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R P Thompson

The course covers the physical properties of polymers, including simple models for predicting behaviour and their origin in terms of molecular structure. The relationship between chemical structure, chain conformation, crystal structure and macroscopic properties is emphasised.

We first review the concept of polymer conformation, and how this can be described using the basic random walk model, before developing more sophisticated models that take into account correlations in segmental orientation. We will then focus on mechanical analogies (spring/dashpot models and linear elastic solid) for viscoelastic behaviour of glassy polymers. The crystallisation process of some polymers is then reviewed, before concluding with methods for enhancing strength and stiffness of polymer fibres by increasing orientation and alignment of their constituent molecules.

This lecture course will cover:

  • Molecular Tour of Common Polymer Types
  • Basic Concepts in Polymer Physics: The random walk model revisited, Kuhn chain, characteristic ratio, radius of gyration.
  • Non-crystalline Polymers: (a) Physical States of Polymers. Glass, melt, rubber and viscoelastic states, revision of glass transition.
  • Non-crystalline Polymers: (b) Mechanical Models for Polymers. Spring and dashpot mechanical analogue, Maxwell and Voigt elements, relaxation times and constitutive equations. Standard linear solid model, and relaxation time spectra.
  • Non-crystalline Polymers: (c) Polymer Physics of Deformation. Modulus of polymer glasses, properties in the region of Tg, time-temperature superposition, WLF equation and free volume justification. Revision of simple rubber elasticity. Viscosity, reptation, equations for characteristic time and viscosity, comparison with experiment, and entanglement molecular weight.
  • Crystallisation and Crystal Structure of Polymers: Factors preventing crystallisation, revision of tacticity and copolymers. Crystallisation mechanism, chain-folded morphology, thermodynamics, kinetic influence on crystal shape, entanglements and secondary crystallisation. Bulk kinetics and Avrami equation. Relationship between chemical structure, chain conformation and crystal structure for vinyl polymers, conformational diagrams and energy maps, effect of larger side groups and syndiotactic molecules. Polymer chain packing regimes.
  • Mechanical Properties of Solid Polymers: Yielding and plastic flow, drawing, and yield criteria (Tresca, von Mises). Fracture of glassy polymers, crazing. Rubber toughening of polymers. Reinforcement of rubbers.
  • High Performance Fibres: Theoretical values of strength and stiffness, textile fibres, super drawing, aligned solutions, gel drawing. Liquid crystalline polymers: thermotropic routes, Tm control through molecular design, lyotropic routes, processing, structure and properties of Kevlar and related polymer fibres. Carbon fibres and carbon nanotube fibres