50_after irradiation, f) NPS-control,
f') NPS-after irradiation, *NPS-Neat Polystyrene .......................................................28
Figure 2.3: NMR spectra for (a) LE and (b) NLP (*Acetone) .......................................................29
Figure 2.4: Laccol:Styrene (S-50) copolymer-control, (b) Laccol:Styrene (S-50)
copolymer-after irradiation ..........................................................................................30
Figure 2.5: (a) NLP-WLF behavior graph, (b) Master curve developed for NLP .........................33
Figure 2.6: Tan δ curves (c) for materials from temperature ramp experiment (rheometer) .........34
Figure 2.7: TG curves for NLP and S-90 samples .........................................................................35
Figure 2.8: Optical microscopy observations of polymers and copolymers
(Magnitude: 5x/0.12P) .................................................................................................38
Figure 2.9: Powder X-ray diffraction data for NLP and S-90 ........................................................39
Figure 3.1: IR spectrum of d-limonene with important functional groups .....................................56
vi
Figure 3.2: IR spectra of (a) d-limonene:laccol copolymers, (b) L-10
(10% limonene in laccol) before and after irradiation and (c) L-30
(30% limonene in laccol) before and after irradiation .................................................57
Figure 3.3: NMR spectra of (a) laccol extract and (b) L-30 copolymer, *Acetone .......................60
Figure 3.4: DSC curves for limonene:laccol copolymers ..............................................................61
Figure 3.5: Tan δ curves for limonene:laccol copolymers .............................................................64
Figure 3.6: WLF graphs for L-30 and L-50 ...................................................................................64
Figure 3.7: TG curves of L-10 and L-30; before and after gamma irradiation ..............................66
Figure 3.8: Shore A hardness data for synthesized copolymers; before and
after irradiation.............................................................................................................67
Figure 3.9: Percent weight gain of copolymers; before and after gamma irradiation ....................69
Figure 4.1: IR spectra of synthesized LH-1, LH-2 and LH-3 samples ...........................................88
Figure 4.2: IR spectra for; (a) Synthesized PUs before & after rheology (temp ramp)
experiment, (b) Synthesized PUs before & after molding ...........................................90
Figure 4.3: NMR spectra of LH-1, LH-2 and LH-3; *Acetone......................................................92
Figure 4.4: DSC data for LH-1, LH-2 and LH-3 at 30⁰C/min ramp rate .......................................94
Figure 4.5: Temp ramp experimental data for LH-2 and LH-3 to identify Tg ...............................95
Figure 4.6: LH-1 (a) WLF plot created from TTS for activation energy calculation
and (b) Master curve developed from WLF graph ......................................................96
Figure 4.7: TG curves for synthesized LH-1, LH-2 and LH-3 samples .........................................99
Figure 4.8: Micro hardness data for LH-1, LH-2 and LH-3 .........................................................100
Figure 4.9: PXRD data for synthesized PU samples (LH-1, LH-2, LH-3) ..................................101
vii
LIST OF SCHEMES
Scheme 2.1: Proposed mechanism for laccol polymerization ....................................................19
Scheme 2.2: Proposed mechanism for laccol and styrene copolymer formation .......................21
Scheme 3.1: Proposed mechanism for limonene:laccol copolymer formation ..........................50
Scheme 4.1: Generic mechanism for PU formation with diisocyanate ......................................81
viii
LIST OF EQUATIONS
Equation 1: Activation energy calculating equation .......................................................32,64,85
Equation 2: Percent weight gain calculating equation .........................................................55,87
ix
ABSTRACT
In modern world research scopes are highly favored the areas of developing new polymer
materials which are more integrated with the environment. Synthesizing eco-friendly, bio
degradable polymer materials to replace petroleum based synthetic polymers to utilize in
radiation hard applications is one of the main objectives of this study. 'Laccol' extracted from
Vietnamese lacquer tree (Toxicodendron succedanea) polymerized with other monomers namely
styrene and d-limonene (from citrus waste) respectively to develop copolymers via cationic
polymerization. Laccol contains hydroxyl phenyl groups that act as radical scavengers,
enhancing radiation resistance via their ability to convert excitation energy into non-chemistry
inducing energy in lacquer that has been cured. Further, laccol based polyurethanes were
synthesized which could possibly use as thermal insulator materials and as energy storing
materials is another objective investigated in this study. All these developments are novel and
reported firstly in the literature.
Lacquer saps are popular since ancient time periods because of its excellent toughness,
high solvent resistivity and high durability. It contains two reactive hydroxyl groups in the
phenyl ring and a C-17 unsaturated side chain at 3rd
position of the phenyl ring. Due to the
unsaturation of this C-17 side chain, it is a potent candidate for cationic polymerization process.
Firstly, the proper method was developed to homo-polymerize laccol through cationic
polymerization and procedure was further extended to produce copolymers of laccol:styrene and
x
laccol:d-limonene using AlCl3.EtOAc as the cationic co-initiator. Trans conjugated double bonds
in unsaturated side chain of laccol and terminal double bond in styrene or d-limonene was
involved prominently during the chain growth polymerization. Synthesized materials were
exposed to gamma radiation and alterations occurred due to irradiation process was studied.
Specifically the material hardness differences, FTIR information, crosslinking density
differences were investigated in addition to the other characterization techniques (DSC, TGA,
Rheology Analysis, NMR, GPC, XRD). Further, laccol based novel polyurethanes were
synthesized using three different diisocyanates groups (aliphatic; HMDI, cycloaliphatic;
H12MDI, aromatic; 4,4'-MDI) and characterized the materials using above mentioned techniques.
Deterioration of the materials after expose to gamma radiation is problematic in industrial
level operations (nuclear plants, medicinal sterilization plants) and space operations. Therefore,
development of new radiation hard materials is essential with improved properties such as
laccol:styrene copolymers we developed in this study. Though the petroleum based polymer
materials play a major role in these fields, it is high time to replace them with eco-friendly
materials such as d-limonene:laccol copolymers which possess promising radiation hard ability.
Generation of citrus waste in industrial scale at yearly basis is becoming a major environmental
concern nowadays. Therefore, development of radiation hard d-limonene:laccol copolymers
could possibly be a good solution to this environmental concern as well. The copolymers we
developed in this study are promising candidates to serve as radiation shield or protective
coatings in the high-tech industrial setup which are dealing with radiation such as nuclear
reactors, medicinal sterilization plants and outer space operations.
xi
The synthesized novel laccol based polyurethanes were characterized to identify their
properties. Mainly, the influence of different diisocyanates, hydrogen bonding capability and
crosslinking ability was investigated apart from other attributes. These analysis could provide
broader understanding to synthesized novel PUs in future developments. Prepared novel PUs
could possibly serve as thermal insulator materials in refrigerator coolant accessories, turbines
and incinerators. Also it can be useful as an energy storing material.
1
CHAPTER ONE: INTRODUCTION
1.1 Lacquer History
The 'oriental' lacquer has a long history and it was used as protective coating material which is
durable and cost effective since ancient times. Initially this was used as adhesive for repairing
chipped porcelain, fixing gold foil and attaching arrow heads to the wooden shafts. Later with
improved awareness this was further utilized in processing bamboo, wood and other objects.
Lacquer is still being utilized in day to day arts and crafts and as protective coatings for
industrial equipments [1]. Cultural artifacts which have a history of more than 2000 years still
preserved its beautiful appearance due to lacquer coatings. This is mainly because of its excellent
physico-chemical properties such as high solvent resistance, excellent toughness and high
durability [2-4]. Figure 1.1 illustrated some lacquer coated artifacts with high durability and
beautiful appearance.
Figure 1.1: Lacquer coated artifacts
(Images: https://en.wikipedia.org/wiki/Lacquer-Appendix A: USF Fair Use Worksheet)
2
1.2 Lacquer Tree
1.2.1 Species and Distribution
Lacquer is a natural product derived from lacquer tree belongs to genus Toxicodendron (formerly
Rhus), family of Anacardiaceae which has more than 73 genera and 600 species all over the
world [5]. This is considered as a mysterious natural coating material in human lives used for
more than thousands of years. Most of these lacquer trees grow in the subtropical regions in
Southeast Asia [5,6]. Even though there are lots of species of lacquer tree, only few lacquer trees
are able to produce lacquer sap. These are Toxicodendron vernicifluum which grows in China,
Japan, and Korea, Toxicodendron succedanea which grow in Vietnam and Taiwan, and Gluta
(former Melanorrhoea) usitata which grows in Myanmar, Cambodia, Lao, and Thailand [1,4,6].
Geographical distribution of these lacquer trees is illustrated in Figure 1.2.
Figure 1.2: World distribution of lacquer tree [1,6]
3
1.2.2 Lacquer Saps
The sap is collected after tapping the bark of the lacquer tree and usually tree age ranging from 5
to 15 years [1]. Different methods are utilized to tap the lacquer tree such as horizontal type, V
type, egg type and vertical/oblique type [6]. The main components of the saps collected from
Toxicodendron vernicifluum, Toxicodendron succedanea, Gluta usitata are urishiol, laccol and
thitsiol respectively as shown in Figure 1.3.
Figure 1.3: The structures of main components in different lacquer saps
In this study Vietnamese lacquer sap (Toxicodendron succedanea) was utilized to extract laccol
in acetone medium for material processing. Laccol contains two adjacent hydroxyl groups
attached to phenyl ring and in its 3rd
position has C-17 long side chain. This side chain contains
one to three unsaturations and therefore extracted laccol is a monomer mixture. In this mixture
~40% contains laccol monomer [6] which has three unsaturations in its side chain as illustrated
in Figure 1.4. This variant prominently involved in polymer and copolymer formation through
cationic polymerization process.
Urushiol Laccol Thitsiol
4
Figure 1.4: Laccol structure [1,6]
1.3 Cationic Polymerization
Cationic polymerization is feasible with the species that have unsaturation present in their
structures. Because of these double bonds it can readily form cations which later involves in
chain propagation. Cationic polymerization reactions are considerably faster compare to anionic
and radical polymerization reactions. The reason for this is formation of stable cation and its high
selectivity during the reaction [7]. Formed cation reacts with another electron donating group (in
this case a double bond) and propagation ensues. Initiation is required at the beginning of the
reaction and high performing cationic initiators are available for this purpose.
5
1.3.1 Initiators used in Cationic Polymerization
Protonic (Bronsted) acids or Lewis acids can be utilized to initiate the cationic polymerization
reaction. HBr, HI, H2SO4 are few examples for Bronsted acids and AlCl3, BF3, SnCl4 are few
examples for Lewis acids which can act as initiators in cationic polymerization process.
Aluminum chloride (AlCl3) is one of the highly effective cationic initiator in the polymerization
processes of styrene, isobutylene and other monomers [8]. AlCl3 is very strong Lewis acid which
can lead chain propagation, transfer and termination very rapidly. Also it has very poor solubility
in organic solvents [8]. In this study AlCl3 is reacted with ethyl acetate (EtOAc) to create
AlCl3.EtOAc initiator system [9,10] which is selective for the laccol based polymer and
copolymer formation in dichloromethane (CH2Cl2).
1.4 Laccol based Polymers and Copolymers
Laccol extracted from Vietnamese lacquer sap was homo polymerized with AlCl3.EtOAc as the
co-initiator. Residual water presence in the laccol initially activated the AlCl3.EtOAc complex
and later the hydroxyl groups present in laccol phenyl ring involve in the reaction to generate the
proton. This was reacted with double bonds presence in the laccol side chain as electrophilic
addition reaction to develop an active center for polymerization. Chain propagation occurred
through this way to produce laccol polymer and laccol based copolymers. These prepared
materials were characterized using different instruments FTIR (Fourier Transform Infra-red
Spectroscopy), NMR (Nuclear magnetic Resonance Spectroscopy), GPC (Gel Permeation
Chromatography), DSC (Differential Scanning Calorimetry), TGA (Thermal Gravimetry),
PXRD (Powder X-ray Diffraction), Shore A hardness, Microscopic analysis and Swelling
analysis as described in detail in Chapter 2 and 3.
6
1.4.1 Laccol:Styrene Copolymers
Styrene was copolymerized with laccol and terminal double bond present in styrene was reacted
with trans conjugated double bonds present in laccol side chain. Commercially available styrene
is usually inhibited with 4-tert-butyl catechol (TBC) to avoid unnecessary homo polymerization
of styrene [11]. Beginning of the experiment, TBC was removed by reacting with 15% (W/V)
sodium hydroxide (NaOH) using solvent extraction process in separatory funnel. Two layers
were formed inside the separatory funnel and bottom aqueous layer was removed while
collecting the pale yellow color upper layer as illustrated in Figure 1.5. This uninhibited yellow
color solution was dried using anhydrous magnesium sulfate (MgSO4) to remove residual water
[12]. Purified styrene was reacted with laccol in various ratios to develop different laccol:styrene
formulations. Synthesized materials were characterized to identify properties of each formulation
and their potent applicability as described in Chapter 2.
Figure 1.5: Separation of styrene and inhibitor (solvent extraction)
Uninhibited
styrene monomer
(upper layer)
Aqueous layer
(15% NaOH and
TBC)
7
1.4.2 Laccol:d-limonene Copolymers
Limonene is extracted from orange peels which accumulate in the environment as citrus waste.
Citrus is the most abundant crop in the world and only one third of it is processed as food [13].
Citrus plant belongs to the family Rutaceae and includes fruits such as oranges, lemon,
mandarin, lime, sour oranges and grape fruit [14]. Compare to total citrus production, ~80% is
oranges and 50% from whole fruit mass of oranges collected as citrus waste. When consider this
in industrial level, accumulation of citrus waste is a main environmental concern [13]. Therefore,
utilizing these citrus waste products to develop different chemicals is a thriving research area
recently. Extraction collected from orange peels contain both d and l limonene. Approximately
90% from the citrus peel oil contains d-limonene [15]. D-limonene is a monocyclic terpene with
two isoprene units and abundantly produced in nature as a secondary metabolite [16,17]. In this
study, d-limonene is reacted with laccol in different monomer ratios through cationic
polymerization to produce copolymers and characterized to identify their promising properties as
described in Chapter 3.
1.5 Radiation Hard Polymers/Copolymers and their Applications
Synthesized laccol:styrene copolymers and laccol:d-limonene copolymers were treated under
gamma radiation and alterations to the materials were studied comprehensively. Radiation
treatments were carried out using a gamma irradiator in University of Florida, Gainesville. A
1.25 MeV gamma ray source was delivered about 200-250 krad/hour (~30 Gy/min) to 6-8
adjacently placed samples for 336 hours. Many alterations occur to polymer materials due to
irradiation forming radicals, anions, cations and other different species. Polymer materials can be
8
cured further by exposing to radiation and this curing achieved through forming chemical and
physical crosslinks. Chemical crosslinks occur by forming new bonds between molecules and
physical crosslinks occur due to secondary interactions such as hydrogen bonding,
ionic/hydrophobic interactions and chain entanglements [18]. A three dimensional polymer
networks can be formed because of these crosslinks and this may influence the solubility of
materials. Lower solubility of polymer materials results due to high crosslink density and also
increases the material hardness accordingly. If the polymer material undergoes chain scission
due to irradiation it will increase the solubility and decrease the hardness [19]. The properties of
laccol based polymers/copolymers identified and experimented in this study; inevitably provide
better candidates to develop as protective coatings which can withstand high gamma radiation
environments such as nuclear reactors, space operations, commercial irradiators and medicinal
sterilization plants [20].
1.6 Polyurethanes
Polyurethane (PU) synthesis and processing has undergone immense differences since its first
discovery in 1930 by Otto Bayer and his coworkers in Germany [21]. Starting with polyurea
from aliphatic diisocyanate and diamine in 1930, it came a long way for today's achievements.
Several big industries such as DuPont, BASF, Dow Chemicals and Mobay contributed massively
for this development by improving their prominent R&D (research and development) sections
[21-23]. With these new developments, it is important to consider the effect to the environment.
Therefore, as a newly emerging research area PUs are synthesized utilizing vegetable oils to
avoid the harmful impact due to usage of chloro-alkenes as blowing agents [24,25]. With this
influence, an attempt was made in this study to develop novel laccol (extracted from Vietnamese
9
lacquer sap) based PUs using three different diisocyanates and materials were characterized to
identify their unique properties.
1.6.1 Laccol based Polyurethanes
Laccol extracted from Vietnamese lacquer sap consists two adjacent hydroxyl groups attached to
phenyl ring apart from the long side chain presence in 3rd
position of phenyl ring. Used
diisocyanates are aliphatic: 1,6-hexamethylene diisocyanate (HMDI), cycloaliphatic: 4,4’-
dicyclohexylmethane diisocyanate (H12MDI) and aromatic: 4,4’-diphenylmethane diisocyanate
(4,4'-MDI). These diisocyanates were reacted separately with laccol at presence of Tin(II) 2-
ethylhexanoate to produce three different PUs namely LH-1, LH-2, LH-3 respectively as
illustrated in Figure 1.6. Hydroxyl groups of laccol reacted with isocyanate groups and resultant
PUs were characterized accordingly as described in Chapter 4. In this study, main focus was
given to identify the influence of different diisocyanates in novel PUs, hydrogen bonding
capability and crosslinking ability which can provide broader characteristic scope for future
developments.
Figure 1.6: Synthesized novel PUs LH-1, LH-2 and LH-3 in film and disc form
Disc
Film Film Film
Disc Disc
10
1.7 References
1. Lu R.; Yoshida T.; Miyakoshi T.; Polymer Reviews, 2013, 53, 153–191, DOI: 10.1080/
15583724.2013.776585
2. Tsujimoto T., Ando N., Oy-Abu H., Uy-Ama H., Kobayashi S.; 2007, Journal of
Macromolecular Science, Part A: Pure and Applied Chemistry, 44, 1055–1060. DOI:
10.1080/10601320701424503
3. Yang J., Zhu J., Liu W., Deng J., Ding Y.; 2015, International Journal of Polymer
Science, 2015, Article ID 517202, 8 pages. DOI: https://doi.org/10.1155/2015/517202.
4. Yang J., Deng J., Zhu J., Liu W., Zhou M., Li D.; 2016, Progress in Organic Coatings,
94, 41–48. DOI: http://dx.doi.org/10.1016/j.porgcoat.2016.01.021
5. Honda T., Lu R., Sakai R., Ishimura T., Miyakoshi T.; 2008, Progress in Organic
Coatings, 61, 68–75. DOI: 10.1016/j.progcoat.2007.09.003
6. Lu R., Miyakoshi T.; Lacquer Chemistry and Applications; 1st Edition, Imprint: Elsevier,
Published on 25th August 2015, USA, 41–45. ISBN: 978-0-12-803589-4, DOI: http://
dx.doi.org/10.1016/B978-0-12-803589-4.00003-1
7. Galova M., Lux L.; 1975, Chem. zrest.i, 29 (3), 270 - 289
8. Kostjuk S. V., Dubovik A. Y., Vasilenkol I. V., Mardykin V. P., Gaponik L. V.,
Kaputsky F. N., Antipin L. M.; 2004, Polymer Bulletin, 52, 227–234. DOI: 10.1007/
~00289-004-0280-2
9. Vasilenko I. V., Frolov A. N., Kostjuk S. V.; 2010, Macromolecules, 43, 5503–5507.
DOI: 10.1021/ma1009275
10. Frolov A. N., Kostjuk S. V., Vasilenko I. V., Kaputsky F. N.; 2010, Journal of Polymer
Science: Part A: Polymer Chemistry, 48, 3736–3743; DOI: 10.1002/pola.24158
11
11. Kemmere M. F.; Mayer M. J. J.; Meuldijk J.; Drinkenburg A. A. H.; 1999, Journal of
Applied Polymer Science, 71, 2419–2422
12. Gellon A. A., Rietti V. M.; As May 26 1972, FR 2.109.780
13. Marın F. R., Soler-Rivas C., Benavente-Garcıa O., Castillo J., Perez-Alvarez J. A.; 2007,
Food Chemistry, 100, 736–741, DOI:10.1016/j.foodchem.2005.04.040
14. Rafiq S., Kaul R., Sofi S. A., Bashir N., Nazir F., Nayik G. A.; 2018, Journal of the Saudi
Society of Agricultural Sciences, 17, 351–358, DOI: http://dx.doi.org/10.1016/
j.jssas.2016.07.006
15. Byrne C. M.; Allen S. D.; Lobkovsky E. B.; Coates G. W.; 2004, J. AM. CHEM. SOC.,
126, 11404-11405, DOI: 10.1021/ja0472580
16. Ciriminna R., Lomeli-Rodriguez M., Cara P. D., Lopez-Sanchez J. A., Pagliaro M.; 2014,
Chem. Commun., 50, 15288–15296, DOI: 10.1039/c4cc06147k
17. Belgacem M. N., Gandini A., Editors; 2008, Monomers, Polymers and Composites from
Renewable Resources, 1st Edition, Elsevier Ltd. UK, Netherlands, 17–34, ISBN: 978-0-
08-045316-3
18. Maitra J., Shukla V. K.; 2014, American Journal of Polymer Science, 4(2), 25−31, DOI:
10.5923/j.ajps.20140402.01
19. Sun Y., Chmielewski A. G., Editors; 2017, Applications of Ionizing Radiation in Material
Processing; Institute of nuclear Chemistry and Technology, 1, Warszawa, 167−240,
ISBN: 978-83-933935-8-9
20. Holmes-Siedle A., Adams L. (Eds.); 2002, Handbook of radiation effects; United States:
Oxford University Press Inc., Second edition, 1−6. ISBN 0-19-850733-X
12
21. Sharmin E., Zafar F. (Editors); Polyurethane: An Introduction; Intechopen, London 2012,
pages 3–16, DOI: http://dx.doi.org/10.5772/51663, ISBN: 978-953-51-0726-2
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Journal of Macromolecular Science, Part B: Physics, 46, 853–875, DOI: 10.1080/
00222340701388805
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Reference Manual, Pittsburg 2005, pages 1–9
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25. Ourique P. A., Krindges I., Aguzzoli C., Figueroa C. A., Amalvy J., Wanke C. H.,
Bianchi O.; 2017; Progress in Organic Coatings, 108, 15–24, DOI: http://dx.doi.org/
10.1016/j.porgcoat.2017.04.002
13
CHAPTER TWO
SYNTHESIZING RADIATION HARD POLYMER AND COPOLYMERS USING
LACCOL MONOMERS EXTRACTED FROM LACQUER TREE TOXICODENDRON
SUCCEDANEA VIA CATIONIC POLYMERIZATION1
Imalka H. A. M. Arachchilagea, Milly. K. Patel
a, Julie P. Harmon
a,*
aDepartment of Chemistry, University of South Florida
*Corresponding author email: [email protected] (Prof. J. P. Harmon)
Abstract
In recent years lacquer chemistry stimulated more attention from the scientific
community due to its environmental friendly applications. Additionally, the 'laccol' possesses
promising radiation resistance due to its highly cross-linked polymer network. In nature, lacquer
polymerization is induced via enzymatic radical initiation. Herein, as a novel approach, lacquer
polymer was synthesized via cationic polymerization with aluminum chloride-ethyl acetate
(AlCl3.EtOAc) co-initiator. This approach was further improved by polymerizing copolymers of
laccol and styrene designed for use in radiation hard materials. The Infra-Red Spectroscopic data
clearly provide evidence for reactions with trans conjugated double bonds present in long side
chain (988 cm-1
and 966 cm-1
are bending vibrations of conjugated alkenes) of laccol monomer
accompanying the polymerization. This was further verified with proton Nuclear Magnetic
Resonance analysis. An increase in hardness was observed for all the compositions; remarkably
1 This chapter has been previously published in POLYM. ENG. SCI., 59:1611–1623, 2019, and has been reproduced
with permission from John Wiley and Sons Publishing (Appendix B). Second author Milly K. Patel (undergraduate
researcher at USF in 2018) involved in sample preparation and part of the analysis. Julie P. Harmon served as the
corresponding author for this publication.
14
for neat laccol polymer, 90% and 70% laccol-styrene copolymers after the gamma irradiation
using Co-60 gamma irradiator. Properties such as thermal stability and hardness were improved
after irradiation due to the increase of physical and small amounts of chemical crosslinking.
Therefore, the developed materials are suitable candidates to produce radiation hard polymer and
copolymer coatings for aerospace operations, nuclear reactors, medicinal and automobile sectors.
2.1 Introduction
For centuries 'oriental' lacquer has been used as coatings [1-3] and paints [1,4] in Asian
countries due to its high solvent resistant [1], excellent toughness [1] and high durability
[1,3,5,6]. Lacquer trees belong to the genus Toxicodendron (formerly Rhus) and family
Anacardiaceae with more than 73 genera and 600 species all over the world. Out of these
varieties only three kinds of lacquer trees are able to produce lacquer sap. The first variety is
Toxicodendron vericifluum, grows in the regions of China, Japan and Korea with the main
component of 'urushiol'. Secondly, Toxicodendron succedanea which grows in Vietnam and
Chinese Taiwan has 'laccol' as its main component. The third variety is Gluta usitata which
grows in Myanmar, Laos, Cambodia and Thailand having the 'thitsiol' as the main liquid
component [7]. In recent years, although many synthetic polymers and coatings have been
developed, lacquer sap is still attracting the attention because of its renewable ability, eco-
friendly nature and promising physico-chemical properties [3].
The Toxicodendron succedanea tree sap from Vietnam was utilized in this study to
synthesize polymer and copolymers. This lacquer sap has slow drying speed [7,8] compared to
urushiol, under 60-80% humidity environment via enzyme-catalyzed reaction [6]. The use of
filtered lacquer sap for the experiments and processing with laccase enzyme which was involved
15
in polymerization process is widely held in reported literature [1-6,8]. In contrast to this practice,
the 'laccol' (dark brown color liquid main component) extracted with acetone from the tree sap
was utilized for all the experiments conducted herein. It has C17 unsaturated hydrocarbon chain
with 0-3 olefins at the 3-position of the catechol ring [3,7,9] and 38.7% of the monomer mixture
contains 3 olefins in the side chain [7]. The laccase enzyme which is insoluble in acetone was
removed during the extraction process as 'acetone powder' [10]. The main constituent in laccol
mixture (acetone soluble components) which has 3 olefins in the side chain was significantly
involved in the cationic polymerization process incorporated herein.
Cationic polymerization is highly feasible with species containing double bonds and
reactions are considerably faster than the anionic and radical polymerizations [11]. According to
the predicted mechanisms in Scheme 2.1 and Scheme 2.2, water (H2O) interacts with co-initiator
(AlCl3.EtOAc) to generate the proton. Then, the electrophilic addition of proton to double bond
takes place to give the active center of the polymerization. This active center then initiates
polymerization and propagation ensues. Initiation of the cationic polymerization can be
achieved by using protonic acids (Bronsted) or Lewis acids [11]. A widely used Lewis acid
which is effective in cationic polymerization of styrene, isobutylene and other monomers is
Aluminum trichloride (AlCl3). This AlCl3 initiator is involved in rapid propagation reactions in
the systems including chain transfer and termination due to its strong Lewis acid nature.
However, AlCl3 has poor solubility in organic solvents [11,12]. To enhance the selectivity of
polymerization reaction, ethyl acetate (EtOAc) was introduced to AlCl3 for developing an
AlCl3.EtOAc complex [13,14]. This co-initiator complex was utilized herein to synthesize laccol
polymer and laccol-styrene copolymers. AlCl3.EtOAc was activated during the reaction by the
residual water in laccol mixture and carbocation was formed specifically in the conjugated
16
double bond region of the side chain of catechol ring. The two hydroxyl groups in the catechol
ring which are acidic and has able to form phenoxide anions to react with carbocation species in
the side chain. Additionally, formation of macrocyclic compounds is also possible due to
phenoxide anions and unsaturated groups (cis and trans double bonds) in side chain as discussed
by Rozentsvet et al [15]. These phenomena were investigated using IR and NMR data for laccol
polymer and laccol-styrene copolymers. The possible mechanisms for these processes are
illustrated in Scheme 2.1 and 2.2. The synthesized polymer and copolymers were exposed to
gamma radiation [16] and investigated the characteristic properties resulted from radiation
treatment.
The overall hypothesis behind this work is that the lacquer studied herein will exhibit
superior radiation resistance. This is substantiated by the fact that Toxicodendron succedanea
contains hydroxyl phenyl groups that act as radical scavengers, enhancing radiation resistance
via their ability to convert excitation energy into non-chemistry inducing energy in lacquer that
has been cured [17,18]. Further, Rogner and Langhals have shown via IR and Mass spectroscopy
that doses of 300 kGy (30 Mrad) electron beam (EB) do not result in measurable damage in qi-
lacquer (urushi) [19]. Additionally, Harmon’s group has shown that nanotubes enhance radiation
hardness of organic polymer matrices exposed to gamma rays [20-22].
Irradiated polymers could undergo various reactions forming cations, anions, gases and
other species. The two main types of reactions considered herein were crosslinking and chain
scission. The crosslinking can be physical, chemical or biological [23]. The chemical
crosslinking occurs between adjacent polymer molecules by forming new bonds and physical
crosslinks occur due to secondary interactions like hydrogen bonding, ionic interactions,
hydrophobic interactions and also due to entangle chains [24]. The biological crosslinking is also
17
a newly immerging area, however not yet developed in industrial level as chemical crosslinking
[23]. These processes could increase hardness of the polymer until it forms insoluble three-
dimensional network. Chain scission decreases the hardness and increases the solubility [25].
This makes them ideal candidates for use in radiation environments such as nuclear reactors,
machines for radiation therapy, industrial sterilization and space [26]. According to the literature,
radiation hardness of lacquer sap has not been investigated and references regarding lacquer sap
(urushiol and laccol) are limited to polymerization/curing studies primarily via UV and EB
radiation [4,6,19,27]. Therefore, in this paper the effort was made to synthesize radiation hard
laccol polymer and laccol-styrene copolymers using Toxicodendron succedanea lacquer sap
(from Vietnam) via cationic polymerization. The prepared materials were investigated in two
stages as cured control samples and irradiated samples by IR, NMR, GPC, Rheometer, TGA,
DSC, wide angle X-ray (WAXS) and shore A hardness methods.
2.2 Experimental Section
2.2.1 Materials
Raw lacquer sap was imported from Viet Lacquer Interior Co. Ltd in Vietnam. Reagent grade
acetone (CH3COCH3), dichloromethane (CH2Cl2) was used as solvents. Anhydrous Calcium
Chloride (CaCl2) granular, anhydrous Sodium Chloride (NaCl), anhydrous Magnesium Sulphate
(MgSO4), analytical grade sulphuric acid (H2SO4), hydrochloric acid (HCl), sodium hydroxide
(NaOH), 99.99% HPLC grade Tetrahydrofuran (THF) were obtained from Fischer Scientific.
Reagent Plus grade 99% Aluminum Chloride (AlCl3), 99.9% HPLC grade Ethyl Acetate
(EtOAc) and 99% Styrene monomer were purchased from Sigma Aldrich and inhibitor was
removed using 15% NaOH.
18
2.2.2 Preparation Procedures
2.2.2.1 Extraction of laccol from lacquer sap [5]:
A 100 g of filtered lacquer sap was mixed with 300.0 ml of acetone and stirred for 2 hours. The
mixture was vacuum filtered and the filtrate was collected. After much of the solvent acetone
was evaporated, two layer separations were observed due to the water content. The water layer
(bottom layer of the separatory funnel) was removed and the organic layer was further dried
using anhydrous CaCl2 granular. The vacuum evaporation was used to remove the excess
acetone. Up to 60-65% yield of laccol can be obtained from this extraction technique.
2.2.2.2 Synthesis of an Aluminum Chloride/Ethyl Acetate [AlCl3.EtOAc] Complex [13,14]:
EtOAc (2.3 ml, 2.25 x 10-2
mol) was added dropwise to slurry of AlCl3 (3 g, 2.25 x 10-2
mol) in
20.2 ml of dichloromethane (CH2Cl2) for 5 – 10 minutes. The reaction was allowed to stir for 30
– 60 minutes up to complete dissolving of AlCl3 to give a solution of complex (AlCl3.EtOAc) in
CH2Cl2 (~1 M).
2.2.2.3 Preparation of Laccol Polymer:
Polymerization reactions were carried out in erlenmeyer flasks inside an ice bath. As an example
of a typical procedure, polymerization was initiated by adding a solution of AlCl3.EtOAc in
CH2Cl2 (3.0 ml, ~1 M) to a mixture of laccol (10.0 g, ~6.07x10-2
mol) and CH2Cl2 (7.0 ml) while
stirring. After 15 minutes of stirring the sample had become more viscous and then it was
transferred to a polymer releasing paper which was folded to hold the sample. This was dried
under vacuum oven for 4 days at 60⁰C and partially cured samples were then dried under hot air
oven for 4 days at ~100⁰C. Proposed mechanism for the synthesis is illustrated in Scheme 2.1.
19
Scheme 2.1: Proposed mechanism for laccol polymerization
20
2.2.2.4 Preparation of Polystyrene:
Styrene monomer was purified by solvent extraction process with 15% (W/V) NaOH and dried
the organic layer using anhydrous magnesium sulphate (MgSO4) [28]. The polymerization was
initiated by adding AlCl3.EtOAc in CH2Cl2 (2.50 ml, ~1 M) to the mixture of Styrene (11.0 ml)
and CH2Cl2 (6.5 ml) while stirring in an ice bath under inert nitrogen atmosphere. The mixture
was stirred until it got more viscous and then it was kept under nitrogen atmosphere for
overnight. This was dried in vacuum oven for 4 days at 60⁰C.
2.2.2.5 Copolymers of laccol and Styrene:
The copolymers were prepared by mixing different monomer ratios of laccol and styrene as
illustrated in Table 2.1. S-10, S-15, S-30, S-50, S-70, S-90 sample names corresponded to 10%,
15%, 30%, 50%, 70% and 90% (w/v) laccol in styrene respectively. These samples were dried
under vacuum oven for 4 days at 60⁰C and partially cured samples were then dried under hot air
oven for 4 days at ~100⁰C.
Table 2.1: Different monomer contents that used to prepare the copolymers
Proposed mechanism for laccol-styrene copolymers formation is illustrated in Scheme 2.2.
21
Scheme 2.2: Proposed mechanism for laccol and styrene copolymer formation
22
2.2.3 Characterization Methods
Several methods were incorporated herein to identify the formation of polymer material and its
chemical, thermal and physical characteristics. Further, the effects resulted due to radiation
exposure was also investigated to identify the suitable polymer materials for applications.
2.2.3.1 Fourier Transform Infra-Red (FTIR) Analysis
For the FTIR study, a Perkin Elmer UATR Two spectrometer and solid samples were used
having the scan range of 400 – 4000 cm-1
set at a resolution 4 cm-1
and 16 average scans.
2.2.3.2 Nuclear Magnetic Resonance Spectroscopy (NMR)
NMR analysis was conducted on laccol polymer (LP) and its copolymers dissolved in
chloroform-d, using Varian INOVA 400 spectrometer. Instrumentation parameters were
employed as follows; Temperature maintained at 298K, spin set and maintained at 20Hz, 16
transients used in block sizes of 8, d1 relaxation time 2.000 second.
2.2.3.3 Gel Permeation Chromatography (GPC)
The molecular weight and molecular weight distribution of the laccol polymer and laccol-styrene
copolymers were determined by gel permeation chromatography (GPC) (PL-GPC 50 Integrated
GPC System, Polymer Laboratories). The partially cured samples were dissolved in THF to give
the concentration of 4 mg/ml and after 6 hours these samples were passed through 0.45 µm
filters separately. A 100 µl from each sample was injected at 30 ⁰C using THF as mobile phase
with a flow rate of 0.5 ml/min. A calibration curve was generated using monodispersed
23
polystyrene standards (Polymer Laboratories PS-2) to obtain the relative GPC data for the
samples.
2.2.3.4 Dynamic Mechanical Analysis [29]
Testing articles (rectangular bars with width 10.5 mm, length 50 mm and thickness 2 mm) were
molded in a heated Carver® hydraulic press with slow cooling to room temperature under
pressure. The isothermal strain sweep test was performed at -100⁰C to determine the linear
viscoelastic region (LVR) using AR 2000 (TA Instruments, USA) rheometer. Within the
measured LVR 0.3% strain was selected to characterize the samples with a temperature ramp in
oscillation mode to identify the glass transition temperature (Tg). Ramp conditions were -90ºC to
200ºC at 5 ºC/min for laccol polymer and copolymers, for synthesized polystyrene (PS) it was
0ºC to 200ºC at 10 ºC/min with liquid nitrogen for cooling. Further, frequency sweep experiment
was conducted using rectangular bars for laccol polymer and its copolymers, having the
frequency range from 0.1 – 10.0 Hz, 0.300% strain, starting temperature of -15⁰C with 5⁰C
increments each time until the sample collapse and for synthesized PS, strain was 0.200% and
starting temperature was 0ºC. Using the frequency sweep experimental data, activation energy
was calculated for each sample associated with glass transition temperature region.
Time sweep experiment was also performed for all the samples using parallel plate setup of the
rheometer with compression molded discs (diameter 1 inch and thickness 0.1 inch) having 2%
strain and 1.0 Hz frequency for 30 minutes at 150⁰C to observe the viscosity difference with time
at a specific temperature. Resulting data were analyzed with software available from TA
Instruments.
24
2.2.3.5 Thermal Gravimetric Analysis (TGA)
Thermal Gravimetric Analysis was performed on a TGA model TA Q50. A weight loss versus
temperature scans for different polymers and copolymers were recorded at a ramp rate of
10⁰C/min in air at the range between room temperature (~22⁰C) and 700⁰C.
2.2.3.6 Shore Hardness
ASTM D2240 Shore A was used to test the hardness of polymerized samples. Testing articles
(discs with diameter 1 inch and thickness 0.1 inch) were punched from sheets that were
compression molded using a Carver® laboratory press (model C) equipped with heating
elements. Hardness of the samples was measured before and after the γ-irradiation, before and
after rheometer experiments, before and after temperature treatment in dry oven at 200⁰C.
2.2.3.7 Radiation Studies and Microscopic Analysis
Co-60 Gamma Irradiator at University of Florida, Gainesville was used for the radiation studies.
A 1.25 MeV gamma rays source was utilized, delivering about 200-250 krad/hour (~30 Gy/min)
to 6-8 adjacently placed samples per each exposure. Samples were exposed to 9.8 Mega Rad in
air; this required 336 hours of exposure time.
Leica Microsystems Wetzlar GmbH instrument equipped with Leica DFC 290 camera (made in
Germany) was used to investigate the surfaces of prepared samples. Magnitude was set to PL
FLUOTAR 5x/0.12P and images were captured using Leica FireCam software.
25
2.2.3.8 Wide Angle X-ray Scattering (WAXS) [30]
To investigate the degree of crystallization of synthesized laccol polymer, laccol-styrene
copolymers and polystyrene, WAXS powder X-ray diffraction was used. X-ray diffraction
patterns were collected using Bruker D8 Focus x-ray diffractometer in the range of 2–70⁰ with a
step of 0.020⁰ at 25⁰C.
2.3 Results and Discussion
Cationic polymerization with AlCl3.EtOAc co-initiator successfully incorporated to develop
laccol polymer and laccol-styrene copolymers and this was confirmed from the results obtained
from IR, NMR, GPC and other characterization methods. These polymer and copolymers were
exposed to gamma radiation and reinvestigated the properties to identify the behavior of
materials after the radiation treatment. It was clearly indicated that NLP, S-90 and S-70
copolymers showed promising results towards the radiation hardening. Materials were further
cured and crosslinked (physically and/or chemically) due to the gamma radiation without
deteriorating and the obtained results were analyzed in detail here after.
2.3.1 FTIR Analysis
Identification of polymerizing process of lacquer based materials was frequently investigated
using FTIR data [1,4-8,23,31-33]. Figure 2.1(a) has the IR spectra of Laccol Extract (LE) and
Neat Laccol Polymer (NLP). It shows peaks at 3450 cm-1
due to hydroxyl groups (O–H), at 3010
cm-1
due to C–H stretching vibrations of unsaturated groups (cis and trans double bonds) in side
chain, at 2940 cm-1
due to methylene (C–H), at 1621 cm-1
, 1596 cm-1
and 1470 cm-1
due to
26
vibrations of phenyl ring (aromatic skeletal), at 988 cm-1
(trans) due to the bending vibrations of
conjugated alkene, at 966 cm-1
(trans) and 732 cm-1
(cis) due to alkenes in side chain [6,7,27].
Figure 2.1(b) is IR spectrum of purified styrene monomer which represents the peaks at 3010–
3083 cm-1
for C–H in aromatic group, at 1630 cm-1
for C=C, 907 and 990–1000 cm-1
for bending
vibrations of R–CH=CH2.
Figure 2.1: IR spectra of (a) LE, NLP and (b) Styrene monomer
27
The bending vibration for conjugated alkene at 988 cm-1
(trans) which is presented in the laccol
side chain was involved in the reaction via cationic polymerization process. The peak at 988 cm-1
completely disappeared after the polymerization process and the intensity of the peak at 966 cm-1
was reduced. This is possible due to the formation of laccol polymer and copolymers. This was
clearly identified with FTIR spectrum which was obtained for laccol polymer as illustrated in
Figure 2.1(a) as NLP. The peaks at 1278 cm-1
and 1184 cm-1
can be attributed as γO–H for laccol
and its copolymers. Comparing the curves LE and NLP in Figure 2.1(a), respective peaks for
γO–H significantly decreased in NLP, because of the formation of dimers and polymers [6]. This
scenario can be observed clearly from IR spectra c – e for the laccol and styrene copolymers as
well in Figure 2.2. The peak at 1352 cm-1
which is related to βO–H [6] also decreased in spectra
'b – e' compared to the curve 'a' in Figure 2.2. The peak at 3010 cm-1
which can be attributed as
the stretching vibration of the unsaturated group in the side chain was significantly reduced
possibly due to the crosslinking process occurred in the side chain. The peaks at 1621 cm-1
and
1596 cm-1
which are related to vibration of –C=C– bonds in phenyl ring were significantly
changed in Figure 2.1(a) NLP graph due to the formation of dimers and polymers. However, all
the synthesized materials are melt-processable.
Samples were reinvestigated after the irradiation process using FTIR and the peak at 966 cm-1
decreased as illustrated in Figure 2.2. The peak at 1690 cm-1
shifted to 1710 cm-1
and broadened
after the irradiation because of more laccol quinones formation [6]. The peaks at 1621 cm-1
and
1596 cm-1
were further changed after gamma irradiation due to the formation of dimers and
polymers [6]. The peaks in the region of 1350 – 1100 cm-1
also decreased in intensity after the
irradiation. These observations suggest that the laccol polymer and its copolymers were further
cured and have been crosslinked (physically and chemically) due to the gamma radiation without
28
deteriorating the material. Most promising results were observed for NLP, S-90, S-70 and S-50
samples.
Figure 2.2: IR spectra of various laccol compositions; a) LE-control, a') LE-after irradiation,
b) NLP-control, b') NLP-after irradiation, c) S-90_control, c') S-90_after irradiation,
d) S-70_control, d') S-70_after irradiation, e) S-50_control, e') S-50_after irradiation,
f) NPS-control, f') NPS-after irradiation, *NPS-Neat Polystyrene
29
2.3.2 NMR Analysis
Cationic polymerization of laccol polymer and its copolymers were further confirmed by 1H
NMR analysis. Completely cross-linked polymer and copolymers were insoluble in any organic
solvents or water, the partially dissolved samples of neat laccol polymer (NLP) and
laccol:styrene copolymers were investigated in this experiment. Laccol extract (LE) was
completely dissolved in CDCl3 and the obtained spectrum was compared to the NLP spectrum as
illustrated in Figure 2.3.
Figure 2.3: NMR spectra for (a) LE and (b) NLP (*Acetone)
The peaks relevant to the protons on the 13' to 16' carbon atoms were detected around 5.5–6.0
ppm completely disappeared after the laccol polymer formation. Also peaks relevant to cis
double bond at carbon number 10' and 11' reduced and new peaks appeared in the region of 4.0–
4.3 ppm (–C–O–C– bond formation) [2,8]. These new –C–O–C– bonds could form through the
30
side chain and also through the phenyl ring [6] due to the cationic polymerization (Scheme 2.1).
For the laccol and styrene copolymers; peaks relevant to cis double bond (10', 11') could
observed even after the polymerization process and peaks relevant to trans conjugated double
bonds (13' – 16') were completely utilized during the reaction. The –C–O–C– bond formation
was also observed as a minor product in the polymerized material (Scheme 2.2). Possibilities for
this observation are macrocyclic compound formation [15] and cross linking.
Reinvestigation of the samples was carried out after the irradiation process and it was confirmed
that the materials were further cured due to gamma radiation without deteriorating (Figure 2.4).
Peak at 4.0 ppm increased and it was evident for –C–O–C– bond formation [8] and possibility of
making macrocyclic compounds. Peaks relevant to cis double bond for copolymers were still
appearing after the gamma irradiation, but in less intensity.
Figure 2.4: Laccol:Styrene (S-50) copolymer-control, (b) Laccol:Styrene (S-50) copolymer-after
irradiation
One favorable possibility for this observation is inaccessible cis double bond due to random
orientation of molecules in the physically and chemically crosslinked three dimensional network.
31
Other possibilities are insufficient curing time or insufficient amount of styrene/laccol monomer
to allow the complete reaction.
2.3.3 GPC Analysis
Completely cured samples could not be dissolved in any solvent due to its high crosslinking
property and therefore, partially cured samples dissolved in THF were used for the experiment.
Molecular weight buildup was identified in each sample at the very beginning stage of
polymerization process. According to the results illustrated in Table 2.2, all the samples were
shown a molecular weight build up and it was significant for NLP and S-90 even in the very
beginning stage. This was again proved the successful incorporation of cationic initiator for the
polymerization.
Table 2.2: The MW
of NLP and its copolymers at initial polymerization stage
(apolydispersity, PD = M
W/M
n)
2.3.4 Dynamic Mechanical Analysis
The temperature region where the long chain segments slips is identified as the glass transition
temperature (Tg). The Tg was identified for samples using the tan δ curve from the temperature
32
ramp experiment for the rectangular shaped solid samples in rheometer. NLP showed the Tg
value of 15.40⁰C and for the copolymers, Tg values were decreased as S-30>S-50>S-90≈S-70.
According to the trend observed it was clear that the high styrene monomer consisting samples
showed the higher Tg value comparatively due to more ordered packing of the material. Also
with the increase of temperature a significant rubbery plateau was observed for S-30, S-50, S-70,
S-90 and NLP samples which are indicative of physical and/or small amounts of chemical
crosslinking (Figure 2.6).
The resulting graph (from frequency sweep data) created using Time-temperature superposition
software with shift factor versus temperature as shown in Figure 2.5(a,b) is an evidence of WLF
behavior and used to calculate the activation energy for each sample using the equation (1). C1,
C2 are material constants, R is universal gas constant (8.314 J.mol-1
.K-1
), T is temperature in
Kelvin (K) and Ea is activation energy [34,35]. Required energy to induce a large segment
slippage associated with glass transition was illustrated in Table 2.3. Highest activation energy
was observed for the S-90 sample and least was given by the S-70. NLP showed a 244.3 kJ mol-1
value in the glass transition temperature region.
∆𝐸𝑎 = (2.303) (𝐶1
𝐶2)𝑅𝑇2 (1)
The master curves were created using the above software and the storage modulus (G') always
predominant the loss modulus (G"). Figure 2.5(b) is an example for the master curve created for
NLP. Because of the high crosslinking property, completely cured samples were unable to test
using GPC to identify the molecular weights of final products as mentioned in section 2.3.3.
33
Table 2.3: Tg values and related activation energies obtained from rheometer
According to the data obtained from time sweep experiment, the viscosity increased with time at
150⁰C for all the samples and significant increment resulted from NLP, S-90 and S-70 samples.
This observation suggests a possibility of further curing of materials at a higher temperature as
reported in literature [3].
Figure 2.5: (a) NLP-WLF behavior graph, (b) Master curve developed for NLP
34
Figure 2.6: Tan δ curves (c) for materials from temperature ramp experiment (rheometer)
Tg of an amorphous polymer can be strongly influenced by molecular weight, tacticity, sample
weight, laboratory processing conditions and used ramp rate for the experiment [36-39]. The Tg
of synthesized polystyrene was identified using the temperature ramp experiment in rheometer.
The obtained experimental value was 102.8⁰C (Mw 20438) and this was inside the reported range
of Tg values from 96–106⁰C for polystyrene [37,40-43].
2.3.5 TGA Analysis
The change in sample mass is determined as a function of temperature or time in this technique.
Commonly used method is dynamic thermogravimetry where the sample is heated at a linear rate
in predetermined temperature changing environment [44]. Figure 2.7(a) illustrates the thermal
stability increment after addition of styrene. Figure 2.7(b) illustrates the results obtained for NLP
35
and S-90 samples after irradiation as a comparison to control samples. The degradation of neat
laccol polymer (NLP) could be described using two temperature stages [2,6].
Figure 2.7: TG curves for NLP and S-90 samples
36
The first stage of the NLP-control sample scan (50-150⁰C) with a weight loss of 3.63% was due
to the removal of residual water and other small molecules [2,6]. In the second stage (150-
500⁰C) with a weight loss of 83.4% can be attributed to degradation of laccol oligomer and
polymer. The irradiated NLP sample noted in the weight loss at the beginning of the scan and
after 150⁰C was less than the NLP-control sample, 2.87% and 76.6% respectively. Compared to
NLP, observed TG curves were similar for its copolymers. S-90 copolymer was chosen as an
example to demonstrate the data with NLP (laccol polymer). For S-90 control sample 2.02%
weight loss was observed in the first stage and in the second it was 80.0%. After the irradiation
process the weight loss after 200⁰C was reduced with the value of 77.4%. On set temperatures of
both irradiated NLP and S-90 samples were increased with the values of 384⁰C and 370⁰C
respectively compared to control samples. Additionally, a considerable amount of residue was
observed even after the 700⁰C for irradiated samples (NLP irradiated: 17.7%, S-90 irradiated:
17.4%) comparative to controls (NLP control: 11.8%, S-90 control: 16.5%). These observations
indicated that the irradiated samples possessed higher thermal stability possibly due to further
curing and crosslinking.
2.3.6 Shore Hardness Analysis
Shore A durometer was used for investigations due to the soft nature of synthesized materials.
Higher number of the scale from 0 – 100 indicates the greater resistance to indentation, and thus
harder materials [45]. According to the obtained results as shown in Table 2.4, addition of
styrene increased the hardness of the materials and irradiation further increased the physical and
chemical crosslinks, hence resulting harder materials. Higher laccol monomer containing
samples such as NLP, S-90, S-70 demonstrated significant increments of the hardness after
37
irradiation compared to initial readings. The effect of increased temperature during the
experimental steps and processing, to hardness property was also analyzed parallel to this study
and those data illustrated an increment of hardness for the NLP, S-90, S-70 and S-50 samples.
Table 2.4: Shore A hardness data for laccol polymer and copolymers; before and after
irradiation
2.3.7 Microscopic Analysis
The cured and processed discs were analyzed through optical microscope before and after the
gamma irradiation. Results were illustrated in Figure 2.8. It was clearly shown that more
wrinkles were appeared after the irradiation significantly for NLP, S-90, S-70 and S-50 samples.
This can be observed from the micrographs which illustrated more reflecting points than control
samples. The mechanism for the wrinkle formation and factors control the surface properties are
not clearly identified [4]. Curing process of the material could possibly lead to wrinkle formation
due to the evaporation of water and excess solvent. Exposure to gamma radiation could possibly
elicit more growing points for polymerization and remarkably increase the crosslinking density,
resulting in a hard cured material [4].
38
Figure 2.8: Optical microscopy observations of polymers and copolymers
(Magnitude: 5x/0.12P)
2.3.8 Powder X-Ray Analysis
A polymer is a macromolecule composed of many repeating sub units. The arrangement of these
sub units in a bulk polymer is controlled by molecular weight, chemical composition, spatial
orientation and processing conditions. Based on these factors polymers could show amorphous
or partially crystalline phase states. In crystalline state the arrangement of molecules are more
ordered and in the amorphous state it is more random. Amorphous polymers do not include long-
39
range order, thus consist with characteristically identifiable short-range order. As a result of this,
powder X-ray diffraction provides a diffuse peak signal [46]. According to the obtained results
as shown in Figure 2.9, controlled samples (NLP and S-90) have more crystallinity in the matrix
before exposing them to radiation. These diffused peaks are possible due to the local packing
arrangement of the molecules [47]. The distinct peak observed at 20⁰ repetitively for all the
compositions could possibly due to the main backbone chain of the polymer matrix (Scheme
2.1). After exposing the samples to gamma radiation, the peak observed at 20⁰ is preserved and
other peaks were diffused. The exact reason for the peak diffusion is not clearly identified and
possibilities could be different spatial orientation of the molecules, crosslinking, processing
conditions or chain scission.
Figure 2.9: Powder X-ray diffraction data for NLP and S-90
2.4 Conclusions
Laccol polymer and laccol-styrene copolymers were synthesized successfully incorporating
AlCl3.EtOAc cationic co-initiator. The unsaturated hydrocarbon chain in 3-position of laccol was
effectively cured with cationic co-initiator to produce physically and small amounts of
chemically crosslinked polymeric material. The changes occurred to IR peaks at 988 cm-1
, 966
40
cm-1
, 732 cm-1
(Figure 1 and 2) and the NMR peaks at 5.5–6.0 ppm range for NLP (Figure 2.3)
and copolymers after polymerization confirmed this statement. Flexibility of these amorphous
polymers was restricted below their Tg values [46]. Observed Tg values for polymer and
copolymers were ranging from 12.90⁰C to 29.60⁰C (Table 2.3). For synthesized polystyrene it
was 102.8⁰C. When the styrene monomer content increased in the copolymers, they became hard
and processability of the materials was increased, specifically for S-90, S-70, S-50, S-30
copolymers. Also, incorporating styrene to laccol monomer enhances the thermal stability of
copolymers. Exposure to gamma radiation enhances more growing points for polymerization and
significantly increases the crosslinking density which leads to increment of the hardness. The IR
and NMR data suggested the stable condition of materials after irradiation and evidences for
more physical and small amounts of chemical crosslinking. This was further justified by the data
obtained from temperature ramp experiment (tan δ curve) which illustrated a significant rubbery
plateau (Figure 2.6). The TGA and shore hardness data (Table 2.4) were evidenced the thermal
stability and hardness improvements of the materials. TG curves obtained for irradiated NLP and
S-90, clearly indicated higher onset temperatures and high residue weight even after 700⁰C.
NLP, S-90 and S-70 samples show significant hardness increments after the irradiation.
Microscopic observations also illustrated higher wrinkle formations after the irradiation process,
suggesting the fact of solvent evaporation and crosslinking. The wide angle X-ray data
exemplified significant differences due to gamma irradiation. As per the objective of the study,
synthesizing radiation hard polymer and copolymers was achieved and the prepared materials
were further cured through physical and chemical crosslinking without deteriorating after expose
to gamma radiation. Considering the factors like; processing ability, thermal stability and
radiation hard ability the neat laccol polymer (NLP) and S-90, S-70, S-50 copolymers are the
41
promising materials which illustrated the most profound outcome during this study. The
developed materials have a great potential for serving as protective layer or coating and radiation
shield against gamma radiation in the advanced high-energy radiation environments like nuclear
reactors, machines for radiation therapy, industrial sterilization and space [26].
2.5 Acknowledgement
Authors gratefully acknowledge Professor M. Luis Muga, University of Florida, Chemistry
Department, Gainesville, for performing gamma irradiation experiments and Professor Lukasz
Wojtas, University of South Florida, Chemistry Department for analyzing powder X-ray data.
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45
CHAPTER THREE
ENVIRONMENTAL FRIENDLY RADIATION HARD D-LIMONENE AND LACCOL
COPOLYMERS SYNTHESIZED VIA CATIONIC COPOLYMERIZATION2
Imalka H. A. M. Arachchilagea, Milly K. Patel
a, Joseph Basi
a, Julie P. Harmon
a,*
aDepartment of Chemistry, University of South Florida
*Corresponding author email: [email protected] (Prof. J. P. Harmon)
Abstract
In the modern world, petroleum based synthetic polymers have a great number of
applications in fields ranging from food packaging to space travel. However, the processing of
petroleum products and the resulting depletion of fossil fuels are major environmental concerns
in today’s society. As a result, the development of sustainable polymers which are made up of
renewable resources and waste products is an immerging area of research. Considering the world
food production, citrus fruit is most abundant and its contribution to waste generation is
immense. Therefore, this study focuses on offering an alternative to the use of petroleum based
polymers and also providing a regulatory pathway to manage citrus waste by developing novel
copolymers of laccol and limonene. Two environmental friendly compounds, laccol, derived
from the sap of Toxicodendron succedanea tree and limonene, extracted from orange peels, were
2 This chapter has been previously published in POLYM. ENG. SCI., 60:607–618, 2020, and has been reproduced
with permission from John Wiley and Sons Publishing (Appendix C). Second author Milly K. Patel (undergraduate
researcher at USF in 2018) involved in sample preparation and part of the analysis. Third author Joseph Basi
(undergraduate researcher at USF in 2019) involved in sample analysis. Julie P. Harmon served as the corresponding
author for this publication.
46
copolymerized via cationic polymerization to generate d-limonene:laccol copolymers with
radiation hardening capabilities which is relevant in fields such as nuclear energy generation,
medicinal sterilization, commercial irradiation and space exploration. Formation of these
copolymers was verified with Infra-Red and Nuclear Magnetic Resonance analysis. The
synthesized copolymers were characterized using different methods and exposed to Co-60
gamma radiation to identify alterations to their properties.
3.1 Introduction
Polymers play an essential role in modern society and currently the main source for the
components of synthetic polymers is fossil fuels. Monomers derived from petroleum products
can be used to synthesize polymers with extraordinary properties including remarkable
durability, conductive properties, and radiation resistance, all at a very low cost. However, the
environmental impact caused by depletion of these fossil fuels and the environmental damage
that accompanies processing petroleum products are rapidly becoming major issues with the use
of petroleum-based polymers. Therefore, in search of alternative measures, many scientists have
focused on producing environmental friendly and sustainable polymers from renewable sources
and waste products [1,2]. In particular, the incorporation of citrus waste into the next generation
of renewable polymers has recently gained considerable attention due to its appreciable
metabolites.
Out of the worldwide fruit and vegetable production, most abundant crop is Citrus and
one-third of the crop is processed [3]. In the entire industrialized crop, approximately 98%
contains oranges, lemons, grapefruits and mandarins which oranges are the most relevant with
47
82% of total. Citrus fruits are processed mainly to obtain juice. They are also used in the canning
industry to produce marmalade, segments of mandarin, and in chemical industry to extract
flavonoids and essential oils. From the whole fruit mass 50% of residual obtained as waste and it
consists of peels, seeds and fruit pulp remaining after juice and essential oil extraction [4]. When
considered on the industrial scale, this becomes a huge environmental concern. Therefore,
utilizing these waste products to develop useful chemical resources has recently become an
important topic of investigation. The citrus peel is a good source of a plethora of possibly useful
compounds, including molasses, pectin and limonene [5].
In this study, limonene extracted from citrus peels is utilized as one of two monomers
used to develop copolymers with laccol, a compound that is extracted from Vietnamese lacquer
sap. The major constituent of essential oil resulting from the citrus fruit skin is limonene and
90% of it contains d-limonene isomer [6]. This belongs to the family of terpenes [7]. Terpenes
are secondary metabolites synthesized mainly by plants, but also by a limited number of insects,
marine micro-organisms and fungi. Though these terpenes were initially considered as 'waste',
later their involvement in biosynthetic processes and ecological important role was discovered
[8]. Limonene is used in cosmetic production, foods and beverages as well as a green solvent
[2,7]. This contains double bonds which provide the necessary bifunctionality for polymerization
(Scheme 3.1-Limonene). Limonene is also an allylic monomer (CH2=CH-CH2R; R is the rest of
the molecule) which is hard to homo polymerize via free radical polymerization due to stable
radical formation and steric hindrance compared to vinyl radicals [9]. Therefore,
copolymerization of d-limonene using AlCl3.EtOAc cationic co-initiator with laccol monomer is
investigated herein as a novel approach.
48
Laccol monomer is extracted from Toxicodendron succedanea tree lacquer sap which
grows mainly in Vietnam. Lacquer saps are popular since ancient time periods because of its
excellent toughness, high solvent resistivity and high durability [10-13]. It contains two reactive
hydroxyl groups in the phenyl ring and a C-17 unsaturated side chain at 3rd
position of the phenyl
ring (Scheme 3.1-Laccol). Due to the unsaturation of this C-17 side chain, it is a potent candidate
for cationic polymerization process. As described in our previously published article [14], laccol
was successfully polymerized via cationic polymerization using AlCl3.EtOAc co-initiator.
Further broadening the applicability of laccol in industrial environment, copolymerization of
laccol with limonene via cationic polymerization was studied herein to develop radiation hard
copolymers. Copolymerization process involved two or more monomers during chain growth
polymerization which can balance the properties of commercial polymers [15]. Laccol and d-
limonene was copolymerized with AlCl3.EtOAc co-initiator. Conjugated double bonds (trans) in
unsaturated side chain of laccol and terminal double bond in limonene was involved prominently
during the chain growth polymerization. Additionally, as explained by Rozentsvet et al [16]
macrocyclic compound formation is also possible due to the phenate ions and cis/trans double
bonds (unsaturated groups) in the laccol side chain. These phenomenons were clearly observed
in the IR and NMR data obtained for the synthesized copolymers. During this cationic
polymerization process 70% of limonene by weight was able to copolymerize with laccol is a
promising outcome compared to the reported literature regarding limonene copolymers [17,18].
Synthesized copolymers irradiated with gamma rays and alterations to the properties of materials
were investigated.
The Overall hypothesis for this work is to develop environmental friendly sustainable
copolymers of limonene and laccol from citrus waste and lacquer sap via cationic polymerization
49
which possess potent radiation resistivity. These synthesized copolymers will be an alternative to
petroleum based synthetic polymers with appreciable properties and also a promising pathway to
regulate citrus waste. In laccol, there are hydroxyl groups which can behave as radical
scavengers. These hydroxyl groups can convert excitation energy into non-chemistry inducing
energy to enhance the radiation resistivity of lacquer [19,20]. In addition, enhancement of
radiation hardness in nanotubes of organic polymer matrices [21-23] and laccol polymer [14]
after gamma irradiation has shown by Harmon's group. Further, this is the first article
documenting the synthesis of laccol:limonene copolymers which possess radiation hardening.
Irradiation can cause many different alterations to the polymer matrix forming radicals,
anions, cations, gases and other different species. Curing of the polymer matrixes could be
achieved by the radiation exposure due to physical and chemical crosslinks formation. Physical
crosslinks can be formed because of secondary interactions such as ionic and/or hydrophobic
interactions, hydrogen bonding and chain entanglements [24] whereas chemical crosslinks occur
through two adjacent molecules forming a new bond. Formation of three dimensional networks
due to crosslinks could lower the solubility of polymer matrix and make the material harder.
Chain scissions also possible due to radiation exposure which make lesser hardened and
solubilize polymers [25]. These properties make the materials as ideal candidates to be used in
radiation hard environments in industrial setup such as nuclear reactors, medicinal sterilization
plants, commercial irradiators and space operations [26]. Limonene:laccol copolymers
synthesized herein was analyzed as cured copolymers and irradiated copolymers with the help of
IR, NMR, DSC, TGA, Shore Hardness and Swelling analysis.
50
Scheme 3.1: Proposed mechanism for limonene:laccol copolymer formation
51
3.2 Experimental Section
3.2.1 Materials
High purity food grade D-limonene was provided by Blubonic Industries and Viet Lacquer
Interior Co. Ltd in Vietnam provided the raw lacquer sap. Acetone (CH3COCH3) and
dichloromethane (CH2Cl2) were used as reagent grade solvents. Magnesium Sulphate anhydrous
(MgSO4), granulated anhydrous Calcium Chloride (CaCl2), HPLC grade (99.9%)
Tetrahydrofuran (THF) and sodium hydroxide (NaOH) were purchased from Fischer Scientific.
Aluminum Chloride (AlCl3) reagent plus grade 99%, Toluene (C7H8) assay 99.8% and HPLC
grade Ethyl Acetate (EtOAc) assay 99.9% were purchased from Sigma Aldrich.
3.2.2 Preparation Procedures
Laccol extraction, laccol polymer preparation and initiator preparation were carried out
according to the procedures published in our previous article [14]. High pure food grade d-
limonene was used as received without further purification.
3.2.2.1 Copolymers of limonene and laccol:
According to the monomer ratios illustrated in Table 3.1, copolymers of limonene and laccol
were synthesized. L-10, L-30, L-50, L-70 sample names corresponded to 10%, 30%, 50% and
70% (v/w) limonene in laccol respectively. Typical preparation procedure for L-10 copolymer is
as follows. A 36.0g of laccol extract was measured to a flask containing 3.70 mL of CH2Cl2.
While stirring the reaction mixture in an ice-bath, 4.70 mL of d-limonene was added and also
11.6 mL of initiator complex (~ 1M) was added dropwise afterwards. With time (15 – 30 min.)
52
the reaction mixture became more viscous. The vacuum oven was used to dry the samples for at
60⁰C for 4 days and another 4 days in hot air oven at ~100⁰C. Scheme 3.1 illustrated the
proposed mechanism for limonene-laccol copolymer formation [27,28].
Table 3.1: Limonene and laccol contents in synthesized materials
3.2.3 Characterization Methods
Identification of polymer formation and its thermal, physical and chemical characteristics were
studied using various characterization methods. Additionally, the effects resulted due to gamma
irradiation was also examined to identify the proper polymer matrices for applications.
3.2.3.1 Fourier Transform Infra-Red (FTIR) Analysis
Solid films prepared from polymer materials were used with UATR Two spectrometer (Perkin
Elmer) to conduct FTIR study. Parameters were maintained as follows; resolution set at 4 cm-1
,
400 – 4000 cm-1
scan range and 16 average scans for each experiment.
3.2.3.2 Nuclear Magnetic Resonance Spectroscopy (NMR)
Llimonene:laccol copolymers dissolved in chloroform-d was used for NMR analysis with Varian
INOVA 400 spectrometer having following instrument parameters. The temperatures was
Sample
Name
Laccol
Extract (g)
Limonene
(ml)
Initiator
Complex (ml)
CH2Cl2
Solvent (ml)
Total
Volume (ml)
L-10 36.0 4.70 11.60 3.70 20.0
L-30 28.0 14.20 10.80 5.00 30.0
L-50 20.0 24.00 10.00 6.00 40.0
L-70 12.0 33.30 9.20 7.50 50.0
53
maintained at 298K, spin set and maintained at 20Hz, 16 transients used in block sizes of 8 and
d1 relaxation time 2.000 second.
3.2.3.3 Differential Scanning Colorimetry (DSC)
The Differential Scanning Calorimeter from TA Instruments (model 2920) was used to identify
the glass transition temperature (Tg) of synthesized copolymers. Dry nitrogen gas with a flow
rate of 70 ml/min was purged through the sample cell. Cooling was accomplished with the liquid
nitrogen cooling accessory. For the temperature calibration Indium was used and three different
ramp rates were maintained (10⁰C/min, 20⁰C/min, 30⁰C/min) for proper identification of Tg
range. Samples were first cooled to -50⁰C, heated to +150⁰C, cooled again to -50⁰C and heated
again for second time to +150⁰C (two heating and cooling cycles).
3.2.3.4 Dynamic Mechanical Analysis
The rectangular bars were molded with length 50 mm, width 10.5 mm and thickness 2 mm using
heated Carver® hydraulic press with slow cooling to room temperature under pressure. The
linear viscoelastic region (LVR) was identified through isothermal strain sweep test at -100⁰C
using rheometer (TA Instruments, AR 2000, USA). The 0.3% strain was selected within the
measured LVR region to characterize the samples with a temperature ramp in oscillation mode to
identify the glass transition temperature (Tg). Conditions were maintained for temperature ramp
experiment as -60ºC to 200ºC at 10ºC/min for copolymers while cooling with liquid nitrogen.
In addition, rectangular bars were utilized to conduct frequency sweep experiment for
limonene:laccol copolymers. The parameters were adjusted for the experiment as follows;
54
0.300% strain, frequency range from 0.1 – 10.0 Hz, starting temperature of -15⁰C with 5⁰C
increments each time until the sample collapse. Activation energy associated in the glass
transition region was calculated for each sample using the frequency sweep experimental data.
3.2.3.5 Thermal Gravimetric Analysis (TGA)
A 10 mg sample of each copolymer formulations were analyzed using TA Q50 (TGA model).
Weight loss versus temperature scans were recorded at a ramp rate of 10⁰C/min in air from room
temperature (~22⁰C) to 700⁰C.
3.2.3.6 Shore Hardness
The hardness of polymerized samples was measured incorporating ASTM D2240 Shore A
durometer. Discs with diameter 2.54 cm and thickness 0.25 cm were punched from sheets that
were compression molded using a Carver® laboratory press (model C) equipped with heating
elements. Hardness of the samples was measured before and after the γ-radiation treatment
averaging eight indentations per sample.
3.2.3.7 Radiation Studies
The radiation studies were conducted using Co-60 Gamma Irradiator at University of Florida,
Gainesville. The utilized gamma ray source (1.25 MeV) was delivered about 200-250
krad/hour (~30 Gy/min) to 6-8 adjacently placed samples (discs with diameter 2.54 cm and
thickness 0.25 cm) per each exposure. Samples were exposed to 10.0 Mega Rad in air with the
required exposure time of 336 hours.
55
3.2.3.8 Swelling Analysis [29,30]
The sample flasks were prepared with ~30 ml toluene in each and limonene:laccol copolymer
specimens were placed at room temperature (~22⁰C) for 72 h. The exact weight (MI) of those
specimens was determined using a precision balance. After 72 h the solvent was decanted and
liquid solvent adhering to the sample's surface removed by short contact with filter paper. The
weight of the swollen polymer (MII) was determined immediately afterwards. Percent weight
gain was calculated as follows incorporating equation (1).
𝑊𝑒𝑖𝑔ℎ𝑡 𝑔𝑎𝑖𝑛 [%] = (𝑀𝐼𝐼
𝑀𝐼− 1) 100, 𝑀𝐼𝐼 ≥ 𝑀𝐼 (1)
3.3 Results and Discussion
Limonene and laccol copolymerized via cationic polymerization with AlCl3.EtOAc co-initiator
to produce environmental friendly sustainable copolymers which possess radiation hard ability.
Characterization of these copolymers were carried out using IR, NMR, DSC, Rheology, TGA
and various other methods. Samples were reinvestigated after the gamma radiation treatment to
identify the alterations occurred and L-10, L-30 samples illustrated the promising results. All the
samples were further cured due to crosslinks (physical and chemical) after gamma irradiation
and materials were not deteriorated. Obtained results analyzed with further details here after.
3.3.1 FTIR Analysis
Identification of important functional groups was acquired using FTIR for d-limonene and
resulted graph is illustrated in Figure 3.1. Peaks observed in the region of 3080–3020 cm-1
are for
56
stretching of unsaturated C–H group, 2925–2855 cm-1
for stretching of methylene group, 2970
and 2870 cm-1
for stretching of methyl, 1680 cm-1
for tri substituted double bond, 1646 cm-1
for
terminal methylene (–C=C–), 1438 and 1380 cm-1
for methyl and methylene bending, 888 cm-1
for out of plane bending of terminal methylene and 802 (840–800) cm-1
for out of plane bending
of tri substituted double bond [31].
Figure 3.1: IR spectrum of d-limonene with important functional groups
Peaks at 1644 cm-1
and 887 cm-1
which are relevant to terminal C=C bond were completely
utilized and peak at 802 cm-1
for out of plane bending of internal C=C bond was also involved in
the copolymerization process with laccol. A new peak at 1712 cm-1
was appeared which could
attribute as laccol quinones. In laccol monomer, peaks around 987 cm-1
and 968 cm-1
were
consumed during the reaction and this is a clear evident of polymerization which was occurred in
the side chain of laccol monomer. Obtained results were illustrated in Figure 3.2a. The peaks
related to phenyl ring vibrations were observed at 1621 cm-1
, 1596 cm-1
and 1470 cm-1
region.
57
Figure 3.2: IR spectra of (a) d-limonene:laccol copolymers, (b) L-10 (10% limonene in laccol)
before and after irradiation and (c) L-30 (30% limonene in laccol) before and after irradiation
58
The peaks at 988 cm-1
(trans) and 966 cm-1
(trans) were shown the bending vibrations of
conjugated alkene. Also cis alkene could observe in the region 732 cm-1
[13,32,33]. These
observed peaks were altered and/or completely disappeared during the copolymerization process.
According to the results maximum content of limonene in laccol was obtained as 70 weight
percentage (L-70 sample) and this is a promising outcome of the process compare to the reported
literature [17,18].
Samples were reinvestigated after the gamma radiation treatment. The peaks relevant to phenyl
ring –C=C– vibrations (1621 cm-1
, 1596 cm-1
and 1470 cm-1
) were mainly altered after the
gamma radiation treatment as illustrated in Figure 3.2(b and c) due to the formation of dimers
and polymers [13,33]. The peak at 1640 cm-1
shifted to 1710 cm-1
and broadened after gamma
irradiation due to the formation of laccol quinones [13,33].
Peaks at 987 cm-1
and 968 cm-1
were reappeared after radiation treatment. Because of the gamma
radiation feasibility of forming radicals is increased and it could favor the reactions occurring
through phenyl ring of laccol with limonene terminal double bond [13,33] compared to laccol
side chain reactions. According to the obtained results all the samples were cured further because
of radiation. Also physical and small amount of chemical crosslinks involved in the curing
process. Materials were not deteriorated after expose to gamma radiation and promising results
were observed for L-10 and L-30 copolymers.
3.3.2 NMR Analysis
Copolymer formation between d-limonene and laccol via cationic polymerization was further
confirmed using 1H NMR analysis. Cured polymers were hard to dissolve in any organic solvent,
59
therefore partially solubilize samples in deuterated chloroform were analyzed herein. The NMR
spectrum of laccol extract (Figure 3.3a) was used to identify the involvement of functional
groups in the reaction with d-limonene. Peaks appeared in the region of 5.5 to 6.0 ppm denote
the conjugated double bonds (13' – 16') in the laccol side chain. In the region of 5.0 to 5.5 ppm
denotes the cis double bond (10', 11') of the side chain and hydroxyl groups (a) in the phenyl
ring. For d-limonene peaks in the region 4.5 ppm denotes the terminal C=C bond and region 5.0
to 5.5 ppm denotes the internal C=C bond [34].
During the copolymerization process the peaks at 4.1 to 5.0 ppm region (Figure 3.3b) which
represent the terminal C=C bond of d-limonene [34] and peaks at 5.5 – 6.0 ppm region which are
relevant to conjugated double bonds in laccol side chain [35,36] were disappeared. This provides
the clear evidence of cationic polymerization which occurred through these double bonds of
limonene and laccol. Further the peaks relevant to laccol phenyl ring 4–6 were reduced and this
could be due the crosslinking reactions occurred through phenyl ring. New peak appears in the
region 4.0 to 4.3 ppm which is related to –C–O–C– bond formation during the process. The
formation of new –C–O–C– bonds could observe through phenyl ring and also through the side
chain [13] because of the cationic polymerization as illustrated in Scheme 3.1. Further this could
be due to the macrocyclic compound formation [16] as well during the copolymerization of d-
limonene and laccol. After the gamma irradiation; test samples became harder and it was
difficult to dissolve in any solvent to do the NMR analysis for data collection after radiation
treatment.
60
Figure 3.3: NMR spectra of (a) laccol extract and (b) L-30 copolymer, *Acetone
61
3.3.3 DSC Analysis
Glass transition temperature (Tg) of the materials was analyzed using the differential scanning
calorimetry. Tg value is greatly influenced by the tacticity, molecular weight, sample weight,
ramp rate and laboratory processing conditions [37-40]. To identify the proper Tg region three
different ramp rates (10⁰C/min, 20⁰C/min and 30⁰C/min) were used in the analysis and results
obtained for 30⁰C/min ramp rate was illustrated in Figure 3.4. With increment of the ramp rate,
the Tg values are also increased accordingly for each synthesized copolymer (Table 3.2). Neat
laccol polymer (NLP) and d-limonene were used as control samples during the experiment.
Figure 3.4: DSC curves for limonene:laccol copolymers
Data obtained for NLP is broad and rheology is a proper method to analyze Tg for NLP [14]. D-
limonene homo polymer was very brittle and could not use to develop rectangular bars for
62
rheology analysis. Therefore, DSC was utilized to analyze Tg and obtained value was 72.5 ⁰C at
30⁰C/min ramp rate (Table 3.2). L-10, L-30 and L-70 samples were illustrated significant change
in the heat flow inside the temperature region of 5⁰C to 55⁰C which is a broad Tg range. To
further confirm the Tg values of each copolymer and their activation energies; rheology was used
and results were analyzed in detail at section 3.3.4.
3.3.4 Dynamic Mechanical Analysis
Rheometer was utilized for this analysis to identify the glass transition temperature (Tg) where
long chain segments slip at specific temperature region. Tan δ curve obtained from the
experiment of temperature ramp was used to identify the Tg values for each limonene:laccol
copolymer as illustrated in Table 3.2. Tg values obtained for copolymers were reside in the
temperature region of 17.0⁰C to 24.0⁰C with the increasing order of L-30<L-10<L-70<L-50.
According to the results more ordered packing was observed for L-50 with higher Tg value. This
copolymer contains 1:1 monomer ratio from both laccol and limonene. When deviating from the
1:1 monomer ratio, it could possibly effects the physical crosslinking of the materials hence
disturbs the proper packing of the molecules in temporary network.
The observed plateau in the rubbery region specifically for L-10, L-50 and L-70 tan δ curves as
shown in Figure 3.5 was a consequence of long molecules entanglement which led to physical
crosslinks that restrict molecular flow through the formation of temporary networks [41]. At
higher temperatures tan δ curve shows increment, possibly due to the reactions occurring inside
the materials which influenced further curing [11].
63
Table 3.2: Glass transition temperatures and activation energies for synthesized copolymers of
limonene:laccol and neat laccol polymer (NLP)
Sample Name
Tg (⁰C) values at different ramp rate
From DSC analysis From Rheometer
10⁰C/min 20⁰C/min 30⁰C/min Tg (tan δ
curve)
Activation
Energy (kJ)
L-10 14.1 18.1 25.6 20.5 243
L-30 12.6 17.9 20.3 17.1 242
L-50 13.0 34.4 35.4 23.4 258
L-70 14.1 33.0 41.2 21.8 245
NLP 14.6 36.7 45.6 15.4 244
After the gamma irradiation the test samples could not use for DMA analysis due to the fact of
the sample shapes. For the radiation studies disc shaped was utilized per the requirement and for
DMA, rectangular bar shaped was required for better analysis of Tg and activation energy. If the
samples were remolded after the gamma radiation studies, it could cause a different effect due to
temperature increment and this will alter the data. Therefore, alternative test methods were
utilized to support the crosslinking process after gamma radiation as described in sections 3.3.1,
3.3.5, 3.3.6 and 3.3.7.
Frequency sweep experiment was conducted to calculate the activation energy in the region of
glass transition temperature (Table 3.2). Resulting graphs from this experiment were analyzed
via Time-temperature superposition software with shift factor versus temperature and obtained
results were followed WLF behavior. Accordingly activation energies were calculated using the
equation (2) where R is universal gas constant (8.314 J.mol-1
.K-1
), C1, C2 are material constants,
T is temperature given in Kelvin (K) and Ea is the activation energy [42,43]. L-50 sample was
shown the highest activation energy and the least was observed for L-30 sample. For the L-50
sample higher Tg was observed hence more ordered packing and therefore required high
64
activation energy to move long chain segments in the glass transition region. As the control
sample, NLP was shown 244 kJ mol-1
value as the activation energy in the Tg region. Obtained
WLF graphs for L-30 and L-50 were illustrated in Figure 3.6.
∆𝐸𝑎 = (2.303) (𝐶1
𝐶2) 𝑅𝑇2 (2)
Figure 3.5: Tan δ curves for limonene:laccol copolymers
Figure 3.6: WLF graphs for L-30 and L-50
65
3.3.5 TGA Analysis
Weight loss of the materials was identified incorporating dynamic thermogravimeric method
where the sample is heated at a linear rate in predetermined temperature changing environment
[44]. Promising results were obtained for L-10 and L-30 copolymers which were used as
examples to describe the results herein. Figure 3.7 illustrates the TG curves of L-10 and L-30,
before and after the gamma radiation treatment. In the temperature region from 50.00⁰C to
200.0⁰C the weight loss of copolymers L-10 and L-30 was less than 2.000% for both control and
irradiated samples. This is possible due to the removal of small molecules and residual water
[13,35]. From 200.0⁰C to 450.0⁰C temperature region L-10 control sample weight loss
percentage was 61.18% and L-30 was 65.83%. This is possible due to the copolymer
degradation. After the gamma irradiation treatment the weight loss percentages were reduced for
L-10 and L-30 samples with the values of 54.69% and 64.21% respectively. Onset temperatures
for L-10 copolymer before and after irradiation were 389.1⁰C and 380.0⁰C. For L-30 copolymer
onset temperature was increased after the gamma radiation significantly with 14.72⁰C. Before
the radiation treatment the value was 379.0⁰C and after the radiation treatment it was 393.7⁰C.
These observations provide clear evidences for further curing of copolymers due to the gamma
radiation. In addition these copolymers illustrated high thermal stability after radiation treatment
leaving significant amount of residuals. After 600.0⁰C for L-10 control sample has 24.26%
residual and irradiated sample has 26.81% residual. For L-30 sample this was 18.35% (control)
and 19.12% (irradiated sample) after 650.0⁰C. These results further supporting the statement of
curing through crosslinking due to gamma radiation.
66
Figure 3.7: TG curves of L-10 and L-30; before and after gamma irradiation
67
3.3.6 Shore Hardness Analysis
Hardness of the copolymers was measured using Shore A durometer due to the soft nature of the
materials. Scale is driven through 0 – 100 in the durometer and higher numbers depicted greater
resistance to indentation; hence harder materials [45]. The hardness was increased for all the
limonene:laccol copolymers after the gamma irradiation due to further curing through
crosslinking (physical and chemical) compared to control samples according to the results
illustrated in Figure 3.8.
Figure 3.8: Shore A hardness data for synthesized copolymers; before and after irradiation
Increment of the hardness was observed for L-30, L-50 and specifically for L-70 sample which
has 70% of limonene on its weight. This is possibly due to the reactions occurring with the
radiation. Gamma radiation could induce radical formation and other reactions inside the
68
materials which could increase the ability of copolymers to undergo more crosslinking other than
the cationic polymerization. When the amount of limonene is increased these side reactions were
more feasible because of the smaller size of the limonene molecule. Smaller the size, there is a
higher possibility to penetrate the 3D polymer network by limonene to react with laccol phenyl
ring due to radiation treatment according to the results shown in Figure 3.8. Elevated
temperatures also increase the hardness of copolymers.
3.3.7 Swelling Analysis
The swelling properties depend on many factors such as polymer network density, nature of the
solvent and polymer-solvent interactions [46]. Swelling analysis was conducted in toluene
solvent to identify the crosslinking nature of the synthesized limonene:laccol copolymers
[29,30]. Percent weight gain of copolymers was calculated before and after gamma radiation
treatment as illustrated in Figure 3.9. For control samples the percent weight gain remained
mostly in the same range since the only difference in the materials were monomer mixing ratios.
When the crosslinking density increases, free volume inside the polymer network is decreased;
hence percent weight gain is reduced accordingly [47]. According to the obtained results L-10,
L-30 and L-70 copolymers were shown a significant reduction of percent weight gain after
gamma irradiation. This provides a clear evidence of more physical and chemical crosslinks
formation during the radiation treatment. With radiation radical formation is increased and this
could provide more freedom to form crosslinks inside the polymer network which ultimately led
to lesser free volume for solvent uptake. Obtained results depicted this phenomenon for all the
synthesized copolymers after gamma radiation treatment.
69
Figure 3.9: Percent weight gain of copolymers; before and after gamma irradiation
3.4 Conclusions
Synthesizing environmental friendly sustainable limonene and laccol copolymers via cationic
polymerization [48,49] was successfully achieved using AlCl3.EtOAc co-initiator.
Copolymerization was occurred through mainly trans conjugated double bonds in the laccol
monomer side chain and terminal double bond of the limonene. Internal double bond of the
limonene also involved in the reaction for lesser extent compare to major reaction as illustrated
in Scheme 3.1. Alterations occurred to the peaks 1644, 887 cm-1
which are relevant to terminal
C=C bond of limonene, 802 cm-1
for internal C=C bond of limonene, 987 cm-1
, 968 cm-1
vibrations of trans conjugated double bonds in the IR spectra (Figure 3.2) provide evidence for
the successful copolymerization process. NMR data further confirms this fact as shown in Figure
3.3. Limonene was able to copolymerize with laccol up to 70% weight out of total weight is
70
another promising outcome of this study. Glass transition temperatures and their corresponding
activation energies of the Tg region were identified for processing purposes of the materials. IR
data collected after gamma radiation was shown a new peak at 1712 cm-1
for laccol quinones
formation and similar signal pattern with some alterations compare to controls, stating the fact
that the samples were not deteriorated. Thermal stability of L-10 and L-30 copolymers was
increased after gamma irradiation comparative to controls. Significant amount of residual was
observed for L-30 specifically even after the 650.0⁰C. This is a clear evidence of further curing
through physical and chemical crosslinks due to radiation. Similarly shore A hardness was also
increased for all the copolymers after gamma radiation, supporting the fact mentioned
previously. Further, swelling analysis provided the clear evidence of crosslinks increment due to
gamma irradiation by decreasing the percent weight gain. Gamma radiation could produce
radicals which possibly induce more growing points of the polymer network ultimately led to
increase of crosslink density. As per the objective of the project synthesizing environmental
friendly sustainable limonene:laccol copolymers which possess compelling radiation hardening
was achieved. The significance of this study is the development of novel limonene:laccol
copolymers as an alternative to petroleum based synthetic polymers in radiation hard
applications and also provide a reliable solution to citrus waste problem. L-10, L-30 and L-70
samples are the most promising candidates to serve as radiation shield or protective coatings in
the high-tech industrial setup which are dealing with radiation such as nuclear reactors,
medicinal sterilization plants and outer space operations [26].
71
3.5 Acknowledgement
The gamma irradiation experiments were performed by the Professor M. Luis Muga, Chemistry
Department, University of Florida, Gainesville. Authors gratefully acknowledge Professor Muga
for the support provided towards the success of this study.
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CHAPTER FOUR
SYNTHESIS AND CHARACTERIZATION OF NOVEL LACCOL BASED
POLYURETHANES3
Imalka H. A. M. Arachchilagea, Joseph Basi
a, Shahedul Islam
a, Julie P. Harmon
a,*
aDepartment of Chemistry, University of South Florida
*Corresponding author email: [email protected] (Prof. J. P. Harmon)
Abstract
Development of polyurethanes (PU) has come a long way from their origin in 1937 and have
unique applications in a diverse set of fields. Recent PU developments are focusing more on the
naturally derived diols in the synthesis process in an effort to make them more environmentally
friendly. In this study three different diisocyanates (aliphatic, cycloaliphatic and aromatic
diisocyanates) were combined with laccol which extracted from Vietnamese lacquer sap
(Toxicodendron succedanea) to synthesize novel PUs. Influence of the different diisocyanates in
novel PUs, hydrogen bonding capability and crosslinking ability were investigated to provide a
broader characteristic scope for future developments. Resulting materials illustrated good
thermal stability after exposed to higher temperatures and the hydrogen bonding regions
corresponding to N–H (3326 cm-1
) and C=O (1652 cm-1
) groups were shifted to higher
3 This chapter has been previously published in Polym Eng Sci. 2020;1–13. https://doi.org/10.1002/pen.25608, and
has been reproduced with permission from John Wiley and Sons Publishing (Appendix D). Second author Joseph
Basi (undergraduate researcher at USF in 2019) involved in sample preparation and analysis. Third author Shahedul
Islam helped with NMR analysis. Julie P. Harmon served as the corresponding author for this publication.
77
wavenumber according to FT-IR (Fourier Transform Infra-red Spectroscopy) analysis. Further
curing occurred with temperature treatment and improved the overall quality of novel PUs.
Powder X-ray (PXRD) analysis, micro hardness and swelling analysis were utilized to identify
molecular packing and crosslinking effects. Higher crosslink density observed for cycloaliphatic
and aromatic diisocyanate incorporated novel polyurethanes compared to aliphatic diisocyanate
incorporated polyurethane.
Keywords: Polyurethanes, FT-IR, Crosslinking, Hardness, Swelling
4.1 Introduction
Over the years from late 1930 to date, polyurethane (PU) synthesis has developed in
numerous ways with improved properties and material qualities. First discovery of PU was in
1937 by Otto Bayer and his coworkers in Germany forming polyurea from aliphatic diisocyanate
and diamine [1]. In 1952 polyisocyanate became commercially available which lead to vast
development of different polyester-polyisocyanate systems developed by Bayer group. Over time
polyester-polyols were gradually replaced by polyether-polyols due to its advantages; qualities
such as low cost and, ease of handling and improved hydrolytic stability [1,2]. DuPont, BASF
and Dow Chemicals also involved actively in the development process of new PUs. During the
past few decades PU has developed in numerous ways from flexible PU foams to rigid PU
foams. Since 1955, Mobay Cooperation has also presented a variety of monomeric and
polymeric isocyanates, polyethers, polyesters and acrylics to utilize in formulation of PUs [3].
Considering the environmental effect due to chloro-alkenes as blowing agents, development of
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PUs utilizing vegetable oils immerged as a new research area [4,5]. Currently researchers are
allotting significant amount of time, energy and resources to develop environmental friendly,
quality PU designs for applications. Therefore in this study we focused on developing and
characterizing laccol (extracted from Vietnamese lacquer sap) based PUs with different
diisocyanates which can be improved further for different applications.
Urethane linkages are formed through the reaction between alcohol and isocyanate. The
reaction between di-functional alcohol and di-functional isocyanate leads to the formation of PU.
To design PUs with superior qualities such as resistance to abrasion, chemicals, and higher
temperatures, it is necessary to have multiple functional groups in the reacting partners which
can lead to the development of three dimensional crosslinked networks [3]. Hydroxyl groups
containing substances are usually called as polyols and it is one of the major reactants in PU
synthesis. Depending on the molecular weights of polyols, rigidity of the PUs is differentiated.
Rigid PUs are produced from lower molecular weight polyols and high molecular weight long
chain polyols are utilized to synthesize flexible PUs [1]. In this work laccol extracted from
Toxicodendron succedanea (Vietnamese lacquer sap) was utilized as the source of diol which
consists of a C-17 long side chain at its 3rd
position of the ring (Scheme 4.1-Laccol). Because of
the unsaturation present in the side chain, laccol extract usually appeared as a mixture. Most
abundant component (~40%) of the extract is 3-((10Z,13E,15E)-heptadeca-10,13,15-trien-1-
yl)benzene-1,2-diol and the remainder of the extract is composed of similar diols with slight
differences in the saturation of the C-17 side chain [6-8].
As illustrated in Scheme 4.1, aliphatic: 1,6-hexamethylene diisocyanate (HMDI),
cycloaliphatic: 4,4’-dicyclohexylmethane diisocyanate (H12MDI) and aromatic: 4,4’-
diphenylmethane diisocyanate (4,4'-MDI) were utilized in this study to develop novel PUs with
79
laccol. Isocyanate group has cumulative double bonds; R-N=C=O and its reactivity is directed by
the positive character of the carbon atom (Scheme 4.1). If the R group is an aromatic substance,
the negative charge can delocalize and becomes more reactive compared to aliphatic or
cycloaliphatic isocyanates [1,3]. Therefore, aromatic isocyanate based urethane products dry
faster and developed cure properties faster than the aliphatic isocyanate based urethanes. In
contrast, aromatic isocyanate based urethanes can easily oxidize; specially after being exposed to
UV light compared to aliphatic isocyanate based urethanes, hence exterior coatings are
preferably developed using aliphatic isocyanate based urethanes [3].
Organometallic catalysts are widely used to synthesize PUs because of their strong
gelation activity. Generally these catalysts are much more effective in formation of aliphatic
based isocyanate-hydroxyl reaction compared to aromatic based isocyanate-hydroxyl reaction.
Despite of development in various metal based catalysts, inorganic and organic tin compounds
are still commonly involved in the PU synthesis. Most organotin catalysts are sensitive to
moisture and maintaining a moist free environment throughout the reaction process is very
important. In this study Tin(II) 2-ethylhexanoate was used as catalyst to facilitate our PU
synthesis because of its higher activity [9].
Depending on the diisocyanate and the polyol involved, thermal stability and the
crystalline properties of the PUs are differentiated. PUs are thermally stable polymers and some
PUs show higher thermal degradation temperatures above 250⁰C. The onset degradation
temperature of urethane bond depends on the types of used isocyanate used and polyol [10]. In
conventional PUs have hard (HS) and soft (SS) segments. Usually HS contains diisocyanate and
a low molecular weight diol which acts as a chain extender. SS contains hydroxyl terminated
oligomers such as polyesters, polyethers or polycarbonates. Hydrogen bonding domains consist
80
within the HS can act as a 'virtual' (physical) crosslinking platform. Because of this,
processability of PUs is greatly increased [2,10-12]. The N–H stretching vibration can be
observed in the IR region of 3500–3200 cm-1
and C=O stretching vibration can be observed in
1750–1600 cm-1
region [12]. Hydrogen bonding related to N–H and C=O could be observed
clearly in these regions for synthesized PUs. Different diisocyanates have different effects to the
morphology of PU. Physical cross links also changes accordingly. Hence, packing of the material
changes and these changes could be observed through Powder X-ray Analysis (PXRD), micro
hardness, and swelling tests. Thermal stability of PUs also changes with varying isocyanates and
this could be analyzed through differential scanning calorimetry (DSC), thermalgravimetry
(TGA) and rheology.
In this paper, novel laccol based PUs prepared with different diisocyanates were analyzed
and characterized. Influence of the cycloaliphatic and aromatic diisocyanate was more prominent
compared to aliphatic diisocyanate for the synthesized PUs. Temperature treatment further
improved the overall material quality by enhancing thermal stability, crosslink density and
hardness. Available long side chain of laccol can facilitate the physical crosslinking and provides
a proper platform for further modifications because of the unsaturation present. Therefore, these
novel PUs could become potent candidates for thermal insulation and energy storing applications
[11,13,14].
81
Scheme 4.1: Generic mechanism for PU formation with diisocyanate [1,3]
82
4.2 Experimental Section
4.2.1 Materials
The three different diisocyanates namely hexa methylene diisocyanate (HMDI), 4,4'–methylene
bis(cyclohexyl isocyanate) (H12MDI), 4,4'–methylene bis(phenyl isocyanate) (4,4'–MDI), 99.8%
Toluene (C7H8) and Tin(II) 2-ethyl hexanoate (Sn catalyst) were purchased from Sigma Aldrich.
Lacquer sap was imported from Viet Lacquer Interior Co. Ltd in Vietnam. Reagent grade
dichloromethane (CH2Cl2) and acetone (CH3COCH3) were used as solvents in this study.
4.2.2 Preparation Procedures
Laccol was extracted using acetone as described in our previously published article [15]. All the
diisocyanate samples and reagent grade solvents were used as received without further
purification. Generic reaction mechanism for PU synthesizing process with metal ion catalyst
was illustrated in Scheme 4.1 [1,3].
4.2.2.1 Synthesis of laccol and HMDI polyurethane (LH-1):
To a dichloromethane (DCM) 5.0 ml solvent, 10.0 g of laccol was added while stirring in a
~50⁰C water bath. A 5.2 g of HMDI slowly added to the mixture followed by 4 drops of Sn
catalyst and stirring was continued for half an hour. HMDI amount was calculated maintaining
the 1:1 molar ratio between laccol and HMDI. Once the sample gets considerably viscous, it was
collected and left inside the fume hood for one hour. Then the sample was transferred to vacuum
oven at ~60⁰C for 3 days and lastly to the dry oven at 100⁰C for one week (post curing).
83
4.2.2.2 Synthesis of laccol and H12MDI polyurethane (LH-2):
To a DCM 5.0 ml solvent, 10.0 g of laccol was added while stirring in a ~45⁰C water bath. A 7.4
g of H12MDI was slowly added to the mixture followed by 4 drops of Sn catalyst and stirring was
continued for 25 minutes. H12MDI amount was calculated maintaining the 1:1 molar ratio
between laccol and H12MDI. Once the sample gets considerably viscous, it was collected and left
inside the fume hood for one hour. Then the sample was transferred to vacuum oven at ~60⁰C for
3 days and lastly to the dry oven at 100⁰C for one week (post curing).
4.2.2.3 Synthesis of laccol and 4,4'–MDI polyurethane (LH-3):
To a DCM 10.0 ml solvent, 7.45 g of 4,4'–MDI was added and dissolved completely. This
mixture was then added slowly to 10.0 g of laccol while stirring in a ~45⁰C water bath. Four
drops of Sn catalyst was added lastly and stirring was continued for 15 minutes. 4,4'–MDI
amount was calculated maintaining the 1:1 molar ratio between laccol and 4,4'–MDI. Once the
sample gets considerably viscous, it was collected and left inside the fume hood for one hour.
Then the sample was transferred to vacuum oven at ~60⁰C for 3 days and lastly to the dry oven
at 100⁰C for one week (post curing).
4.2.3 Characterization Methods
Synthesized PUs were characterized using different techniques as described as follows.
Functional group identification, thermal and mechanical properties investigation were conducted
to understand the newly synthesized material behavior.
84
4.2.3.1 Fourier Transform Infra-Red (FTIR) Analysis
FTIR analysis was conducted on the prepared thin films of PU solid samples utilizing UATR
Two (Perkin Elmer) spectrometer with scan range from 400 cm-1
to 4000 cm-1
, 16 average scans
and at 4 cm-1
resolution.
4.2.3.2 Nuclear Magnetic Resonance Spectroscopy (NMR)
Prepared laccol based PUs were difficult to dissolve, therefore, partially solubilized samples in
chloroform-d solvent were utilized in the NMR analysis. A Varian INOVA 400 spectrometer
was used having a spin set and maintained at 20 Hz, under 298 K controlled temperature with d1
relaxation time of 2.000 seconds and 16 transients used in block sizes of 8.
4.2.3.3 Differential Scanning Colorimetry (DSC)
Identification of glass transition temperature (Tg) of synthesized PUs was carried out using
Differential Scanning Calorimeter model 2920 of TA Instruments. The sample cell of the
instrument has controlled 70 ml/min dry nitrogen gas flow rate and liquid nitrogen cooling
accessory (LNCA) was coupled to achieve the required low temperatures. Indium was utilized
to temperature calibration of the instrument and three different ramp rates were maintained
(10⁰C/min, 20⁰C/min, 30⁰C/min) to identify the proper Tg region. Prepared PU samples were
first cooled down to -70⁰C, heated up to +300⁰C, again cooled down to -70⁰C and heated for
second time to +300⁰C (two cycles of cooling and heating).
85
4.2.3.4 Dynamic Mechanical Analysis [16]
Carver® hydraulic press was utilized to mold synthesized PU samples into rectangular bars
having 10.5 mm width, 50 mm length and 2 mm thickness. This press has a slow cooling rate
from higher temperatures to room temperature with applied pressure. Isothermal strain sweep
experiment was conducted at -50⁰C utilizing AR 2000 rheometer (TA Instruments, USA) to
identify the linear viscoelastic region (LVR) for synthesized PU samples and 3.5% strain was
selected to characterize the samples. The temperature ramp experiment was conducted in
oscillation mode to identify the glass transition temperature (Tg) accurately and used ramp
conditions were -100⁰C to 300⁰C at 10⁰C/min rate with liquid nitrogen for cooling.
Further, using the rectangular bars molded from PU samples, a frequency sweep experiment was
conducted by adjusting the parameters as follows in the rheometer. Frequency range was set
from 0.1 Hz to 10.0 Hz, strained maintained at 3.5% and starting temperatures were changed
accordingly to specific samples providing 10⁰C increments per run until the sample collapse.
Starting temperatures for LH-1 sample was 0⁰C, LH-2 sample was 90⁰C and LH-3 sample was
70⁰C. For each sample, activation energy associated with glass transition region was calculated
using the frequency sweep data using equation (1).
∆𝐸𝑎 = (2.303) (𝐶1
𝐶2) 𝑅𝑇2 (1)
86
4.2.3.5 Thermal Gravimetric Analysis (TGA)
Maintaining the temperature ramp rate at 10⁰C/min in air, weight loss with respect to
temperature was measured using TA Q50 model of TGA. The temperature range was set from
room temperature (~22⁰C) to 700⁰C for testing articles.
4.2.3.6 Micro Hardness
Test samples were molded using Carver® laboratory press (model C) having the disc shaped of
2.54 cm width and 0.25 cm thickness. Prepared samples were tested utilizing Leica VMHT MOT
micro hardness tester under room temperature (~22⁰C). Eight readings were collected from both
surfaces of the sample and were averaged to obtain the final value. Indenting load was
maintained at 300 gf with 15 seconds contact time for each PU sample.
4.2.3.7 Powder X-ray Analysis (PXRD)
X-ray diffraction patterns were collected for each PU sample to identify the degree of
crystallization and packing using the Bruker D8 Focus X-ray diffractometer. Data collecting
range was set from 2⁰ to 70⁰ with a step of 0.020⁰ at 25⁰C [17].
4.2.3.8 Swelling Analysis [18,19]
From each PU sample, specimens were obtained having the exact weight (MI) for the swelling
analysis using precision balance. These specimens were immersed in ~30 ml toluene containing
flasks separately for 72 hours at room temperature (~22⁰C). After the required time frame
87
elapsed, remaining toluene solvent was decanted and the adhering solvent to the specimens was
dried by short contact with filter paper. The weight of the swollen PUs (MII) was measured
immediately after the drying process. Following the equation 2 illustrated in here, percent weight
gain was calculated.
𝑊𝑒𝑖𝑔ℎ𝑡 𝑔𝑎𝑖𝑛 [%] = (𝑀𝐼𝐼
𝑀𝐼− 1) 100, 𝑀𝐼𝐼 ≥ 𝑀𝐼 (2)
4.3 Results and Discussion
Synthesized novel laccol based PUs were characterized using FTIR, NMR, DSC, Rheology,
TGA, Micro hardness, PXRD and swelling tests as follows. Results were discussed in detail
hereafter to understand the properties of these developed materials. Resulting materials exhibited
promising attributes because of incorporating different diisocyanates to synthesize laccol based
PUs.
4.3.1 FTIR Analysis
Identification of PU synthesis process and reaction propagation was completed using IR analysis.
According to the results observed as in Figure 4.1, N–H stretching vibrations were visible near
the 3450 – 3440 cm-1
IR region and associated (hydrogen bonded) N–H stretching vibrations
observed around 3300 – 3350 cm-1
region [4,11,12,20-22].
88
Figure 4.1: IR spectra of synthesized LH-1, LH-2 and LH-3 samples
Similarly, non-associated C=O stretching vibration observed around 1720 cm-1
and associated
(hydrogen bonded) C=O stretching vibration observed around 1640 cm-1
IR region. Further the
disappearance of 2270 cm-1
peak related to isocyanate is evident of the complete use of
isocyanate in reaction and successful formation of targeted laccol based PUs namely LH-1, LH-2
and LH-3 [4,11,12,20-22]. In this synthesized PUs possible hydrogen bond formations could be
observed between urethane N–H (proton donor) and urethane C=O or –C–O–C– group (proton
acceptor) [21,23]. Also out of plane stretching vibrations corresponds to C–N bond (amide)
observed around 1520 – 1545 cm-1
IR region [21,22]. As shown in Figure 4.1, these observations
clearly are evidence of the formation of laccol based PUs and hydrogen bond formation in
synthesized PUs.
89
Additionally, the bending vibrations corresponding to trans conjugated C=C and cis C=C which
presented in C-17 side chain of laccol were also observed in the regions of 988, 968 cm-1
and
736 cm-1
[6,24-27]. Availability of this side chain is possibly involved in crosslinking process
because of its active sites (C=C) and length. Physical crosslinking occurs due to the secondary
interactions such as hydrogen bonding, hydrophobic interactions, ionic interactions, π–π stacking
(mainly in aromatic structures) and even entanglement of long chains [28]. Alterations observed
in 988, 968 cm-1
and 736 cm-1
IR regions evident the possible crosslinking in synthesized PUs.
These laccol based novel PUs were treated under higher temperature for molding purposes
(Figure 4.2-b) and molded samples were tested in rheometer (temp ramp experiment) for
characterization purposes (Figure 4.2-a). Alterations occurred because of these temperature
treatments were further studied through IR analysis to better understand the materials. According
to the obtained results as shown in Figure 4.2(a), major differences occurred in IR regions after
rheology (temp ramp) experiment. In this scenario temperature was increased from -100⁰C to
300⁰C with 10⁰C/min increments. When temperature increased the corresponding N–H and C=O
stretching vibration frequencies were shifted to higher frequencies due to the elongation of
hydrogen bonds [12,20,21] for LH-1, LH-2, LH-3 samples and became less well defined as
shown in Figure 4.2(a). After the temp ramp experiment, associated C=O stretching vibration
became more prominent in all samples and more ordered hydrogen bonding observed in LH-3
[12]. Feasibility of forming intermolecular hydrogen bonds is clearly observed in this IR analysis
after rheology experiment. Further, the IR region related to unsaturated laccol side chain
underwent significant changes after rheology experiment and this was possibly due to the
physical crosslinking.
90
Figure 4.2: IR spectra for; (a) Synthesized PUs before & after rheology (temp ramp) experiment,
(b) Synthesized PUs before & after molding
91
In the process of molding, used temperature was ~177⁰C (350⁰F). With respect to observed IR
data in Figure 4.2(b), not much difference in hydrogen bonding was detected before and after
molding. Therefore, this temperature is most appropriate to process synthesized laccol based PUs
according to our observations.
4.3.2 NMR Analysis
Cured PU samples were hardly dissolved in CDCl3. Therefore, partially solubilize PUs in CDCl3
were utilized in proton NMR analysis. According to the results obtained in Figure 4.3, urethane
linkages were formed during the reaction for all synthesized PU samples. At 5.15 ppm region
peak related to –OOCNH– was observed for LH-1, LH-2 and LH-3. For LH-1 sample, –CH2
next to –NH group was observed around 3.3 ppm region and methylene groups denoted as d-g
observed around 1.0 ppm. Signature region for laccol could be seen in the region between 1.0
ppm to 2.5 ppm with some overlapping peaks for PU as well. Unsaturation present in laccol side
chain clearly observed in the region between 5.25 ppm to 5.75 ppm [15,29-31]. The peak related
to –CH2 group present in LH-2 and LH-3 denoted as g and e was observed in the region of 1.0
ppm respectively. The –CH group (in the phenyl ring of 4,4'–MDI) denoted as c and d in LH-3
was observed in 6.6 ppm region with overlapping peaks related to laccol phenyl group. A small
amount of acetone was observed as an impurity in these samples which was used to extract
laccol from Vietnamese lacquer sap. These observations presented in Figure 4.3, are further
evidence of the successful formation of laccol based PUs with different diisocyanate groups.
92
Figure 4.3: NMR spectra of LH-1, LH-2 and LH-3; *Acetone
93
4.3.3 DSC Analysis
Synthesized PUs were analyzed to identify the glass transition temperature (Tg) and all samples
were characterized using three different ramp rates (10⁰C/min, 20⁰C/min, 30⁰C/min) to elucidate
the Tg region. Observed data for LH-1 is more accurately represented compared to other two
materials as illustrated in Figure 4.4 and scale of the graph is manually adjusted from -60⁰C to
100⁰C to avoid disturbances. After the 100⁰C temperature mark, data curves representing LH-2
and LH-3 samples were somewhat distorted and several peaks (broad/narrow) overlapped the Tg
region. No crystallinity peaks were observed for samples, even though the powder X-ray data
show some narrow peaks as described in section 3.7. With the increment of ramp rate, the Tg
region was shifted to higher temperature. This phenomenon was used to identify the proper Tg
region for novel PUs. From the DSC data obtained, proper operating window for temperature
was identified and this was utilized in rheometer to further analyze these PU samples and results
were described in section 4.3.4. LH-1 consists of linear diisocyanate group which can possibly
facilitate less hindrance movement of polymer molecules at low glass transition temperature
(52.51⁰C). Alterations occurred in DSC curves for LH-2 and LH-3 samples (contained cyclic and
aromatic isocyanate groups respectively) in the temperature range of 100⁰C to 300⁰C may
possibly due to the hydrogen bond formation. This possibility could further confirmed from the
IR data illustrated in Figure 4.2. It is stipulated that hydrogen bond formation is an exothermic
process [10,11,21].
94
Figure 4.4: DSC data for LH-1, LH-2 and LH-3 at 30⁰C/min ramp rate
4.3.4 Dynamic Mechanical Analysis
Prepared PU samples were molded to rectangular bars as described in section 4.2.4 and analyzed
utilizing rheometer. Linear viscoelastic region (LVR) was identified for PU samples by
conducting strain sweep experiment and obtained value 3.5% was maintained throughout other
experiments. Using temp ramp experiment Tg values for samples were obtained and
corresponding activation energies at Tg region was calculated with equation 1. Frequency sweep
data obtained for samples were incorporated to Time Temperature Superposition software to
create WLF graph which utilized later to calculate activation energies. In equation (1), C1 and C2
95
represent material constants which obtained from WLF graph, R is universal gas constant (8.314
Jmol-1
K-1
), T is temperature in Kelvin and Ea is activation energy.
Figure 4.5: Temp ramp experimental data for LH-2 and LH-3 to identify Tg
96
Figure 4.6: LH-1 (a) WLF plot created from TTS for activation energy calculation and (b)
Master curve developed from WLF graph
97
Tg values of three samples are arranged in increasing order as follows; LH-1<LH-3<LH-2 and
activation energies are increased as LH-1<LH-2<LH-3 (Table 4.1). Glass transition temperature
(Tg) values obtained for synthesized novel PUs are generally high specifically LH-2 and LH-3
compared to reported literature. This is possible due to the used laccol and the diisocyanate
formulations. Freely available side chain of laccol can possibly enhance the crosslinking which
lead to higher Tg values as a result. Also the increase amount of hydrogen bonding can elevate
the Tg of samples because of the restriction of free molecular movement [11]. Tg for LH-2 and
LH-3 are higher than the LH-1. LH-2 and LH-3 PU samples contain cyclic H12MDI and aromatic
4,4'-MDI diisocyanate groups respectively. According to the results illustrated in Figure 4.5, Tg
for LH-2 is 162.0⁰C and LH-3 is 138.9⁰C. The ring structures present in the diisocyanate groups
of LH-2 and LH-3 contributed to higher Tg values because of the physical crosslinking.
Hydrogen bonding, π – π stacking (aromatic structure) and even long side chain (in laccol)
entanglements as physical crosslinks can involve to increase the Tg value. Hence more energy is
required to initiate a slippage in polymer material and it leads to increase of activation energy
related to Tg. In Figure 4.5, G' is storage modulus, G'' is loss modulus and tan(δ) is loss factor are
plotted as function of temperature. With high temperature treatment (after 200⁰C), tan(δ) curve is
changing in the rubbery region due to the further curing of materials. This phenomenon was
observed for all PU samples. Further curing occurs through crosslink formation at higher
temperatures.
98
Table 4.1: Tg values and corresponding ΔE values obtained from analysis
However, comparing the results illustrated in Table 4.1, Tg of LH-3 is lower than LH-2, but
activation energy of LH-3 is higher than LH-2. This could possibly be due to the formation of
smaller molecular weight polymer molecules in large amounts compared to LH-2. Another
possibility could be due to the repulsion between aromatic ring in 4,4'-MDI and the available
long side chain of laccol, hinders the formation of long polymer molecule. Therefore, the chain
slippage occurs at lower temperature in LH-3, but collectively required higher activation energy
due to large amount for the whole material. Developed WLF curves from time temperature
superposition (TTS) software which utilized to calculate activation energy for LH-1 is illustrated
in Figure 4.6 as a reference. Master curve was also constructed accordingly after the assignment
of WLF curve. For all PU formulations, the obtained graphs have similar pattern as Figure 4.6
and only one formulation is demonstrated (Figure 4.6) here as an example.
4.3.5 TG Analysis
Thermal stability of synthesized laccol based PU materials were analyzed through TGA at
10⁰C/min ramp rate. According to the results illustrated in Figure 4.7, degradation of PU
materials were divided mainly into two stages. In first stage urethane bonds degraded and later
99
the ester groups related to polyol degraded. It is stated that urethane bonds are relatively
thermally unstable [10,22,32-35]. LH-1 has the highest thermal decomposition temperature
(260⁰C) compared to LH-2 and LH-3 (200⁰C and 212⁰C respectively). Linear diisocyanate group
present in LH-1 could possibly facilitate the ordered packing of polymer molecules with physical
crosslinks which can lead to the higher thermal stability overall. According to the results
increasing order of initial degradation temperature for PU materials can arrange as LH-3<LH-
2<LH-1. The amount of residue remained after 600⁰C for LH-1, LH-2 and LH-3 are 15%, 7.5%
and 18% respectively. Highest residue obtained for LH-3 which has an aromatic diisocyanate
groups. Presence of aromatic diisocyanate groups can lead to the possible occurrence of π – π
stacking apart from other physical crosslinks. This may influence the thermal stability of
materials at higher temperatures.
Figure 4.7: TG curves for synthesized LH-1, LH-2 and LH-3 samples
100
4.3.6 Micro hardness
Micro hardness of the synthesized laccol based PUs were analyzed using disc/rectangular shaped
molds. According to the results illustrated in Figure 4.8, hardness increases with the change of
diisocyanate used to synthesize PUs. Highest hardness value (26.55) observed for LH-3
consisting aromatic isocyanate group. Possibility of forming different types of physical
crosslinks such as hydrogen bonding, π – π stacking and chain entanglements could increase
hardness of this LH-3 material. After rheology temp ramp experiment, micro hardness of the
resulting samples was analyzed. Obtained data shows the increment of hardness for all PUs.
These results suggest the formation of more physical crosslinks after temperature increments.
This phenomenon was further supported by the IR analysis data discussed earlier in section 4.3.1
specifically related to Figure 4.2.
Figure 4.8: Micro hardness data for LH-1, LH-2 and LH-3
101
4.3.7 PXRD Analysis
Morphology of synthesized PUs was analyzed using powder X-ray diffraction technique. This
technique determines the long range order of material with respect to short range interactions
[2,11,12,22,32]. According to the results shown in Figure 4.9, all PUs show broad peaks at 2θ
angles indicating some degree of crystallinity [32]. LH-1 shows broad peaks around 21⁰ and 24⁰
compared to LH-2 (18⁰) and LH-3 (19⁰). It is reasonable to stipulate that linear diisocyanate in
LH-1 possibly enhance the more ordered packing compared to other two PU samples.
Synthesized PU samples in this study show more ordered packing as illustrated in Figure 4.9.
This is possibly due to the physical crosslinks such as hydrogen bonding, π – π stacking and long
chain entanglements appeared in the synthesized PU materials.
Figure 4.9: PXRD data for synthesized PU samples (LH-1, LH-2, LH-3)
102
4.3.8 Swelling Analysis
Formation of physical crosslinks enhances the properties of synthesized PUs and this was
analyzed through swelling of the polymers. Equation 2 illustrated in section 2.3.8 utilized to
calculate percent weight gain for each PU material. If the solvent uptake of the PU materials are
higher, this will lead to less crosslinks formation and vice versa [18,19]. According to the
obtained results, LH-1 shows the higher %weight gain (12.96) hence lesser number of crosslinks.
Even this material has the more ordered packing, amount of physical crosslinks present in the
material are lower compared to LH-2 and LH-3. The latter consists of cycloaliphatic and
aromatic diisocyanate groups in the PUs and density of physical crosslinks are higher. Percent
weight gains of LH-2 and LH-3 are 3.18 and 4.70 respectively. Because of the ring structures
present in these materials, π – π stacking and other physical interactions are greatly increased
which influenced the overall material quality.
4.4 Conclusions
Novel laccol based PUs were successfully synthesized and characterized utilizing different
methods to identify their promising properties. The laccol extracted from Vietnamese lacquer sap
acted as the polyol component and reacted with three different diisocyanates (aliphatic,
cycloaliphatic and aromatic) in the presence of Tin(II) 2-ethylhexanoate catalyst. IR data
obtained for resulting PUs clearly indicated the formation of hydrogen bonding in the regions
depicted to N–H and C=O vibrations. With increase of temperature, it shows the peaks related to
N–H (3326 cm-1
) and C=O (1652 cm-1
) shifting to higher wave numbers and molding
temperature (~177⁰C) used in this study does not affect the overall quality of the material. NMR
data also confirmed the formation of urethane linkages and this data is evidence of the successful
103
development of laccol based PUs. Glass transition temperature (Tg) of the PUs were identified
through DSC and rheology analysis. Highest activation energy related to Tg was observed for
LH-3 and physical crosslinks formation mainly contributed to this fact. Ring structures present in
LH-2 and LH-3 enhance the physical crosslinking (hydrogen bonding, π – π stacking and long
side chain entanglements) and this phenomenon confirmed through the analysis of PXRD, micro
hardness and swelling techniques. According to observed results through characterization
techniques, the properties of synthesized laccol based novel PUs were influenced by used
diisocyanates (aliphatic HMDI, cycloaliphatic H12MDI and aromatic 4,4'-MDI) groups and high
temperature treatment. Also the side chain in laccol structure (meta position in ring) more or less
is involved with physical crosslinking and also provides a better platform to further
modifications due to unsaturation presence. Successful formation and characterization of novel
laccol based PUs were achieved in this study. Promising properties observed for these materials
gain qualification as potent candidates of industrial applications such as thermal insulation and
energy storing.
4.5 Acknowledgement
Authors gratefully acknowledge Professor Lukasz Wojtas in Chemistry Department of
University of South Florida, for analyzing powder X-ray data.
4.6 References
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107
CHAPTER FIVE
CONCLUSIONS
Laccol extracted from Vietnamese lacquer sap was successfully polymerized via cationic
polymerization process. The initiator used, AlCl3.EtOAc is identified as most suitable for this
process. Conjugated double bonds present in the laccol side chain mainly involve in the cationic
polymerization process and crosslinks also formed because of available active sites (hydroxyl
groups, cis double bond, reactive protons available in laccol phenyl ring). These crosslinks
promoted to form three dimensional polymer networks which are hard in nature and less soluble.
Obtained IR and NMR data confirmed the formation of these polymers. Laccol based
copolymers were also produced utilizing styrene and d-limonene. Cationic polymerization is
utilized for this process and synthesized materials were high in quality with promising attributes.
Developed laccol based polymers and copolymers were exposed to gamma radiation and studied
their alterations. According to the results after gamma irradiation, materials were further cured
without deteriorating. IR data, rheology data, shore hardness data, PXRD data and swelling
analysis data confirmed the above statement. Hardness of the materials was improved
significantly after gamma irradiation and solubility of materials was reduced accordingly. D-
limonene extracted from orange peels was utilized in this study to produce laccol:d-limonene
copolymers. This is an environmental friendly approach to develop sustainable copolymer
materials. Apart from the above, this attempt could somewhat help to regulate citrus waste
accumulation due to use of waste products in new material synthesis. Developed laccol based
108
polymers and copolymers are prominent candidates to use as protective coatings/shields against
gamma radiation rich environments such as nuclear reactors, outer space operations, medicinal
sterilization plants and commercial irradiators.
Laccol based polyurethanes (PUs) were able to produced successfully with the use of Tin (II)
catalyst. Amide linkages were formed between hydroxyl groups present in laccol and isocyanate
groups and this was confirmed by the results obtained from IR and NMR data. Three different
diisocyanates were utilized in this process to develop polyurethanes and materials were
characterized to identify their properties. Hydrogen bonds formed through N–H and C=O
between polymer molecules were clearly observed in IR data. Physical and chemical crosslinks
were also present in this 3D polymer networks as shown in the results of swelling analysis, micro
hardness and PXRD. Further, neat packing arrangements of polymer molecules were observed
for all PUs with narrow peaks visible in PXRD data compare to amorphous regions obtained for
usual polymers. All the results and observations confirmed the fact that synthesis of laccol based
novel PUs was successful. This novel PUs could be potent candidates to use as thermal insulator
materials and as energy storing materials.
109
APPENDICES
110
Appendix A: USF Fair Use Worksheet for Chapter One
University of South Florida
USF Fair Use Worksheet
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a history of judicial decisions that recognized that unauthorized use of copyrighted materials
were "fair uses." The distinction between fair use and infringement may be unclear and not easily
defined. There is no specific number of words, lines, or notes that may safely be taken without
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content is likely to be considered to be a “fair use.”
Before you begin your fair use determination, ask yourself the following questions:
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If your answer to the above questions was no, then you should proceed with your fair use
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3. The amount and substantiality of the portion used in relation to the copyrighted work as a
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4. The effect of the use upon the potential market for, or value of, the copyrighted work
None of these factors are independently determinative of whether or not a use is likely to be
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LeEtta Schmidt, [email protected] and Drew Smith [email protected]
Reviewed by USF General Counsel 08/11/2015
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INSTRUCTIONS
Check all boxes that apply, and keep a copy of this form for your records. If you have questions,
please contact the USF General Counsel or your USF Tampa Library Copyright Librarian.
Name: Imalka Marasinghe Arachchilage Date: 3/23/2021
Class or Project: PhD Dissertation
Title of Copyrighted Work: Lacquer (https://en.wikipedia.org/wiki/Lacquer)
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Crews, Kenneth D. (2008) Fair use Checklist. Columbia University Libraries Copyright Advisory Office.
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Appendix B: License of Reproduced Material in Chapter Two
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Licensed Content Publisher John Wiley and Sons
Licensed Content Publication Polymer Engineering & Science
Licensed Content Title Synthesizing radiation‐hard polymer and copolymers using
laccol monomers extracted from lacquer tree
Toxicodendron succedanea via cationic polymerization
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subsequent breach by such other party.
This Agreement may not be assigned (including by operation of law or otherwise) by you
without WILEY's prior written consent.
Any fee required for this permission shall be non-refundable after thirty (30) days from
receipt by the CCC.
These terms and conditions together with CCC's Billing and Payment terms and
conditions (which are incorporated herein) form the entire agreement between you and
WILEY concerning this licensing transaction and (in the absence of fraud) supersedes all
prior agreements and representations of the parties, oral or written. This Agreement may
not be amended except in writing signed by both parties. This Agreement shall be
binding upon and inure to the benefit of the parties' successors, legal representatives, and
120
authorized assigns.
In the event of any conflict between your obligations established by these terms and
conditions and those established by CCC's Billing and Payment terms and conditions,
these terms and conditions shall prevail.
WILEY expressly reserves all rights not specifically granted in the combination of (i) the
license details provided by you and accepted in the course of this licensing transaction,
(ii) these terms and conditions and (iii) CCC's Billing and Payment terms and conditions.
This Agreement will be void if the Type of Use, Format, Circulation, or Requestor Type
was misrepresented during the licensing process.
This Agreement shall be governed by and construed in accordance with the laws of the
State of New York, USA, without regards to such state's conflict of law rules. Any legal
action, suit or proceeding arising out of or relating to these Terms and Conditions or the
breach thereof shall be instituted in a court of competent jurisdiction in New York
County in the State of New York in the United States of America and each party hereby
consents and submits to the personal jurisdiction of such court, waives any objection to
venue in such court and consents to service of process by registered or certified mail,
return receipt requested, at the last known address of such party.
WILEY OPEN ACCESS TERMS AND CONDITIONS
Wiley Publishes Open Access Articles in fully Open Access Journals and in Subscription
journals offering Online Open. Although most of the fully Open Access journals publish open
access articles under the terms of the Creative Commons Attribution (CC BY) License only, the
subscription journals and a few of the Open Access Journals offer a choice of Creative Commons
121
Licenses. The license type is clearly identified on the article.
The Creative Commons Attribution License
The Creative Commons Attribution License (CC-BY) allows users to copy, distribute and
transmit an article, adapt the article and make commercial use of the article. The CC-BY license
permits commercial and non-
Creative Commons Attribution Non-Commercial License
The Creative Commons Attribution Non-Commercial (CC-BY-NC) License permits use,
distribution and reproduction in any medium, provided the original work is properly cited and is
not used for commercial purposes. (see below)
Creative Commons Attribution-Non-Commercial-No Derivs License
The Creative Commons Attribution Non-Commercial-No Derivs License (CC-BY-NC-ND)
permits use, distribution and reproduction in any medium, provided the original work is properly
cited, is not used for commercial purposes and no modifications or adaptations are made. (see
below)
Use by commercial "for-profit" organizations
Use of Wiley Open Access articles for commercial, promotional, or marketing purposes requires
further explicit permission from Wiley and will be subject to a fee.
122
Further details can be found on Wiley Online Library
http://olabout.wiley.com/WileyCDA/Section/id-410895.html
Other Terms and Conditions:
v1.10 Last updated September 2015
Questions? [email protected] or +1-855-239-3415 (toll free in the US) or +1-978-
646-2777.
123
Appendix C: License of Reproduced Material in Chapter Three
JOHN WILEY AND SONS LICENSE TERMS AND CONDITIONS
Jan 17, 2021
This Agreement between Mrs. Imalka Marasinghe Arachchilage ("You") and John Wiley and
Sons ("John Wiley and Sons") consists of your license details and the terms and conditions
provided by John Wiley and Sons and Copyright Clearance Center.
License Number 4991520805021
License date Jan 17, 2021
Licensed Content Publisher John Wiley and Sons
Licensed Content Publication Polymer Engineering & Science
Licensed Content Title Environmentally Friendly Radiation Hard d‐
Limonene and Laccol Copolymers Synthesized via
Cationic Copolymerization
Licensed Content Author Imalka H. A. M. Arachchilage, Milly K. Patel,
Joseph Basi, et al
Licensed Content Date Dec 30, 2019
Licensed Content Volume 60
Licensed Content Issue 3
Licensed Content Pages 12
Type of use Dissertation/Thesis
124
Requestor type Author of this Wiley article
Format Print and electronic
Portion Full article
Will you be translating? No
Title Synthesizing laccol based polymers/copolymers and
polyurethanes; characterization and their
applications
Institution name University of South Florida
Expected presentation date Apr 2021
Requestor Location Mrs. Imalka Marasinghe Arachchilage
14422 Reuter Strasse Cir Apt 1
TAMPA, FL 33613
United States
Attn: Mrs. Imalka Marasinghe Arachchilage
Publisher Tax ID EU826007151
Total 0.00 USD
Terms and Conditions
TERMS AND CONDITIONS
This copyrighted material is owned by or exclusively licensed to John Wiley & Sons, Inc. or one
of its group companies (each a "Wiley Company") or handled on behalf of a society with which a
Wiley Company has exclusive publishing rights in relation to a particular work(collectively
"WILEY"). By clicking "accept" in connection with completing this licensing transaction, you
125
agree that the following terms and conditions apply to this transaction (along with the billing and
payment terms and conditions established by the Copyright Clearance Center Inc., ("CCC's
Billing and Payment terms and conditions"), at the time that you opened your Rights Link
account (these are available at any time at http://myaccount.copyright.com).
Terms and Conditions
The materials you have requested permission to reproduce or reuse (the "Wiley
Materials") are protected by copyright.
You are hereby granted a personal, non-exclusive, non-sub licensable (on a stand-alone
basis), non-transferable, worldwide, limited license to reproduce the Wiley Materials for
the purpose specified in the licensing process. This license, and any CONTENT (PDF or
image file) purchased as part of your order, is for a one-time use only and limited to any
maximum distribution number specified in the license. The first instance of republication
or reuse granted by this license must be completed within two years of the date of the
grant of this license (although copies prepared before the end date may be distributed
thereafter). The Wiley Materials shall not be used in any other manner or for any other
purpose, beyond what is granted in the license. Permission is granted subject to an
appropriate acknowledgement given to the author, title of the material/book/journal and
the publisher. You shall also duplicate the copyright notice that appears in the Wiley
publication in your use of the Wiley Material. Permission is also granted on the
understanding that nowhere in the text is a previously published source acknowledged for
all or part of this Wiley Material. Any third party content is expressly excluded from this
permission.
126
With respect to the Wiley Materials, all rights are reserved. Except as expressly granted
by the terms of the license, no part of the Wiley Materials may be copied, modified,
adapted (except for minor reformatting required by the new Publication), translated,
reproduced, transferred or distributed, in any form or by any means, and no derivative
works may be made based on the Wiley Materials without the prior permission of the
respective copyright owner. For STM Signatory Publishers clearing permission under the
terms of the STM Permissions Guidelines only, the terms of the license are extended to
include subsequent editions and for editions in other languages, provided such editions
are for the work as a whole in situ and does not involve the separate exploitation of the
permitted figures or extracts, You may not alter, remove or suppress in any manner any
copyright, trademark or other notices displayed by the Wiley Materials. You may not
license, rent, sell, loan, lease, pledge, offer as security, transfer or assign the Wiley
Materials on a stand-alone basis, or any of the rights granted to you hereunder to any
other person.
The Wiley Materials and all of the intellectual property rights therein shall at all times
remain the exclusive property of John Wiley & Sons Inc, the Wiley Companies, or their
respective licensors, and your interest therein is only that of having possession of and the
right to reproduce the Wiley Materials pursuant to Section 2 herein during the
continuance of this Agreement. You agree that you own no right, title or interest in or to
the Wiley Materials or any of the intellectual property rights therein. You shall have no
rights hereunder other than the license as provided for above in Section 2. No right,
license or interest to any trademark, trade name, service mark or other branding
("Marks") of WILEY or its licensors is granted hereunder, and you agree that you shall
127
not assert any such right, license or interest with respect thereto
NEITHER WILEY NOR ITS LICENSORS MAKES ANY WARRANTY
ORREPRESENTATION OF ANY KIND TO YOU OR ANY THIRD PARTY,
EXPRESS, IMPLIED OR STATUTORY, WITH RESPECT TO THE MATERIALS OR
THE ACCURACY OF ANY INFORMATION CONTAINED IN THEMATERIALS,
INCLUDING, WITHOUT LIMITATION, ANY IMPLIEDWARRANTY OF
MERCHANTABILITY, ACCURACY, SATISFACTORYQUALITY, FITNESS FOR A
PARTICULAR PURPOSE, USABILITY,INTEGRATION OR NON-INFRINGEMENT
AND ALL SUCH WARRANTIESARE HEREBY EXCLUDED BY WILEY AND ITS
LICENSORS AND WAIVEDBY YOU.
WILEY shall have the right to terminate this Agreement immediately upon breach of this
Agreement by you.
You shall indemnify, defend and hold harmless WILEY, its Licensors and their
respective directors, officers, agents and employees, from and against any actual or
threatened claims, demands, causes of action or proceedings arising from any breach of
this Agreement by you.
IN NO EVENT SHALL WILEY OR ITS LICENSORS BE LIABLE TO YOU ORANY
OTHER PARTY OR ANY OTHER PERSON OR ENTITY FOR ANYSPECIAL,
CONSEQUENTIAL, INCIDENTAL, INDIRECT, EXEMPLARY ORPUNITIVE
DAMAGES, HOWEVER CAUSED, ARISING OUT OF OR INCONNECTION WITH
THE DOWNLOADING, PROVISIONING, VIEWING ORUSE OF THE MATERIALS
REGARDLESS OF THE FORM OF ACTION,WHETHER FOR BREACH OF
CONTRACT, BREACH OF WARRANTY, TORT, NEGLIGENCE, INFRINGEMENT
128
OR OTHERWISE (INCLUDING, WITHOUTLIMITATION, DAMAGES BASED ON
LOSS OF PROFITS, DATA, FILES, USE,BUSINESS OPPORTUNITY OR CLAIMS
OF THIRD PARTIES), AND WHETHEROR NOT THE PARTY HAS BEEN
ADVISED OF THE POSSIBILITY OF SUCHDAMAGES. THIS LIMITATION
SHALL APPLY NOTWITHSTANDING ANYFAILURE OF ESSENTIAL PURPOSE
OF ANY LIMITED REMEDY PROVIDED HEREIN.
Should any provision of this Agreement be held by a court of competent jurisdiction to be
illegal, invalid, or unenforceable, that provision shall be deemed amended to achieve as
nearly as possible the same economic effect as the original provision, and the legality,
validity and enforceability of the remaining provisions of this Agreement shall not be
affected or impaired thereby.
The failure of either party to enforce any term or condition of this Agreement shall not
constitute a waiver of either party's right to enforce each and every term and condition of
this Agreement. No breach under this agreement shall be deemed waived or excused by
either party unless such waiver or consent is in writing signed by the party granting such
waiver or consent. The waiver by or consent of a party to a breach of any provision of
this Agreement shall not operate or be construed as a waiver of or consent to any other or
subsequent breach by such other party.
This Agreement may not be assigned (including by operation of law or otherwise) by you
without WILEY's prior written consent.
Any fee required for this permission shall be non-refundable after thirty (30) days from
receipt by the CCC.
These terms and conditions together with CCC's Billing and Payment terms and
129
conditions (which are incorporated herein) form the entire agreement between you and
WILEY concerning this licensing transaction and (in the absence of fraud) supersedes all
prior agreements and representations of the parties, oral or written. This Agreement may
not be amended except in writing signed by both parties. This Agreement shall be
binding upon and inure to the benefit of the parties' successors, legal representatives, and
authorized assigns.
In the event of any conflict between your obligations established by these terms and
conditions and those established by CCC's Billing and Payment terms and conditions,
these terms and conditions shall prevail.
WILEY expressly reserves all rights not specifically granted in the combination of (i) the
license details provided by you and accepted in the course of this licensing transaction,
(ii) these terms and conditions and (iii) CCC's Billing and Payment terms and conditions.
This Agreement will be void if the Type of Use, Format, Circulation, or Requestor Type
was misrepresented during the licensing process.
This Agreement shall be governed by and construed in accordance with the laws of the
State of New York, USA, without regards to such state's conflict of law rules. Any legal
action, suit or proceeding arising out of or relating to these Terms and Conditions or the
breach thereof shall be instituted in a court of competent jurisdiction in New York
County in the State of New York in the United States of America and each party hereby
consents and submits to the personal jurisdiction of such court, waives any objection to
venue in such court and consents to service of process by registered or certified mail,
return receipt requested, at the last known address of such party.
130
WILEY OPEN ACCESS TERMS AND CONDITIONS
Wiley Publishes Open Access Articles in fully Open Access Journals and in Subscription
journals offering Online Open. Although most of the fully Open Access journals publish open
access articles under the terms of the Creative Commons Attribution (CC BY) License only, the
subscription journals and a few of the Open Access Journals offer a choice of Creative Commons
Licenses. The license type is clearly identified on the article.
The Creative Commons Attribution License
The Creative Commons Attribution License (CC-BY) allows users to copy, distribute and
transmit an article, adapt the article and make commercial use of the article. The CC-BY license
permits commercial and non-
Creative Commons Attribution Non-Commercial License
The Creative Commons Attribution Non-Commercial (CC-BY-NC) License permits use,
distribution and reproduction in any medium, provided the original work is properly cited and is
not used for commercial purposes. (see below)
Creative Commons Attribution-Non-Commercial-No Derivs License
The Creative Commons Attribution Non-Commercial-No Derivs License (CC-BY-NC-ND)
permits use, distribution and reproduction in any medium, provided the original work is properly
cited, is not used for commercial purposes and no modifications or adaptations are made. (see
below)
131
Use by commercial "for-profit" organizations
Use of Wiley Open Access articles for commercial, promotional, or marketing purposes requires
further explicit permission from Wiley and will be subject to a fee.
Further details can be found on Wiley Online Library
http://olabout.wiley.com/WileyCDA/Section/id-410895.html
Other Terms and Conditions:
v1.10 Last updated September 2015
Questions? [email protected] or +1-855-239-3415 (toll free in the US) or +1-978-
646-2777.
132
Appendix D: License of Reproduced Material in Chapter Four
JOHN WILEY AND SONS LICENSE TERMS AND CONDITIONS
Jan 17, 2021
This Agreement between Mrs. Imalka Marasinghe Arachchilage ("You") and John Wiley and
Sons ("John Wiley and Sons") consists of your license details and the terms and conditions
provided by John Wiley and Sons and Copyright Clearance Center.
License Number 4991521278492
License date Jan 17, 2021
Licensed Content Publisher John Wiley and Sons
Licensed Content Publication Polymer Engineering & Science
Licensed Content Title Synthesis and characterization of novel laccol based
polyurethanes
Licensed Content Author Imalka H. A. M. Arachchilage, Joseph Basi, Shahedul
Islam, et al
Licensed Content Date Dec 14, 2020
Licensed Content Volume 0
Licensed Content Issue 0
Licensed Content Pages 13
Type of use Dissertation/Thesis
Requestor type Author of this Wiley article
133
Format Print and electronic
Portion Full article
Will you be translating? No
Title Synthesizing laccol based polymers/copolymers and
polyurethanes; characterization and their applications
Institution name University of South Florida
Expected presentation date Apr 2021
Requestor Location Mrs. Imalka Marasinghe Arachchilage
14422 Reuter Strasse Cir Apt 1
TAMPA, FL 33613
United States
Attn: Mrs. Imalka Marasinghe Arachchilage
Publisher Tax ID EU826007151
Total 0.00 USD
Terms and Conditions
TERMS AND CONDITIONS
This copyrighted material is owned by or exclusively licensed to John Wiley & Sons, Inc. or one
of its group companies (each a "Wiley Company") or handled on behalf of a society with which a
Wiley Company has exclusive publishing rights in relation to a particular work(collectively
"WILEY"). By clicking "accept" in connection with completing this licensing transaction, you
agree that the following terms and conditions apply to this transaction(along with the billing and
payment terms and conditions established by the Copyright Clearance Center Inc., ("CCC's
134
Billing and Payment terms and conditions"), at the time that you opened your Rights Link
account (these are available at any time at http://myaccount.copyright.com).
Terms and Conditions
The materials you have requested permission to reproduce or reuse (the "Wiley
Materials") are protected by copyright.
You are hereby granted a personal, non-exclusive, non-sub licensable (on a stand-alone
basis), non-transferable, worldwide, limited license to reproduce the Wiley Materials for
the purpose specified in the licensing process. This license, and any CONTENT (PDF or
image file) purchased as part of your order, is for a one-time use only and limited to any
maximum distribution number specified in the license. The first instance of republication
or reuse granted by this license must be completed within two years of the date of the
grant of this license (although copies prepared before the end date may be distributed
thereafter). The Wiley Materials shall not be used in any other manner or for any other
purpose, beyond what is granted in the license. Permission is granted subject to an
appropriate acknowledgement given to the author, title of the material/book/journal and
the publisher. You shall also duplicate the copyright notice that appears in the Wiley
publication in your use of the Wiley Material. Permission is also granted on the
understanding that nowhere in the text is a previously published source acknowledged for
all or part of this Wiley Material. Any third party content is expressly excluded from this
permission.
With respect to the Wiley Materials, all rights are reserved. Except as expressly granted
by the terms of the license, no part of the Wiley Materials may be copied, modified,
135
adapted (except for minor reformatting required by the new Publication), translated,
reproduced, transferred or distributed, in any form or by any means, and no derivative
works may be made based on the Wiley Materials without the prior permission of the
respective copyright owner. For STM Signatory Publishers clearing permission under the
terms of the STM Permissions Guidelines only, the terms of the license are extended to
include subsequent editions and for editions in other languages, provided such editions
are for the work as a whole in situ and does not involve the separate exploitation of the
permitted figures or extracts, You may not alter, remove or suppress in any manner any
copyright, trademark or other notices displayed by the Wiley Materials. You may not
license, rent, sell, loan, lease, pledge, offer as security, transfer or assign the Wiley
Materials on a stand-alone basis, or any of the rights granted to you hereunder to any
other person.
The Wiley Materials and all of the intellectual property rights therein shall at all times
remain the exclusive property of John Wiley & Sons Inc, the Wiley Companies, or their
respective licensors, and your interest therein is only that of having possession of and the
right to reproduce the Wiley Materials pursuant to Section 2 herein during the
continuance of this Agreement. You agree that you own no right, title or interest in or to
the Wiley Materials or any of the intellectual property rights therein. You shall have no
rights hereunder other than the license as provided for above in Section 2. No right,
license or interest to any trademark, trade name, service mark or other branding("Marks")
of WILEY or its licensors is granted hereunder, and you agree that you shall not assert
any such right, license or interest with respect thereto
NEITHER WILEY NOR ITS LICENSORS MAKES ANY WARRANTY OR
136
REPRESENTATION OF ANY KIND TO YOU OR ANY THIRD PARTY, EXPRESS,
IMPLIED OR STATUTORY, WITH RESPECT TO THE MATERIALS OR THE
ACCURACY OF ANY INFORMATION CONTAINED IN THEMATERIALS,
INCLUDING, WITHOUT LIMITATION, ANY IMPLIED WARRANTY OF
MERCHANTABILITY, ACCURACY, SATISFACTORYQUALITY, FITNESS FOR A
PARTICULAR PURPOSE, USABILITY,INTEGRATION OR NON-INFRINGEMENT
AND ALL SUCH WARRANTIESARE HEREBY EXCLUDED BY WILEY AND ITS
LICENSORS AND WAIVEDBY YOU.
WILEY shall have the right to terminate this Agreement immediately upon breach of this
Agreement by you.
You shall indemnify, defend and hold harmless WILEY, its Licensors and their
respective directors, officers, agents and employees, from and against any actual or
threatened claims, demands, causes of action or proceedings arising from any breach of
this Agreement by you.
IN NO EVENT SHALL WILEY OR ITS LICENSORS BE LIABLE TO YOU ORANY
OTHER PARTY OR ANY OTHER PERSON OR ENTITY FOR ANYSPECIAL,
CONSEQUENTIAL, INCIDENTAL, INDIRECT, EXEMPLARY ORPUNITIVE
DAMAGES, HOWEVER CAUSED, ARISING OUT OF OR INCONNECTION WITH
THE DOWNLOADING, PROVISIONING, VIEWING ORUSE OF THE MATERIALS
REGARDLESS OF THE FORM OF ACTION,WHETHER FOR BREACH OF
CONTRACT, BREACH OF WARRANTY, TORT,NEGLIGENCE, INFRINGEMENT
OR OTHERWISE (INCLUDING, WITHOUTLIMITATION, DAMAGES BASED ON
LOSS OF PROFITS, DATA, FILES, USE,BUSINESS OPPORTUNITY OR CLAIMS
137
OF THIRD PARTIES), AND WHETHEROR NOT THE PARTY HAS BEEN
ADVISED OF THE POSSIBILITY OF SUCHDAMAGES. THIS LIMITATION
SHALL APPLY NOTWITHSTANDING ANYFAILURE OF ESSENTIAL PURPOSE
OF ANY LIMITED REMEDY PROVIDEDHEREIN.
Should any provision of this Agreement be held by a court of competent jurisdiction to be
illegal, invalid, or unenforceable, that provision shall be deemed amended to achieve as
nearly as possible the same economic effect as the original provision, and the legality,
validity and enforceability of the remaining provisions of this Agreement shall not be
affected or impaired thereby.
The failure of either party to enforce any term or condition of this Agreement shall not
constitute a waiver of either party's right to enforce each and every term and condition of
this Agreement. No breach under this agreement shall be deemed waived or excused by
either party unless such waiver or consent is in writing signed by the party granting such
waiver or consent. The waiver by or consent of a party to a breach of any provision of
this Agreement shall not operate or be construed as a waiver of or consent to any other or
subsequent breach by such other party.
This Agreement may not be assigned (including by operation of law or otherwise) by you
without WILEY's prior written consent.
Any fee required for this permission shall be non-refundable after thirty (30) days from
receipt by the CCC.
These terms and conditions together with CCC's Billing and Payment terms and
conditions (which are incorporated herein) form the entire agreement between you and
WILEY concerning this licensing transaction and (in the absence of fraud) supersedes all
138
prior agreements and representations of the parties, oral or written. This Agreement may
not be amended except in writing signed by both parties. This Agreement shall be
binding upon and inure to the benefit of the parties' successors, legal representatives, and
authorized assigns.
In the event of any conflict between your obligations established by these terms and
conditions and those established by CCC's Billing and Payment terms and conditions,
these terms and conditions shall prevail.
WILEY expressly reserves all rights not specifically granted in the combination of (i) the
license details provided by you and accepted in the course of this licensing transaction,
(ii) these terms and conditions and (iii) CCC's Billing and Payment terms and conditions.
This Agreement will be void if the Type of Use, Format, Circulation, or Requestor Type
was misrepresented during the licensing process.
This Agreement shall be governed by and construed in accordance with the laws of the
State of New York, USA, without regards to such state's conflict of law rules. Any legal
action, suit or proceeding arising out of or relating to these Terms and Conditions or the
breach thereof shall be instituted in a court of competent jurisdiction in New York
County in the State of New York in the United States of America and each party hereby
consents and submits to the personal jurisdiction of such court, waives any objection to
venue in such court and consents to service of process by registered or certified mail,
return receipt requested, at the last known address of such party.
WILEY OPEN ACCESS TERMS AND CONDITIONS
Wiley Publishes Open Access Articles in fully Open Access Journals and in Subscription
139
journals offering Online Open. Although most of the fully Open Access journals publish open
access articles under the terms of the Creative Commons Attribution (CC BY) License only, the
subscription journals and a few of the Open Access Journals offer a choice of Creative Commons
Licenses. The license type is clearly identified on the article.
The Creative Commons Attribution License
The Creative Commons Attribution License (CC-BY) allows users to copy, distribute and
transmit an article, adapt the article and make commercial use of the article. The CC-BY license
permits commercial and non-
Creative Commons Attribution Non-Commercial License
The Creative Commons Attribution Non-Commercial (CC-BY-NC) License permits use,
distribution and reproduction in any medium, provided the original work is properly cited and is
not used for commercial purposes.(see below)
Creative Commons Attribution-Non-Commercial-No Derivs License
The Creative Commons Attribution Non-Commercial-No Derivs License (CC-BY-NC-ND)
permits use, distribution and reproduction in any medium, provided the original work is properly
cited, is not used for commercial purposes and no modifications or adaptations are made. (see
below)
Use by commercial "for-profit" organizations
Use of Wiley Open Access articles for commercial, promotional, or marketing purposes requires
140
further explicit permission from Wiley and will be subject to a fee.
Further details can be found on Wiley Online Library
http://olabout.wiley.com/WileyCDA/Section/id-410895.html
Other Terms and Conditions:
v1.10 Last updated September 2015
Questions? [email protected] or +1-855-239-3415 (toll free in the US) or +1-978-
646-2777.
ABOUT THE AUTHOR
Imalka Marasinghe Arachchilage; a Sri Lankan national, obtained the BSc degree in Chemistry
from University of Colombo (UOC), Sri Lanka in 2010. Afterwards, she worked as a research
assistant for more than two years in Center of Analytical Research & Development (CARD) at
Department of Chemistry, UOC. During the time frame from 2014 to July 2015, she worked as a
scientific officer in National Dangerous Drugs Control Board (NDDCB) and as a research officer
in Medical Research Institute (MRI). In August 2015, she came to USA after obtaining an
opportunity to pursue PhD in Chemistry at University of South Florida (USF). Since then she is
staying in Tampa, Florida while working on her degree. She participated several in-campus and
out of campus meetings to present her research data. She is married and have a seven year old
son; Savindu Kankanige who is studying in second grade at Maniscalco Elementary School,
Lutz.