改性石墨烯增强纳米复合双网络水凝胶的合成及机理研究

Intelligent hydrogels, which can change their swelling behavior and other properties in response to environmental stimuli, have attracted great attention in biomedical fields. However, conventional intelligent hydrogels always exhibit very low response rate and weak mechanical properties. Graphene can be used as a reinforcing agent to prepare nanocomposite hydrogels because of its extraordinary mechanical properties. Meanwhile, double network hydrogels not only have good mechanical properties but also be multi-responsive. Based on our previous work, we intend to prepare novel nanocomposite double-network hydrogels with modified graphene as the crosslinker and reinforcing agent. N-isopropylacrylamide is used as the monomer to prepare the first network and acrylic acid is used to prepare the second network through photopolymerization. The effects of modified graphene content, the water content of hydrogels and polymer ratio on various physical properties such as mechanical properties, pH- and temperature responsive properties and swelling properties are investigated. On the basis of the micellar copolymerization therory, the statistical molecular theory of rubber elastic and the Mooney-Rivlin theory, combining with comprehensive characterization,formation mechanism of cross-linked network structure of modified graphene strenghthened hydrogels are studied.We further investigate the biological compatibility, safety and drug release properties. The results will provide theoretical and experimental bases for the preparation and application of graphene-strengthened hydrogels.

智能水凝胶能对外界刺激响应，在医用领域具有诱人的前景。传统智能水凝胶存在响应速率慢、机械性能差等缺点。石墨烯力学性能优良，可望作为增强剂用于制备纳米复合水凝胶。双网络水凝胶不但具有良好的力学性能，也能实现水凝胶的多重响应性。本项目在前期工作的基础上，以N-异丙基丙烯酰胺为单体，通过光聚合方法以改性石墨烯为交联剂构建一个纳米复合网络，之后将丙烯酸聚合制备第二网络，得到改性石墨烯增强的纳米复合双网络水凝胶。研究改性石墨烯用量、含水量、聚合物比例等因素对其力学性能、温敏性和pH敏感性、溶胀性能等的影响规律。综合采用胶束共聚理论、橡胶弹性统计理论和Mooney-Rivlin理论，结合全面的性能测试与表征，对改性石墨烯增强水凝胶交联网络形成机理进行探讨，阐明改性石墨烯在体系中的增强机理，并进行初步的生物相容性、安全性及释药性能研究。本项目获得的结果将为石墨烯增强水凝胶的制备与应用奠定理论基础。

水凝胶基于其优异的溶胀/消溶胀特性、对外界刺激的响应性及生物相容性，使其不仅在日常生活中得到了广泛的应用，而且在药物传输、化学分离等方面也有着良好的应用前景。但是，由于传统水凝胶较差的机械性能，很大程度上限制了水凝胶的应用。因此，如何提高水凝胶的机械性能，同时发展其功能性已经成为近年来科学界的一个具有挑战性的重要课题。本文主要以氧化石墨烯、表面改性氧化石墨烯、无机粘土作为为交联剂，分别制备了具有较好机械性能和一定功能性的的半互穿聚合物网络(semi-IPN)水凝胶及双网络(DN)纳米复合水凝胶。主要研究工作如下：.1. 采用无机氧化石墨（GO）作为添加剂，首先，通过原位自由基聚合的方法，以NIPAM作为单体，有机物N,N´-亚甲基双丙烯酰胺(BIS)为交联剂制备了单网络的PNIPAM传统水凝胶；然后，将其静置于一定浓度的丙烯酸(AA)水溶液中浸泡48 h达到溶胀平衡；最后，通过紫外光引发的方法制备了一系列PNIPAM/AA/GO双网络纳米复合水凝胶。实验结果表明，PNIPAM/AA/GO水凝胶的溶胀/消溶胀速率明显好于传统水凝胶的溶胀/消溶胀速率，并且随着外界温度的升高，PNIPAM/AA/GO水凝胶的消溶胀速率会逐渐加快。更为重要的是，PNIPAM/AA/GO水凝胶的机械性能远远好于传统水凝胶，GO的加入与双网络结构的引进都在很大程度上提高了PNIPAM/AA/GO水凝胶的机械性能。.2. 首先通过氧化法制备了GO，然后用γ-甲基丙烯酰氧丙基三甲氧基硅烷(TMSPMA)对GO进行表面改性；并以TMSPMA改性GO作为交联剂，NIPAM作为单体，SA作为添加剂，成功制备了一系列PNIPAM/SA/GO双重响应的半互穿网络纳米复合水凝胶。此外，以CS 作为pH敏感组分，制备了PNIPAM/CS/GO水凝胶。系统地研究了该水凝胶对外界环境变化的刺激响应性，GO和SA、CS含量对水凝胶各种物理性质的影响。与传统水凝胶相比，PNIPAM/SA/GO和PNIPAM/CS/GO水凝胶不仅具有较高的机械性能，而且具有较快的溶胀/消溶胀速率，对温度的敏感性也大为增强。.3. 采用无机锂藻土作为交联剂，PNIPAM作为紧密交联的第一网络，PAA作为松散交联的第二网络，制备了pH和温度双重响应的PNIPAM/AA/Clay双网络纳米复合水凝胶。系统地研究了锂藻土作为交联剂以及双网络结构