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Abstract

Shape memory materials find a large variety of applications ranging from solar panels and wind foils to stents, the latter used to widen sclerotic coronary arteries. Among these, metallic shape memory alloys (SMAs) are often used as mechanical switches, whereas shape memory polymers (SMPs) show promising biocompatibility potentials and therefore find increasing applications in biomedicine. Common to all these materials is their ability to recover a programmed shape via activation of a switching mechanism, e.g., heating above a certain threshold temperature. The recovery process in SMAs is a diffusionless martensitic phase transformation. The shape memory effect in polymers, on the other hand, has an entropic origin: Upon heating above the glass transition temperature, stretched polymers, which had been immobilized via cooling to room temperature, become mobile again and recover a high entropic spherical conformation. This presentation provides a brief survey of these fascinating materials and their applications. It also addresses the effect of small solvent molecules on the shape recovery process in SMPs both from the experimental side and via molecular dynamics computer simulations of simple model systems.

References:
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[3] E. M. Zirdehi, H. Dumlu, G. Eggeler, F. Varnik, On the Size Effect of Additives in Amorphous Shape Memory Polymers, Materials 14, 327 (2021).