Title: Nonmonotonic dependence of polymer glass mechanical response on chain bending stiffness,
Abstract: We investigate the mechanical properties of amorphous polymers by means of
coarse-grained simulations and nonaffine lattice dynamics theory. A small
increase of polymer chain bending stiffness leads first to softening of the
material, while hardening happens only upon further strengthening of the
backbones. This nonmonotonic variation of the storage modulus $G'$ with bending
stiffness is caused by a competition between additional resistance to
deformation offered by stiffer backbones and decreased density of the material
due to a necessary decrease in monomer-monomer coordination. This
counter-intuitive finding suggests that the strength of polymer glasses may in
some circumstances be enhanced by softening the bending of constituent chains.