Study on the effect of transition temperature on shape memory behavior in polyurethane based on molecular dynamics simulation

The shape memory property of polyurethane is largely dependent on molecular self-aggregation and thermal-induced molecular diffusion. In this study, the molecule dynamic (MD) simulations were used to characterize the property of shape memory polyurethane (SMPU) from the atomistic scale. The transition temperature (T-trans) and self-aggregation were studied using the amorphous cell model. A three-layered model of SMPU was built intentionally to evaluate the thermal-induced diffusion of molecules. The results indicated that suitable molecule is beneficial for predicting the T-trans through free volume analysis. The Radius Distribution Function (RDF) of the amorphous cell model demonstrated strong self-aggregation behavior. In order to bring SMPU to the optimal self-recovery capacity, it was suggested to set the melting point of soft segment as the target temperature. At the melting point of soft segment, the whole molecule system reached the relatively stable state on the basis of cohesive energy densities.