Why is Understanding Glassy Polymer Mechanics So Difficult?

Abstract

In this Perspective, I describe recent work on systems in which the traditional distinctions between (i) unentangled vs. well-entangled systems and (ii) melts vs. glasses seem least useful, and argue for the broader use in glassy polymer mechanics of two more dichotomies: systems which possess (iii) unary vs. binary and (iv) cooperative vs. nonccoperative relaxation dynamics. I discuss the applicability of (iii-iv) to understanding the functional form of glassy strain hardening. Results from molecular dynamics simulations show that the "dramatic" strain hardening observed in densely entangled systems is associated with a crossover from unary, noncooperative to binary, cooperative relaxation as strain increases; chains stretch between entanglement points, altering the character of local plasticity. Promising approaches for future research along these lines are discussed.

Results and conclusions same but manuscript extensively edited for clarity. Accepted for publication in J. Polym. Sci. - Polym. Phys

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Cited by in corpus (4)

• Measurement of segmental mobility during constant strain rate deformation of a poly(methyl methacrylate) glass
• Nonmonotonic dependence of polymer glass mechanical response on chain bending stiffness
• Multiscale equilibration of highly entangled isotropic model polymer melts
• Relaxation time of a polymer glass stretched at very large strains