Molecular dynamics simulations of the shape-memory behaviour of polyisoprene

Full-atomistic molecular dynamics simulations are used to study the shape-memory behaviour of a representative amorphous polymer. A virtual polyisoprene was constructed and subjected to uniaxial stretch and hydrostatic compression thermomechanical cycles. Uniaxial stretch loading results demonstrate that a temporary shape can be stored at low temperature and that the original shape can be recovered at high temperature due to the entropy effect involved in a change of shape at high temperature. The material volume change during pure hydrostatic loading resulted in a change of internal energy. The volume change could not be stored at low temperature without applying hydrostatic stresses. These results shed light on the fundamental mechanisms driving shape memory and recovery in amorphous polymers.