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形状记忆聚合物(SMPs)是近些年发展起来的一种环境响应型智能材料。在外界刺激驱动下分子内或分子间会发生物化变化,分子结构和形态的改变使形变后的材料在宏观上回复到起始形态。常见的SMPs有聚乙烯、聚氨酯、聚己内酯等,而聚乙烯醇(PVA)的形状记忆效应是在热致型形状记忆凝胶被发现以来才引起人们关注的。由于PVA侧链富含大量羟基,化学活性高、易与官能团进行功能化改性,因此可设计出满足不同驱动方式的分子结构。目前研究者已采用冻融循环、化学或辐射交联、接枝改性及共混复合等多种方法制备了多种刺激源(如温度,溶剂、光、电、微波及超声波等)驱动下的形状记忆聚乙烯醇(SM-PVA)、PVA衍生物及复合材料。本文综述了近年来不同刺激源驱动下SM-PVA的研究进展,阐述了不同材料的结构性能、回复机理及存在的问题,并展望了PVA在该领域的发展和应用前景。
Shape memory polymers (SMPs) have developed in recent years as an environment-responsive smart material. Driven by external stimuli, intramolecular or intermolecular changes of the material will occur, the molecular structure and morphological changes in the deformed material to macroscopically back to the initial morphology. Common SMPs are polyethylene, polyurethane, polycaprolactone, etc. However, the shape memory effect of polyvinyl alcohol (PVA) has drawn attention since the discovery of thermosensitive shape memory gels. PVA side chain is rich in a large number of hydroxyl groups, high chemical activity, easy functionalization with functional groups, it can be designed to meet the different molecular structure of the drive. At present, researchers have prepared a variety of stimuli (such as temperature, solvent, light, electricity, microwave and ultrasound) driven by freeze-thaw cycles, chemical or radiation crosslinking, graft modification and blending compounds Of shape memory polyvinyl alcohol (PVA), PVA derivatives and composites. In this paper, the research progress of SM-PVA driven by different stimuli in recent years is reviewed. The structural properties, recovery mechanisms and existing problems of different materials are expounded. The development and application prospects of PVA in this field are also prospected.