冷冻/解冻聚乙烯醇水凝胶：现在、过去和未来,European Polymer Journal

介绍了通过冷冻/解冻 (FT) 工艺制备的聚乙烯醇 (PVA) 水凝胶的综合综述。我们讨论了它们的制备、凝胶机制、物理/机械性能的处理、物理化学特性和各种应用。由于 PVA 溶液的分子结构和结晶能力，在没有外部添加交联剂的情况下通过重复 FT 发生 PVA 凝胶化，从而产生超纯水凝胶。凝胶化因素，如 FT 循环数、使用的最高和最低温度、循环持续时间，以及所用 PVA 样品的分子特征，如平均分子量和水解程度，能够精确调整结晶、氢键以及最终的水凝胶特性。掺入第二聚合物和/或纳米颗粒，这分别导致互穿的聚合物网络和纳米复合材料，进一步有助于获得理想的最终性能，从而为各种应用定制凝胶。PVA 的特性易于定制以及生物相容性导致了各种假体材料的开发，包括血管支架、软骨，甚至隐形眼镜。此外，PVA 水凝胶也一直在研究用于药物输送载体和伤口敷料。此外，PVA 水凝胶可能具有多种其他有趣的特性，例如自主自愈能力和程序形状记忆特性。因此，PVA 水凝胶可用作致动器中的组件。还讨论了 FT PVA 水凝胶在离子导电和光子晶体传感器中的应用。

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A comprehensive review of polyvinyl alcohol (PVA) hydrogels prepared by the freezing/thawing (F-T) process is presented. We discuss their preparation, gelation mechanisms, handling of physical/mechanical properties, physicochemical characteristics, and various applications. PVA gelation through repeated F-T occurs without an externally added crosslinking agent due to the molecular structure and ability of PVA solutions to crystallize, resulting in ultrapure hydrogels. Gelation factors such as F-T cycle number, maximum and minimum temperature used, cycle duration, as well as molecular characteristics of the employed PVA samples, such as the average molecular weight, and the degree of hydrolysis, enable precise tuning of crystallization, hydrogen bonding as well as the final hydrogel properties. Incorporation of a second polymer and/or nanoparticles, which respectively results in interpenetrating polymer networks and nanocomposites, further facilitates obtaining desirable final properties to customize the gels for variety of applications. Facile customizability of the properties along with biocompatibility of PVA has led to the development of diverse prosthetic materials ranging from vascular stents, cartilages, and even contact lenses. In addition, PVA hydrogels have also been under investigation for drug delivery vehicles, and wound dressings. Furthermore, PVA hydrogels may possess a variety of other interesting features such as autonomous self-healing ability and programmed shape memory characteristic. As such PVA hydrogels can be used as components in actuators. Applications of the F-T PVA hydrogels in ionically conductive- and photonic crystal-based sensors are also discussed.