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 1 H 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 (T m,PTMEG and T g,PDLLA ), which can be utilized as T 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.

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Polymers with two-way shape memory effect (2W-SME) are of great potential in real applications due to the reversible nature. Though 2W-SME has been already realized in some semicrystalline networks by the crystallization-induced elongation (CIE) and melting-induced contraction (MIC), more adaptable 2W-SME systems are highly expected. In this work, to achieve tunable 2W-SME with different reversible deformation ranges, we designed a semicrystalline poly-(tetramethylene oxide) glycol (PTMEG) network with temperature-switched netpoints. This adaptable network was constructed by photo-cross-linking of the PTMEG-based copolymer containing amorphous poly(D,L-lactide) (PDLLA) segments in main chain and photosensitive anthracene groups in side chain. The photo-cross-linking degrees of networks were adjusted by controlling irradiation time. Remarkably, 2W-SME in the current system was realized by the CIE and MIC of PTMEG segments for the first time. Here, along with the photo-cross-links, the low content of PDLLA served as a switchable netpoint which was controlled by high temperature (T high ). Differential scanning calorimetry (DSC) analysis revealed that all the photo-cross-linked networks exhibited desirable crystallinity. Dynamic mechanical analysis (DMA) indicated that there were two distinct declines of storage modulus (E′) when temperature crossed T m,PTMEG and T g,PDLLA , which guided us to choose 45 and 70 °C as two specific T high s. 2W-SME was investigated by DMA under constant stress; in detail, the effects of applied stress, T high , and photo-cross-linking degree synergizing with the switchable netpoints structure on the characteristics of 2W-SME (ε i , ε Non-CIE , ε CIE , R act (σ), and R rec (σ)) have been disclosed.