Coarse-grained molecular dynamics study of elasticity of block copolymers with cubic symmetrical morphology

In the present study, we investigated the elasticity of block copolymers by coarse-grained molecular dynamics simulation. We focused on two typical cubic symmetry morphologies that mimic thermoplastic elastomers and soft plastics-i.e., body-centered cubic (BCC) and double gyroid (DG). The effects of morphology, bridge fraction, and deformation direction on the stress-strain curves were studied. The deformation of glassy networks with the DG morphology resulted in higher initial moduli than those with the BCC morphology. With the BCC morphology, the rubber elasticity was linearly dependent on the bridge fraction, whereas with the DG morphology the dependency was weak because the loop configuration in the DG networks also contributed to rubber elasticity. In both the BCC and DG morphologies, the effect of deformation direction was insignificant. This was inconsistent with the experimental results. The discrepancy demonstrates the peculiar nature of the coarse-grained bead-spring model in the glassy state.

Automated summary

This study investigated the elasticity of block copolymers through coarse-grained molecular dynamics simulation. The effects of morphology, bridge fraction, and deformation direction on stress-strain curves were studied. The results showed that glassy networks with the DG morphology had higher initial moduli compared to those with the BCC morphology. The rubber elasticity was linearly dependent on the bridge fraction in BCC morphology, but weakly dependent in DG morphology due to the contribution of loop configurations. The effect of deformation direction was insignificant in both morphologies, contrary to experimental results.