LAUSR

Semiflexible polymer glasses (SPGs), including those formed by the recently synthesized semiflexible conjugated polymers, are expected to be brittle because classical formulas for their craze extension ratio λ_{craze} and fracture stretch λ_{frac} predict that systems with N_{e}=C_{∞} have λ_{craze}=λ_{frac}=1 and hence cannot be deformed to large strains. Using molecular dynamics simulations, we show that in fact such glasses can form stable crazes with λ_{craze}≃N_{e}^{1/4}≃C_{∞}^{1/4}, and that they fracture at λ_{frac}=(3N_{e}^{1/2}-2)^{1/2}≃(3C_{∞}^{1/2}-2)^{1/2}. We argue that the classical formulas for λ_{craze} and λ_{frac} fail to describe SPGs' mechanical response because they do not account for Kuhn segments' ability to stretch during deformation.