probing the bases of polymer glass transitions
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Probing the Bases of Polymer Glass Transitions
Miles Ndukwe
Millbrook High School
Raleigh, NC
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Polymers
• Sustaining Life
• Dominating
Commerce
Figure 1 - DNA
Figure 2 – Rubber tire
Figure 3 - Plastics
Figure 4 - Clothing
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Crystallinity
• Crystalline– Ordered
• Amorphous– Random
• Semi-crystalline– Consists of both
Figure 5 – Crystalline, amorphous, and semi-crystalline polymers
Crystalline
Amorphous
Semi-crystalline
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Glass Transition Temperature (Tg)
• Hard, brittle Soft, rubbery
Figure 6 – Visual representation of polymers’ actions at Tg.
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Factors Suggested to Affect Tg
1. Conformational flexibilities of individual polymer chain backbones
2. Sizes or steric bulk of side-chains
3. Interactions between polymer chains
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• Richardson, M. J. and Savill, N. G. “Derivation of Accurate Glass Transition Temperatures by Differential Scanning Calorimetry.” Polymer (1975). 753
• Kim, Y. W. et al. “Molecular Thermodynamic Model of the Glass Transition Temperature: Dependence on Molecular Weight.” Polymers for Advanced Technologies (2008). 944-946
• Makhiyanov, N. and Temnikova, E. V. “Glass-Transition Temperature and Microstructure of Polybutadienes.” Polymer Science (2010). 2102-2111
Review of Literature
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Statement of the Problem
The focus of this research is to determine if
differences in the contributions made by the
three structural factors cause and explain the
wide range of Tgs observed for structurally
different polymers.
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Research Questions
1. Why do polymers with different or even somewhat similar microstructures show different softening temperatures, sometimes ranging over several hundreds degrees Celsius?
2. Are each of the three factors (inherent conformational flexibilities of polymer chain backbones, sizes or steric bulk of side chains, and interactions between polymer chains) important in determining a polymer’s Tg?
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Hypothesis
If two amorphous polymers, both with nearly
identical inherent conformational flexibilities of
their polymer chain backbones (factor 1) and no
side chains (factor 2), differ in Tg, then it is caused by differences in the interactions between polymer chains (factor 3), because the other factors have been eliminated by their commonality.
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Materials and Methods
Materials
Salt Preparation
Melt Pre-Polymerization
Solid State Polymerization
• Co-polyamide‒ 1,6 Hexamethylenediamine‒ Adipic Acid‒ Sebacic Acid
• Co-polyester‒ 1,6 Hexanediol‒ Adipic Acid‒ Sebacic Acid
‒ Mixed monomers (homopolymers)‒ Mixed monomer salts (co-polymers)
Co-Polymers
Production Methods
Monomers
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Comparison of Polymers
1,6 Hexamethylenediamine
Adipic Acid
Nylon 6,6
Adipic Acid 1,6 Hexanediol
OHHO
Polyester 6,6
O O
Figure 7 – Formula of nylon 6,6 Figure 8 – Formula of polyester 6,6
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Characterization of Polymers
Salt preparation
Melt pre-polymerization
Solid-state polymerization
Thermal-Gravimetric Analysis (TGA)
Figure 10 – Perkin Elmer Pyris-1 Thermo-Gravimetric Analyzer
Fourier Transform Infrared Spectroscopy (FTIR)
Figure 12 – Nicolet Nexus 470 Spectrometer
Dilute Solution Viscosity
Figure 13 – Cannon-Ubbelhode Viscometer
pH
Figure 9 – pH meter
Differential Scanning Calorimetry (DSC)
Figure 11 – Perkin Elmer Diamond DSC-7 Instrument
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Characterization of Polymers
X-Ray Diffraction (XRD)
Figure 14 – Philips XLF, ATPS X-Ray Diffractometer
DSC
Co-polymerization
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FTIR Spectra
Figure 15 – FTIR spectra of nylon 6,6 and its components
* *Hexamethydiamine
0.1
0.2
0.3
Ab
s
* *Adipic A cid
0.2
0.4
Ab
s
* *Nylon 6,6 S alt
-0.0
0.1
0.2
Ab
s
* *Nylon 6-6
0.1
0.2
Ab
s
500 1000 1500 2000 2500 3000 3500 4000
Wavenumbers (cm-1)
Hexamethylenediamine
Adipic Acid
Nylon 6,6 Salt
Nylon 6,6
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Homopolymer Melting Scans
Figure 16 – DSC scans of homopolymer nylons
Nylon 6,6 melting point ΔH – 53 J/g Nylon 6,10 melting point ΔH – 76 J/g
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Intrinsic Viscosity and Molecular Weight
Intrinsic Viscosity ([η]) and Molecular Weights of Nylon 6,10 Pre-polymers
Initial production condition
[η] Molecular weight (g/mol)
Monomer mixture 0.125 dL/g 1,800
Fromsalts
Atmospheric pressure
0.266 dL/g 4,600
Elevated pressure 0.802 dL/g 19,000
Figure 17 – Intrinsic viscosity and molecular weight of nylon 6,10 pre-polymers
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Co-Polyamide Results
Figure 18– DSC scan of co-polyamide
Differences in Melting Points (Tms) and ΔHs of Tms vs Ratios of the Co-polyamides
Co-polyamide ratio (6,6 to 6,10)
Tm (°C) ΔH of melting points (J/g)
50% - 50% 192 3965% - 35% 220 41
80% - 20% 233 57
Figure 19– Tms and ΔHs of co-polyamide variations
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Conclusion
If two amorphous polymers, both with nearly identical inherent conformational flexibilities of their polymer chain backbones (factor 1) and no side chains (factor 2), differ in Tg, then this is caused by different interactions between polymer chains (factor 3).
• Inconclusive
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Future Directions
• Use of nylon mixture (co-polyamide)• Corresponding polyesters (co-polyester)
Figure 20 – DSC scan of 4 nylon mixture
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Acknowledgements
• God• Dr. Alan E. Tonelli, Alper Gurarslan, Jialong
Shen, Kathleen Dreifus• Friends and Family• NC Project SEED• Funders: The North Carolina Local Section of the
American Chemical Society, the Hamner Institute for Health Sciences, Biogen Idec, Greater Triangle Community Foundation, and the Burroughs-Wellcome Fund