Probing the Bases of Polymer Glass Transitions

Miles Ndukwe

Millbrook High School

Raleigh, NC

Polymers

• Sustaining Life

• Dominating

Commerce

Figure 1 - DNA

Figure 2 – Rubber tire

Figure 3 - Plastics

Figure 4 - Clothing

Crystallinity

• Crystalline– Ordered

• Amorphous– Random

• Semi-crystalline– Consists of both

Figure 5 – Crystalline, amorphous, and semi-crystalline polymers

Crystalline

Amorphous

Semi-crystalline

Glass Transition Temperature (Tg)

• Hard, brittle Soft, rubbery

Figure 6 – Visual representation of polymers’ actions at Tg.

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

• 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

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.

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?

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.

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

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

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

Characterization of Polymers

X-Ray Diffraction (XRD)

Figure 14 – Philips XLF, ATPS X-Ray Diffractometer

DSC

Co-polymerization

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

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

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

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

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

Future Directions

• Use of nylon mixture (co-polyamide)• Corresponding polyesters (co-polyester)

Figure 20 – DSC scan of 4 nylon mixture

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