Coarse-Grained Molecular Dynamics Simulation of Polycarbonate Deformation: Dependence of Mechanical Performance by the Effect of Spatial Distribution and Topological Constraints

Polycarbonate is an engineering plastic used in a wide range of applications due to its excellent mechanical properties, which are closely related to its molecular structure. We performed coarse-grained molecular dynamics (CGMD) calculations to investigate the effects of topological constraints and spatial distribution on the mechanical performance of a certain range of molecular weights. The topological constraints and spatial distribution are quantified as the number of entanglements per molecule (Ne) and the radius of gyration (R-g), respectively. We successfully modeled molecular structures with a systematic variation of N-e and R-g by controlling two simulation parameters: the temperature profile and Kuhn segment length, respectively. We investigated the effect of Ne and R-g on stress-strain curves in uniaxial tension with fixed transverse strain. The result shows that the structure with a higher radius of gyration or number of entanglements has a higher maximum stress (sigma m), which is mainly due to a firmly formed entanglement network. Such a configuration minimizes the critical strain (epsilon c). The constitutive relationships between the mechanical properties (sigma m and epsilon c) and the initial molecular structure parameters (Ne and Rg) are suggested.