A Facile Strategy To Construct PDLLA-PTMEG Network with Triple-Shape Effect via Photo-Cross-Linking of Anthracene Groups

Covalently cross-linked network has been widely applied in triple-shape memory polymers (TSPs), and fabricating triple-shape memory networks with the optional shapes through a facile and fast way is highly expected in the real applications. In this study, a “preshaped and post-cross-linking” strategy has been put forward to fabricate the triple-shape networks via fast photo-cross-linking in solid state. The photoresponsive anthracene group was first employed to develop a poly­(d,l-lactide)–poly­(tetramethylene oxide) glycol (PDLLA-PTMEG) network via UV light irradiation. Two steps were involved in network fabrication: first, linear copolymers (AN-PDLLA-PTMEG) containing anthracene groups on the side chains with different mass ratio of PDLLA segments were synthesized, and then PDLLA-PTMEG networks (NW-PDLLA-PTMEG) were formed by 365 nm UV light irradiation under an argon atmosphere. The structures of all the precursors were determined by ¹H NMR, and all networks were evaluated by swelling tests. The results of tensile tests show that the content of PDLLA segments has a crucial effect on the mechanical performance of the materials. Differential scanning calorimetry (DSC) analysis combined with dynamic mechanical analysis (DMA) reveals that all the NW-PDLLA-PTMEG’s display two thermal transitions (<i>T</i>_m,PTMEG and <i>T</i>_g,PDLLA), which can be utilized as <i>T</i>_trans to trigger triple-shape memory behavior. The cyclic thermal mechanical testing for triple-shape effects of NW-PDLLA-PTMEG, which was performed by DMA, demonstrates that the mass ratio of two segments has a great effect on the shape fixity and shape recovery. Moreover, a practical application as heat-shrinkable tube (or film) has been put forward