Compacted shape-memory polymer foams, which have the ability to achieve large expansions upon application of an external stimulus such as heat, are of great interest for minimally-invasive medical applications as (e.g. in surgery). While changing the composition of the polymer could only slightly improve the shape-memory properties of the foams, the major challenge remains to reach an almost complete recovery of the permanent shape. In this study we describe the pore morphology as structural parameter to alter shape-memory properties of polyetherurethane foams [1]. Thermally-induced phase separation was applied to create porous structures and adaption of the cooling protocol led to hierarchically structured bimodal or homogeneously distributed monomodal pore sizes. Quantification of the shape-memory effect was performed by cyclic, thermomechanical tensile tests and microscopic in situ shape-memory experiments. A hierarchically structured foam results on the microscale in bending of large pore walls during compression, while pore walls of homogeneous foams undergo buckling. Thesemicromechanical effects have substantial influence on the macroscopicshape-recovery rate Rr. Furthermore, the introduction of anisotropic pore morphologies leads to an anisotropic recovery enhanced in the longitudinal pore direction.References: [1] Sauter, T.; Luetzow, K.; Schossig, M.; Kosmella, H.; Weigel, T.; Kratz, K.; Lendlein, A. Adv. Eng. Mater. 2012  , 14, 818-824.

Pore morphology as structural parameter to tailor the shape-memory effect of polyuetherurethane foams

245th National Meeting (2013)

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