Structure and Mechanical Properties of a Porous Polymer Material via Molecular Dynamics Simulations

We characterize, using molecular dynamics simulations, the structure and mechanical response of a porous glassy system, obtained via arrested phase separation of a model polymer melt. In the absence of external driving, coarsening dynamics, with power-law time dependence, controls the slow structural evolution, in agreement with what was reported for other phase-separating systems. The mechanical response was investigated in athermal quasi-static conditions. In the elastic regime, low values for the Young's and shear modulus were found, as compared to dense glassy systems, which originate from the porous structure. For large deformations, stress-strain curves show a highly intermittent behavior, with avalanches of plastic events. The stress-drop distribution is characterized exploring a large set of parameters. This work goes beyond the previous numerical studies on atomic porous materials, as it first examines the role of chain connectivity in the elastic and plastic responses of materials of this type.