Structural design of polyurethane/poly(butylene succinate)/polycaprolactone compounds via a multilayer-assembled strategy: achieving tunable triple-shape memory performances.

Shape memory polymeric materials composed of thermoplastic polyurethane (TPU), poly(butylene succinate) (PBS), and polycaprolactone (PCL) were prepared through layer-multiplying co-extrusion of blends. With the two well-separated melting transitions respectively from PCL and PBS, the multicomponent compounds realized triple-shape memory effect. By tailoring the structure of the individual layer, the multilayer systems with designable phase morphology were fabricated, which developed tunable shape memory performances. Particularly, the multi-continuous structure containing alternating layers of TPU and the co-continuous PBS/PCL blend presented the optimal shape fixity and recovery ratios, whose minimum value can reach 84%. It was revealed that the high phase continuity along the deformation direction and the strong interfacial shearing effect promoted the ability to fix the temporary shapes and recover them to the permanent state. In addition, the multi-continuous structure maximized the synergy of the components in mechanical properties, resulting in an excellent balance of tensile strength and ductility. The present strategy for morphology control of multicomponent structures provides a promising method to fabricate outstanding triple-shape memory polymers with optimal mechanical properties.