离子原位释放法制备海藻酸/聚丙烯酰胺双网络水凝胶及其结构与性能的研究

Ca-Alginate/PAAm hydrogel is one kind of the physical/chemical cross-linked double network tough hydrogel with the extremely high stretchability and toughness, which was applied from soft electronics to biomedical devices. However, the current method to fabricate the Ca-Alginate/PAAm gel was limited to other ions, and the kinetics of the gelling time was difficult to control, and the resulting gel structure was not homogeneous. Therefore, it is valuable to develop a new method that could fabricate the Alginate/PAAm hydrogel with different ions (eg, Ca and Fe) as ionic crosslinking ions, controllable gelling kinetics, and homogeneous structures, which could facilitate the study of the mechanism of the high mechanical properties and expand its applications. This proposal is planning to utilize a system of D-glucono-gamma-lactone (GDL) and calcium carbonate or ferric citrate complex to fabricate the Ca/Fe-Alginate/PAAm double network hydrogel. The pre-mixed calcium carbonate or ferric citrate complex would in situ release the calcium ions or ferric ions to cross-link with the alginate in solutions when the pH decreases as the GDL hydrolyzes. This as-prepared Ca/Fe-Alginate/PAAm hydrogel should have a more homogenous structure and have more potential to tune the mechanical properties with a larger scope with the different cross-linkers. Then, this proposal plans to systematically study the molecular structure and mechanical, viscoelastic and swelling properties of the as-prepared Ca/Fe-Alginate/PAAm hydrogels, to investigate the structure-properties relationship of these hydrogels. Then, this proposal also plans to fabricate a serial of Ca/Fe-Alginate/PAAm hydrogels with different stress-relaxation properties, which mimic different biological tissues, and fabricate a serial of hydrogels with different swelling properties for controllable drug release. At last, this proposal would study the photo-degradable properties of the Fe-Alginate/PAAm hydrogel and fabricate some photo-responsive functional hydrogels.

海藻酸钙/聚丙烯酰胺水凝胶是一种物理/化学双交联的双网络韧性水凝胶，具有优秀的力学性能，可应用于众多领域。然而，目前此种凝胶的制备方法具有一定的局限性。为了更好的研究该凝胶的增强增韧原理，扩展该凝胶的应用范围，本项目设计研发出一种具有一定通用性、基于离子原位释放的方法，一步制备离子交联高均匀性的海藻酸（钙或铁）/聚丙烯酰胺水凝胶。然后通过分析凝胶双网络聚合物之间的化学反应和相互关系，考察各种因素对凝胶整体力学性能、粘弹性和溶胀性的影响，研究由不同阳离子聚合的海藻酸物理凝胶的破碎、断裂过程和恢复性能，尝试在微观尺度上构建起凝胶的结构-性能关系，进一步理解凝胶的增强增韧机理。同时，利用海藻酸和聚丙烯酰胺凝胶在粘弹性和溶胀性上的差异，制备出一系列具有特定粘弹性或溶胀性的功能性韧性凝胶。最后，系统研究海藻酸铁/聚丙烯酰胺凝胶的光降解性，并利用该凝胶的可控光降解性制备出具有光响应性的功能性凝胶。

海藻酸钙/聚丙烯酰胺水凝胶是一种物理/化学双交联的双网络韧性水凝胶，具有优秀的力学性能，可应用于众多领域。然而，目前此种凝胶的制备方法具有一定的局限性。为了更好的研究该凝胶的增强增韧原理，扩展该凝胶的应用范围，本项目研发出了一种具有一定通用性、基于离子原位释放的方法，一步制备离子交联高均匀性的海藻酸钙/聚丙烯酰胺水凝胶。同时，该方法还扩展到其他离子交联体系，如钴，铜，钡，镧等。为了更进一步理解凝胶制备方法对其力学性能的影响，本项目深入研究对比了一步合成法与浸泡溶剂置换法两种不同保湿抗冻有机水凝胶的制备方法对最终所得凝胶机械性能的影响。我们发现溶剂分子与聚合物之间增强的物理相互作用有利于增强凝胶，而原位聚合凝胶化的溶剂效应或溶剂置换的溶胀作用则会削弱凝胶。这两个相反因素之间的竞争决定了所制备的有机水凝胶的力学性能。更确切地说，溶剂效应或溶胀引起的弱化作用主导着有机水凝胶的力学性能，而增加的物理相互作用所产生的强化作用则起次要作用。为了更进一步理解韧性水凝胶的增强增韧原理，本项目还深入研究了海藻酸钙微凝胶增韧聚丙烯酰胺凝胶体系的增强增韧原理，并证明了微凝胶增韧凝胶与对应的双网络凝胶具有相同的增强增韧原理。在本项目研究过程中，我们发现了一种初始粘度效应对水凝胶结构和性能的影响，即预聚溶液的初始粘度将极大的影响所得凝胶的微观结构和宏观力学性能。这些成果为开发新型功能性水凝胶及其应用提供了技术平台和一定的理论基础。