Beijing Key Laboratory of Energy Conversion and Storage Materials, College of Chemistry , Beijing Normal University , Beijing 100875 , P. R. China.
ACS Appl Mater Interfaces. 2018 Sep 26;10(38):32707-32716. doi: 10.1021/acsami.8b11391. Epub 2018 Sep 12.
Shape memory hydrogels (SMHs) have a wide range of potential practical applications. However, the mechanically weak and soft nature of most SMHs strongly impedes their applications. Here, we report a novel kind of thermal-responsive SMH with high tensile strength and high elastic moduli. Organogels are first prepared by the copolymerization of a hydrophilic monomer N-vinylpyrrolidone (NVP) and a hydrophobic monomer acryloxy acetophenone (AAP) in N, N'-dimethylformamide (DMF) solutions, and then, poly(vinylpyrrolidone- co-acryloxy acetophenone) [poly(NVP- co-AAP)] hydrogels are obtained by solvent exchange with water. Because of the strong and reversible hydrophobic association and π-π stacking of acetophenone groups, the poly(NVP- co-AAP) hydrogels exhibit tensile strengths up to 8.41 ± 0.83 MPa and Young's moduli up to 94.2 ± 1.3 MPa, which are more than 1 or 3 orders of magnitude higher than those of the organogels, respectively. The poly(NVP- co-AAP) hydrogels exhibit good shape memory behaviors, with a complete fixation ratio and a recovery ratio of 74-89%, as well as very fast shape-fixing and recovering rates (in seconds). These rigid and strong hydrogels are demonstrated to be an ideal shape memory material for surgical fixation devices to wrap around and support various shapes of limbs.
形状记忆水凝胶（SMHs）具有广泛的潜在实际应用。然而，大多数 SMHs 的机械强度弱且柔软的性质严重阻碍了它们的应用。在这里，我们报告了一种新型的热响应 SMH，具有高拉伸强度和高弹性模量。首先在 N, N'-二甲基甲酰胺（DMF）溶液中通过亲水单体 N-乙烯基吡咯烷酮（NVP）和疏水性单体丙烯酰氧基苯乙酮（AAP）的共聚反应制备有机凝胶，然后通过溶剂交换用水得到聚（乙烯基吡咯烷酮-co-丙烯酰氧基苯乙酮）[聚（NVP-co-AAP）]水凝胶。由于苯乙酮基团的强烈和可逆的疏水缔合和π-π堆积，聚（NVP-co-AAP）水凝胶表现出高达 8.41 ± 0.83 MPa 的拉伸强度和高达 94.2 ± 1.3 MPa 的杨氏模量，分别比有机凝胶高 1 或 3 个数量级以上。聚（NVP-co-AAP）水凝胶表现出良好的形状记忆行为，具有 74-89%的完全固定率和恢复率，以及非常快速的形状固定和恢复速率（在几秒钟内）。这些刚性和高强度的水凝胶被证明是一种理想的形状记忆材料，用于手术固定装置，以包裹和支撑各种形状的四肢。
