Pore-size distribution controls shape-memory properties on the macro- and microscale of polymeric foams

摘要

Open porous foams with identical foam density but different pore-size distributions (bimodal or monomodal) are prepared from a shape-memory polyetherurethane (PEU) by thermally induced phase separation. The shape-memory effect of the two PEU foams is explored by cyclic thermomechanical compression tests and microstructural analysis. The obtained results reveal that the PEU foam with a bimodal pore-size distribution exhibits an increased shape-recovery under stress-free conditions, both on the macro- (foam level) as well as the microscale (pore level). While bimodal pore-size distributions induce microscale bending during compression, buckling occurs in foams with monomodal pore-size distributions, leading to both a reduced and delayed shape recovery. The shape-memory effect of polymer foams is influenced by their morphology and density. Two shape-memory polymer foams are prepared by thermally induced phase separation with identical foam density but different pore-size distributions. While bimodal pore-size distributions induce microscale bending during compression, buckling occurs in foams with a monomodal pore-size distribution, leading to both a reduced and delayed shape recovery.