Programmable and sophisticated shape-memory behavior via tailoring spatial distribution of polymer crosslinks

Abstract

Increasing the spatial localization of material response is crucial for increasing the behavioral complexity of shape-memory polymer (SMP) actuators, which is strongly dependent on the spatial distribution of networks in SMP. An interesting approach is proposed in this study. We used diol crosslinkers with different fatty chain lengths to construct networks in biomass-derived poly(L-malic acid) (PMA) and thus obtained SMPs with different network geometries. The crosslinking followed a two-step route: esterification for pre-crosslinks, and further curing to obtain the target sample. Combining different pre-cross-linked pieces, followed by curing then, is an effective method for programming the spatial distribution of crosslinks and providing behavioral complexity to bulk SMP. Besides, using the as-obtained SMP bulk as the compound ‘joint’, multi-material systems with step-by-step responding capacities could be fabricated to better complete a series of sophisticated and asynchronous movements. This work enriches the approaches of combining polymer architecture and macroscale processing to improve programmable recovery and actuation in SMPs.