Ban Jianfeng,Yang Zilong,Pan Lulu,Liao Junqiu,Shi Bo
This work was designed to investigate the complex shape memory phenomena and explore the potential for bidirectional reversibility within polymer matrices, focusing particularly on dual-response capabilities. A series of shape memory azobenzene liquid crystal elastomers (Dp-LCEs) were synthesized with azobenzene-4,4'-dicarboxylic acid, polycaprolactone, and hexamethylene diisocyanate as the primary raw materials, and triethanolamine was utilized to establish cross-linking points. The structural and thermal properties of these Dp-LCEs were meticulously characterized through Fourier-transform infrared spectroscopy, thermogravimetric analysis, differential scanning calorimetry, and X-ray diffraction techniques. According to the structural and thermal properties test results, they afforded a deep understanding of the material's composition and thermal behavior, essential for optimizing its performance in practical applications. Furthermore, the stretchability, photo-thermal responsiveness, and reversible deformation capabilities of the Dp-LCEs were assessed via stretching tests and by subjecting them to ultraviolet radiation. The findings revealed that the Dp-LCEs demonstrated distinctive photo-thermo-synergy response shape memory features and exhibited outstanding bidirectional reversible shape memory behavior. This research work provided a solid theoretical basis for customization of the advanced multifunctional shape memory materials, potentially paving the way for innovative applications in various fields such as smart textiles, biomedical devices, and adaptive structures. These advancements suggested significant potential for future developments in smart material technologies, particularly in areas requiring precise environmental responsiveness and high-performance adaptability. Graphical
Two-way reversible shape memory polymers (2W-SMPs), capable of changing their shape reversibly, are highly desirable for many potential applications. However, the polymerization reactions used for preparing 2W-SMPs always require harsh conditions, such as metal catalysts, light irradiation and elevated temperature. Furthermore, there are few reports on SMPs that integrated with other functions, such as luminescence. Herein, luminescent 2W-SMPs of semi-crystalline PCL-based networks bearing an aggregation-induced emission (AIE) moiety of tetraphenylethylene (TPE) are designed and prepared via an organobase-catalyzed hydroxyl–yne click polymerization under mild reaction conditions. For comparison, a TPE-free polymer network is also prepared through the same polymerization. The TPE-containing polymer network shows stronger emission than that of the TPE-containing monomer because of the restriction of intramolecular rotation. Both the polymer networks are able to perform excellent reversible shape motions, such as bending–unbending, coiling–uncoiling, and closing–blooming, when they are exposed to cold and warm water. By taking advantage of the shape memory and luminescence properties, the TPE-containing polymer network could be used to construct a luminescent robotic gripper, which can grab and release weights with payload-to-weight ratios much higher than that of many industrial robotic grippers. Moreover, it could also be used to realize a double anti-counterfeiting function. This work represents the first example of luminescent 2W-SMPs, which might be widely applied in diverse areas.
In this work, a simple method is proposed for the preparation of bidirectionally reversible light-responsive shape memory polyurethane (SMPU) bilayer. This SMPU bilayer consists of a 4,4-azodibenzoic acid (Azoa) containing SMPU (SMPU-Azoa) layer and a carbon black (CB) containing SMPU (SMPU-CB) layer. A reversible deformation is realized when the two sides are exposed to ultraviolet (UV) and infrared (IR) lights, respectively. The working mechanism is the trans – cis isomerization of SMPU-Azoa layer and the photo-thermal effect of SMPU-CB layer. The effect of the filler content and the thickness ratio of bilayer is systematically studied. The reversible bending angle of the SMPU bilayer can exceed 30° in 16 s for one cycle when the Azoa and CB contents are 5 wt% and 0.5 wt%, respectively, and the thickness ratio of SMPU-Azoa layer to SMPU-CB layer is 1/1.3. Furthermore, a micro-robot based on such LSMP bilayer is demonstrated.
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