Solvent-driven temperature memory and multiple shape memory effects.

Thermally-activated temperature memory and multiple shape memory effects have been observed in amorphous polymers with a broad glass transition. In this work, we demonstrate that the same shape recovery behaviors can also be achieved through solvent absorption. We investigate the recovery behaviors of programmed Nafion membranes in various solvents and compare the solvent-driven and temperature-driven shape recovery response. The results show that the programming temperature and solvent type have a corresponding strong influence on the shape recovery behavior. Specifically, lower programming temperatures induce faster initial recovery rates and larger recovery, which is known as the temperature memory effect. The temperature memory effect can be used to achieve multi-staged and multiple shape recovery of specimens programmed at different temperatures. Different solvents can also induce different shape recovery, analogous to the temperature memory effect, and can also provide a mechanism for multi-staged and multiple shape memory recovery.