Shape-Memory Properties of Polyetherurethane Foams Prepared by Thermally Induced Phase Separation

In this study, we report the preparation of two structurally different shape‐memory polymer foams by thermally induced phase separation (TIPS) from amorphous polyetherurethanes. Foams with either a homogeneous, monomodal, or with a hierarchically structured, bimodal, pore size distribution are obtained by adoption of the cooling protocol. The shape‐memory properties have been investigated for both foam structures by cyclic, thermomechanical experiments, while the morphological changes on the micro scale (pore level) have been compared to the macro scale by an in situ micro compression device experiment. The results show that the hierarchically structured foam achieves higher shape‐recovery rates and a higher total recovery as compared to the homogeneous foam, which is due to an increased energy storage capability by micro scale bending of the hierarchically structured foam compared to pure compression of the homogeneous foam. The structure of foams prepared from amorphous polyetherurethane via thermally induced phase separation could be adjusted by application of different cooling protocols. Shape‐memory investigations on the macro‐ and microscale revealed an improved shape‐memory capability for hierarchically structured foams (PEUfc), which can be attributed to an increased energy storage capability compared to foams with homogeneous pore size distribution (PEUsc).