Manipulating the chain network in glassy polymers to alter its mechanical responses*

We study a simplest mechanical network, a glassy polymer, in terms of its nonlinear mechanical responses. Like all other networks, the key mechanics questions are how deformable is the network, what determines the mechanical strength, how the system undergoes structural failure. Some glassy polymers are ductile well below their glass transition temperatures, some are incapable of yielding and suffer brittle fracture. Polystyrene is brittle in tensile extension but ductile in compression at room temperature. Is polystyrene always ductile in compression? Our presentation discusses the latest experiments inspired by a recent molecular model¹ for mechanics of glassy polymers.
1. S. Q. Wang, S. W. Cheng, P. P. Lin and X. X. Li, "A phenomenological molecular model for brittle-ductile transition and yielding of polymer glasses", J. Chem. Phys. 141, 094905 (2014).