This chapter describes the properties arising due to the defining feature of polymers—the enormous size of their constituent molecules. This size and the large aspect ratio of ‘macromolecules’ cause high elasticity and viscoelasticity. High elasticity refers to the ability of flexible-chain polymers to recover from large strains, a property unique to rubber. Viscoelasticity describes a time-varying reaction to a transient perturbation, unaccompanied by any change in the material; viscoelastic materials both dissipate and store energy during deformation. These two characteristics underlie most applications of rubbery materials. The chapter provides an overview of the molecular basis for the behavior, including the local and segmental motions, the chain dynamics, the effect of entanglements, and the application of fluctuation-dissipation theory.
Keywords: stress relaxation, viscoelasticity, relaxation time, local segmental dynamics, friction coefficient, Rouse model, reptation, modulus, time correlation function, fluctuation-dissipation theory
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