形状记忆聚合物的三维塑性变形调控研究

Shape memory polymers (SMPs) possess the ability to controllably change their external shapes under stimuli. They are well studied in recent years, while their three-dimensional (3D) shapes are still hardly to be obtained at room temperature, and the shape-changing behaviors are relatively simple. On another aspect, some polymers can change their shapes by plastic deformation through forced orientation or strain-induced crystallization of polymer chains. Based on these facts, we propose a novel strategy of "tuning constrained plastic deformation via reversible crosslinking" to realize 3D shape change of SMPs at room temperature. The material was constructed using polyethylene oxide and carboxyl containing-polymers, and gradient crosslinking of Fe(III)-carboxyl coordination were introduced at desired areas after surface patterning. Under stretch, constrained plastic deformation would happen at these areas, resulting in bending and 3D shape change of the material. Furthermore, by controlling reversible construction of Fe(III)-carboxyl coordination in different areas under visible light-reduction and air-oxidation, 3D shape of the material can be tuned by external stimuli and exerted force. To realize this strategy, the relationship between composition and properties, conditions of surface patterning, reversible formation of gradient crosslinking, conditions of stimuli and stretch on the control of 3D shape changes of SMPs will be studied. This strategy will enrich shape-changing behaviors of SMPs and extend the applications scope.

形状记忆聚合物（SMP）可在外场刺激下改变形状，近年来被广泛研究，但其三维形状难以室温下获得、且变形行为单一。另一方面，一些聚合物可通过链段的受迫取向或应变诱导结晶发生塑性变形。基于此，本项目提出“可逆交联调控受限塑性变形”这一SMP三维变形新策略：基于聚环氧乙烷和含羧基聚合物制备可塑性变形SMP；通过表面图案化操作，在SMP选定区域引入Fe(III)-羧酸根配位梯度交联以限制链段的运动，使材料被（局部）拉伸时可基于受限的塑性变形弯曲、实现室温下的三维变形；进一步利用可见光和空气（氧气）控制不同区域配位交联的可逆构建，同时综合运用外场（热）刺激和（局部）拉伸诱导，实现材料三维形状的可控转变。研究材料组成、结构与性质、表面图案化操作、配位交联可逆构建、外场刺激和拉伸诱导等对SMP三维塑性变形调控的影响规律，并揭示其内在关联。本策略可使SMP的变形行为更加丰富、灵活，并拓宽其应用前景。

针对目前形状记忆高分子和仿生变形高分子领域存在的可逆且可调变形行为难以实现、光响应变形实现难度大、可逆变形行为单一、刺激手段局限性大等问题，我们引入可光解离铁离子-羧酸根配位交联到上述两类高分子中，获得了以下成果：1. 实现了形状记忆高分子薄膜的三维变形调控，获得了一系列热稳定的三维过渡形状；2. 提出了梯度塑性变形这一创新机制，实现了高分子薄膜的拉伸诱导三维变形；3. 引入铁离子-羧酸根配位交联到水凝胶中，实现了光响应形状记忆行为；4. 利用铁离子-羧酸根配位交联在紫外光下解离的梯度特性，实现了可光调控的水凝胶可逆致动行为；5. 提出了“整体固定-局部梯度解离”设计，实现了光响应形状记忆行为与致动行为的有机结合。本项目研究丰富了形状记忆高分子和仿生变形高分子的设计与制备策略，有利于拓宽这两类高分子的应用前景。