Shape memory polymers (SMPs) as smart materials have drawn increasing attention because of their specific capacity to recover from a tailored temporary shape to their original shape upon an external stimulus. Such an attractive ability endows SMPs with great potential to be extensively applied in actuators, intelligent packaging, biomedical devices and aerospace structures. In this work, a kind of SMPs containing alternating layers of thermoplastic polyurethane (TPU) and polycaprolactone (PCL) were fabricated through layer-multiplying co-extrusion technology. Compared with the conventional TPU/PCL blend, the multilayer structures with the same compositions showed better shape memory performance, which could be further promoted by increasing the number of layers. On the basis of a simple viscoelastic model, the strain energy stored in TPU layers could be balanced by adjacent PCL layers through interfacial shearing effect, thus that each component in the multilayer structure was able to endow the maximum contribution to both of the shape fixation and recovery. Subsequently, poly(butylene succinate) (PBS) as the second switching component was introduced into TCL layers forming PBS/PCL co-continuous blending layers (SLB) and multilayer-assembled with TPU layers. Based on the two well-separated melting transitions of PCL and PBS, the 128-layer TPU/SLB specimen with a multi-continuous structure and numerous interfaces presented an efficient triple-shape memory effect. Instead of incorporating more switching components, an alternate route to obtain multi-shape memory effect is achieving a broad thermal transition. Inspired by that, the miscible poly (vinylidene fluoride) (PVDF) and poly(methyl methacrylate) (PMMA) were co-extruded together forming 1024-layer specimens. The alternating multilayer distribution and the interfacial diffusion induced the formation of a broad glass transition range with a half-peak width of 63 <sup>o</sup>C and the quadruple-shape memory effect was realized at last. Accordingly, the fabrication of multilayer structure with high phase continuity and tunable interfacial effect might pave a new way for preparing outstanding SMPs.

Shape memory polymers with alternating multilayer structure

256th National Meeting (2018)

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