general approaches to polymer synthesis 1.additionchain growth polymerization of vinyl monomers ring...
TRANSCRIPT
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General Approaches to Polymer Synthesis
• 1. Addition Chain GrowthPolymerization of Vinyl Monomers
Ring Opening Polymerization Heterocylics Metathesis of Cyclic Olefins
2. Condensation Step Growth Polymerization of A-B or AA/BB Monomers3. Modification of Preformed Polymers
Polysaccharides
Peptides and Proteins Synthetic Precursors
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Major Developments in the 1950-60's
Living Polymerization (Anionic)• Mw/Mn 1• Blocks, telechelics and stars available
(Controlled molecular architecture)• Statistical Stereochemical Control• Statistical Compositions and Sequences• Severe functional group restrictions
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Ziegler-Natta (Metal-Coordinated) Polymerization
• Stereochemical Control
• Polydisperse products
• Statistical Compositions and Sequences
• Limited set of useful monomers, i.e. olefins
• SINGLE SITE CATALYSTS
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Additional Developments in the 1980's
• "Immortal" Polymerization (Cationic)– Mw/Mn 1.05– Blocks, telechelics, stars– (Controlled molecular architecture)– Statistical Compositions and Sequences– Severe functional group restrictions
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Free Radical Initiated Polymerization
• Controlled Free Radical Polymerization
• Broad range of monomers available
• Accurate control of molecular weight
• Mw/Mn 1.05 --Almost monodisperse
• Blocks, telechelics, stars
• (Controlled molecular architecture)
• Statistical Compositions and Sequences
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Current Strategies in Polymer Synthesis
• Objectives: Precise Macromolecular Design
• 1 . Control of: Molecular Weight– Molecular Weight Distribution– Composition– Sequence of repeat units– Stereochemistry
• 2. Versatility
–
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Genetic Approaches via Modified
Microorganisms • Monodisperse in MW
• Monodisperse in Composition
• Sequentially Uniform
• Stereochemically Pure
• Diverse set of functional groups possible through synthesis of novel amino acids
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Step-Growth or Condensation Polymerizations
Molecular Weight predicted by Carothers Equation:A-A + B-B -[A-B-]x + x C [A-A] = [B-B] = No# of functional groups remaining at anytime = N
Extent of reaction = pNo - N
p = _____ or N = No (1 - p) No
Degree of Polymerization, D.P. = No / N = 1 / (1 - p)
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Problems in Achieving High D. P.
1. Non-equivalence of functional groups
a. Monomer impurities1. Inert impurities (adjust stoichiometry)2. Monofunctional units terminate chain
b. Loss of end groups by degradation
c. Loss of end groups by side reactions with media
d. Physical losses e. Non-equivalent reactivity
f. Cyclization
. Unfavorable Equilibrium Constant
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Impact of percent reaction, p, on DP
if p = DP =
0.5 2
0.7 3.3
0.9 10
0.95 20
0.99 100
0.999 1000
Degree of Polymerization, D.P. = No / N = 1 / (1 - p)Assuming perfect stoichiometry
DPmax= (1 + r) / (1 - r) where r molar ratio of reactants
if r = [Diacid] / [diol] = 0.99, then DPmax= 199
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Cyclization
1. Thermodynamic stability
Rings of: 3,4,8 < 11 < 7, 12 << 5 << 6
2. Kinetic Control
Propagation more rapid than cyclization
Reduce probability of collision for rings 12
Non-reversible propagation process
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Equilibrium in Polyesterification
OH
O+
OH
O
O+
H2O
Keq =[-COO-] [H2O]
[COOH] [OH]=
(p [M]o)2
([M]o - p([M]o)2
Keq =p2
(1-p)2
Reaction in closed system
p = fraction esterified
p =K1/2
1-K1/2
DP = 1/(1-p) DP = 1 + K1/2
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Equilibrium in Polyesterification
Effect of Keq on extent of reaction and DP
Keq p Xn
0.01 0.1 1.11
1 0.5 2
16 0.8 5
81 0.9 10
361 0.95 20
9800 0.99 100
39,600 0.995 200
DP = 1 + K1/2
transesterification
esterification
amide formation
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Driving reaction to completion in open,
driven system Keq DP [H2O]
1 2 2.5
20 0.0132
50 0.00204
100 0.000505
200 0.000126
16 5 4.0
20 0.211
50 0.0327
100 0.0081
200 0.00201
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Types of Condensation Reactions
1. Polyesters
R OHHO R'OHHO
O O+
- n H2OR O R' O
O O
* *n
R OHHO R'OCH3H3CO
O O+
- n CH3OHR O R' O
O
* *n
O
OOO
R OHHO +
OOORHO OH
OOOR O **
-n H2O
n
O
O
(CH2)5HO C
O
OH (CH2)5 C
O
O
H2O
trace
-n H2O
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Preparation of Aromatic Polyesters
CC
O
O
O
O CH3H3C
HO-CH2CH2-OHxs
CC
O
O
O
O HH
Dimethyl Terephthalate (DMT)
Terephthalic Acid
CC
O
O
O
O
CH2CH2
CH2OH CH2OH
CH3OH+
CC
O
O
O
O
CH2CH2
CH2OH CH2OH
1 mm Hg 280 C
SbO3 or Ti(OR)4
CC
O
O
O
O
CH2
CH2O
+ HOCH2CH2OH
Stoichiometry and DP controlled by extent of glycol removed.
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Types of Condensation Reactions
R NH2H2N R'OHHO
O O+
- n H2OR
HN R' N
H
O O
* *n
R NH2H2N R'ClCl
O O+
- n HClR
HN R' N
H
O O
* *n
2. Polyamides
NH
O
(CH2)5H2N C
O
OH (CH2)5 C
O
NH
H2O
trace
-n H2O
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Polyamides via Condensation -- Nylon 66
C-(CH2)4-C
OO
OOH
H
CH2-(CH2)4
-CH2 NH2NH2
+
slight excess
C-(CH2)4-C
OO
O- O-
(CH2)4
CH2 CH2
NH3+ NH3
+
Nylon Salt
60% Slurry
200 C, 15 Atm. 1 hr
NH3+(CH2)6
-NH-C-(CH2)4-C-NH-(CH2)6
-NH-C-(CH2)4-C
O
OO
OO-
8-10
270-300 C, 1hr
- H2O
NH-(CH2)6-NH-C-(CH2)4
-C
O
O
Nylon 6 6
mp. 265C, Tg 50C, MW 12-15,000Unoriented elongation 780%
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Types of Condensation Polymers
R O C R' C On
O
Rn
O
R' C On
O
C
O
O
O
O n
Polyesters
Polycarbonates
Polyanhydrides
O O
Rn
Polyacetals
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Lexan Polycarbonate
CH3 CH3
OO --
Na+ Na++ Cl-C-Cl
O
Aq NaOH
CHCl2
CH3 CH3
OC
O
O
+ NaCl
xLexan
Interfacial Process
Tm = 270C,
Tg = 145-150C10-40 % Crystalline, Brittle Temp. - 10C
Ester Interchange
OC
O
O
+
CH3 CH3
OOH
H
1) 200 C/20mm
2) 300 C. <1mm
Lexan +
OH
No Solvent, Pure Polymer with MW > 30,000 Formed
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Types of Condensation Polymers
RHN R' N
HO
O
C
O
O
CH3
CH3
O
R
O O
SO O
Ar
polyurethanes polyphenylene oxide
polyarylenes
polyarylene ether sulfones
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Low Temperature Condensation Polymerization
• Interfacial or Solution in Polar Aprotic Solvents
Parameter Low Temp High Temp
Intermediates
Purity
Stoichiometry
Heat Stability
Structure
Cost
Moderate
Not Essential
Not Essential
Highly Reactive
High
High
Essential
Essential
Thermally stable
Moderate
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Interfacial or Solution Polymerization in Polar Aprotic Solvents (Con’t)
Conditions Low Temp High Temp
Time
Temperature
Pressure
Yield
By-products
Solvents
Minutes to hours
0 – 150 CAtmospheric
Low to moderate
Salts
Required
Hours to days
>250 CHigh to vacuum
Quantitative
Volatiles
None
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Applications of Low Temperature Condensations
• Prep. of Infusible Thermally Stable Polymers
• Prep. of Thermally Unstable Polymers
Prep. of Polymers Containing Functional Groups with Differing Reactivity
Formation of Block or Ordered Polymers(No equilibration of polymer in melt allowed)
Direct Production of Polymer Solutions for Coatings, Spinning into Fibers, Solvent Blending to form Composites
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Types of Condensation Polymers
RHN C R' C N
H
O O
NN
O
O
O
O
N
OO
N
Ar
N
SS
N
Ar
polyamidespolyimides
polybenzoxazolespolybenzthiazoles
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Aromatic Polyamides “Aramids”
NH2
NH2
+
C-Cl
C-Cl
O
O
SO O
DMF, LiCl
C-NH
C-NH
NH-C
C-NH
NH-CO
O
OO
O
Can be Dry Spun to FiberAs Spun: Elongation, 23-34%,Tenacity, 4.6-5.3 g/Denier
70% Strength Retained in Ionizing Radiation
Nomex M.p. > 350 C
Unique solvent combination
M-isomers favor formation of soluble polymers
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Polyimides for Electronic Applications
C-O
O-C
O
O
C-Cl
Cl-C
O
O
Cl-C-C-Cl
O
O syn and anti isomers
C-O
O-C
HO-C
C-OH
O
O O
O2 (CH
3)2CHOH
PMDA
ONH2
NH2
ODADMAC
C-O
O-C
O
O
C-NH
NH-C
O
O
O
N ON
O
O
O
O
heat or
amine catalyst
soluble
insoluble
O
O
O
O
O O
Kevlar
Fabricate in soluble form
Post treat to final form
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POLYETHERSULFONES
160 C
OO
OS
CH3O
2) CH3Cl
DMSO/Toluene
Cl S
Cl
O
O+
K+-O
O- K+
HO
OH
K+-O
O- K+
K2CO
3
Bis-Phenol-A
Molecular Weight = 65,000 - 250,000Amorphous Material, Tg 200C, Films pressed at 280C
Use Temperature -100 to + 175CStable in air to 500C, Self Extinguishing
Bis-nucleophile
Polymerize by SnAr2
Monofunctional terminator to stabilize polymer
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Polyphenylene Oxide (PPO)
R1
R2
OH + n/2 O2
R1
R2
O O
R2
R1
+ n H2O
cat
cat = N
NCH3
CH3N
CH3
CH3
3 : 1
or
10:1
Cu+
Amine Complex
Noryl is a blend with polystyrene
Oxidative Coupling Process
Mn 30,000 to 120,000Amorphous , Tg 210C Crystalline, Tm 270CBrittle point -170CThermally Stable to 370C
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Noryl is Unique Blend• Single Phase, Tg dependent upon composition• Maximum tensile strength at 80 wt% PPO• Other properties; volume fraction weighted average• Blend compatible with rubber modified polystyrene (high impact
resistance)
• Applications of Noryl Engineering Thermoplastics• Useful properties• High impact resistance• Flame retardant• High chemical stability• Low moisture absorbance (0.07%0• Use in appliance housings• Automobile dashboards• Radomes, fuse boxes, wiring splice devises