Understanding the mechanical behavior
of glassy polymers at a fundamental molecular level is of critical
importance in engineering and technological applications. Among various
molecular parameters, cohesive interactions between polymer chains
are found to play a key role in influencing the thermomechanical response
of glass-forming polymers. Here, we employ atomistically informed
coarse-grained molecular dynamics (CG-MD) simulations to study the
mechanical properties of the polymer material in a glassy state. Built
upon the recently developed “energy renormalization”
(ER) coarse-graining approach, we take polycarbonate (PC) as a model
system to systematically explore the shear response and dynamical
heterogeneity of polymers under the influence of cohesive interactions.
Our results show that the polymer with a larger cohesive interaction
exhibits a greater shear modulus and a higher degree of dynamical
heterogeneity, which is uncovered by evaluating the local molecular
stiffness. This pronounced dynamical heterogeneity with increasing
cohesive interactions is found to be closely correlated to the packing
frustration at a molecular level, which can be quantified by the glass “fragility”,
a measure of the relative strength of the temperature dependence of
relaxation. Our findings highlight the critical role of cohesive interaction
on the mechanical behavior of glassy polymers and provoke the idea
of achieving a tailored design of polymer materials via molecular-level
engineering.