New Strategy to Access Dual-Stimuli-Responsive Triple-Shape-Memory Effect in a Non-overlapping Pattern.

Multistimuli-responsive shape-memory polymers are highly desirable in various applications, and numerous modes have been developed in recent years. However, most of them need to reprogram before they are ready to respond to another stimulus while one is triggered. Here, a new strategy is developed to achieve dual-stimuli-responsive triple-shape memory with non-overlapping effect in one programming cycle. Here, a series of poly(l-lactide)-poly(tetramethylene oxide) glycol copolymers (PLA-PTMEG-A) is prepared by selected dangling photoresponsive anthracene moieties on the crystalline PTMEG backbone. The architectures of the copolymers are well-controlled in order to keep a good balance between the crystallinity of the soft segment and the mobility of the anthracene moieties. Thus, PLA-PTMEG-A's can respond to heat and light with non-overlapping effect. The thermally-induced shape-memory effect (TSME) is realized by the crystallization-melting transition of PTMEG soft segments, while the light-induced shape-memory effect (LSME) is achieved by the reversible photodimerization of anthracene groups. In view of the non-overlapping effect of TSME and LSME in the copolymers, a triple-shape-memory effect triggered by dual-stimuli is realized in one programming and recovery cycle.