A novel light-induced shape-memory material based on poly(l-lactide)-poly(ethylene glycol) copolymer is developed successfully by dangling the photoresponsive anthracene group on the PEG soft segment selectively. For synthesis strategy, the preprepared photoresponsive monomer N,N-bis(2-hydroxyethyl)-9-anthracene-methanamine (BHEAA) is first embedded into PEG chains; then, we couple this anthracene-functionalized PEG precursor with PLA precursor to result in PLA-PEG-A copolymer. The composition of target product can be well-defined by simply adjusting the feed ratio. The chemical structures of intermediate and final products are confirmed by (1)H NMR. Differential scanning calorimetry analysis of material reveals that the PEG soft segment became noncrystallizable when 4% or more BHEAA is introduced, and this feature is beneficial to the mobility of anthracene groups in polymer matrix. The static tensile tests show that the samples exhibit rubberlike mechanical properties except for the PLA-dominant one. The reversibility of [4 + 4] cycloaddition reaction between pendant anthracene groups in PLA-PEG-A film is demonstrated by UV-vis. Eventually, the light-induced shape-memory effect (LSME) is successfully realized in PLA-PEG-A. The results of cyclic photomechanical tests also reveal that the content of PLA hard segment as well as photosensitive anthracene moieties plays a crucial role in LSME.

Two-way shape-memory polymers (2W-SMPs) show great potential in actuating applications such as robotics due to their reversibility; indeed, multiresponsive 2W-SMPs are more expected. Inspired by the fascinating adhesion effects of mussels, we herein describe a metallo-supramolecular poly­(ε-caprolactone) (PCL)-based network constructed around catechol chemistry, leading to excellent thermal/magnetic/light-responsive two-way shape-memory effects (2W-SME) as well as self-healing capacity. These hybrid networks get readily self-assembled upon metal coordination interaction between superparamagnetic iron oxide nanoparticles (Fe3O4 NPs) and catechol-telechelic PCL. The incorporation of Fe3O4 NPs may act as the strong netpoints which allow the networks with excellent thermal-responsive one-way (1W) and 2W-SME, due to the ability of the semicrystalline PCL segments to present both crystallization-induced elongation (CIE) and melting-induced contraction (MIC) under constant stress. As a multifunctional medium, moreover, it also endows the hybrids with the magnetic-responsive 2W-SME in an alternating magnetic field and the light-induced SME triggered by the near-infrared light. Thanks to the dynamic nature of this metal coordination interaction inspired by mussel, the target hybrid networks also showed good self-healing capability. A model of magnetic-triggered actuator was well-established, which allows to the material with interesting applications such as remote-control or intelligent magnetic-sensitive devices.

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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