A microscopic view of the response of disordered polymer solids to deformation

Disordered polymers with solid properties come in a variety of shapes and sizes, from amorphous polymer glasses to porous membranes to cross-linked polymer networks. While homogeneous on large length scales, on the molecular scale the mechanical response is known to be strongly inhomogeneous. That is, upon deformation, some regions deform more than others and can even rupture before others. In this talk, I will describe two vignettes from my group's work to understand how inhomogeneous polymer solids response to deformation. In polymer glasses under shear stress, it is commonly observed that the dynamics become more homogeneous under load, and the distribution of relaxation times narrows. We use a machine learning approach to show how the energy barriers of the slower regions respond more strongly to stress and as a result have their energy barriers reduced more than the faster domains. In cross-linked polymer networks, there has been some recent debate about the amount of energy that is dissipated when strained to the point of chain scission. We have performed a series of simulations using model polymers with breakable bonds and calculated the energy dissipated as a function of the polymer chain length and volume fraction, providing new clues on the energy required to fracture a polymer gel.