Quantifying the contributions of energy storage in a thermoset shape memory polymer with high stress recovery: A molecular dynamics study

Abstract

Molecular dynamics simulations were carried out to understand the mechanical and energy storage properties of bisphenyl-A diglycidyl ether cured with isophorone diamine — a thermoset shape memory polymer (TSMP) with both excellent shape memory and stress memory properties. Different cross-linked systems were created to determine which cross-linking percentage gave best agreement with experimental properties. It was found that for a 50% compression programming strain, higher cross-linking percentages stored more bond energy, but at the expense of a lower shape recovery. While bond energy was stored in the change in bond stretches, angles, and dihedrals, the bond angular and dihedral energies stored were significantly higher than bond stretches. Alkyl cyclic rings were able to store the most angular energy, but little to no stretching or dihedral energy, while non-ring polymer backbone atoms stored a significant amount of stretching, angular, and dihedral energies. Aromatic rings stored dihedral energy, but little angular energy. The results show that the type of functional group has a significant impact on how bond energy is stored, and could potentially be used to finely tune the shape recovery properties of TSMPs.