Small additive molecules often enhance structural relaxation in polymers. We explore this effect in a thermoplastic shape memory polymer via molecular dynamics simulations. The additive-to-monomer size ratio is shown to play a key role here. While the effect of additive-concentration on the rate of shape recovery is found to be monotonic in the investigated range, a non-monotonic dependence on the size-ratio emerges at temperatures close to the glass transition. This work thus identifies the additives' size to be a qualitatively novel parameter for controlling the recovery process in polymer-based shape memory materials.
Keywords: molecular dynamics simulations; shape memory polymers; size effect of additives.