纳米填料几何结构对聚合水凝胶力学增强的影响及增强机理

Polymer hydrogels with excellent mechanical strength and soft-wet nature are highly desired in the applications of tissue engineering scaffold, controlled release vehicle, wound dressing and biosensor. However, polymer hydrogels prepared in the presence of organic crosslinkers were used to be considered as a class of mechanically weak materials due to the lack of effective energy dissipation mechanism. Integration of both excellent mechanical strength and soft-wet nature in highly water contained polymer hydrogel has become a reality by three kinds of effective reinforcement strategies, which are double network interpenetration, topological crosslinking and nanoparticle reinforcement. Among all these strategies, nanoparticle reinforcement is more attractive due to its universality. This project will focus on the effect of the geometry structures of nanofillers on the reinforcement of organic molecule crossslinked polymer hydrogel. Solvent relaxation NMR and dynamic rheology technologies will be used to reveal the relationship between the nanofillers/polymer chains interaction strength and the geometry structures of the nanofillers. Further, the conformation of polymer chains will be adjusted by introducing comonomers into the polymer 3D network to match the geometry structures of the nanofillers, hoping to construct steady and effective energy dissipation mechanism to the polymer 3D network by enhancing the interaction between nanofillers and polymer chains. Then, these efforts will be applied to construct nanocomposite polymer hydrogels with adjustable mechanical strength and soft-wet nature in the presence of organic crosslinkers and nanofillers with different geometry structures.

聚合物水凝胶因其类似于生物组织的高含水量而具备优异的生物相容性，在组织工程、药物释放、伤口敷料以及生物传感等领域有着广泛的应用。如何在保持水凝胶固有特性的同时提高其综合力学强度一直是水凝胶研究领域努力的方向。现有的三类水凝胶增强方案中纳米复合水凝胶以无机纳米颗粒作为物理或化学交联剂，较低的添加量即可实现对聚合物水凝胶力学性能的显著提升，对聚合物水凝胶增强相关研究更具普适性。前期预实验表明，其他条件一致情况下，纳米填料的几何结构对聚合物水凝胶力学增强效果有较为显著的影响。基于此，本项目拟从纳米填料几何结构的角度出发，通过严格的对比实验确认纳米填料几何结构对聚合物水凝胶力学增强效果的贡献及增强机理，并在此基础上通过高分子链性质的调整来匹配纳米填料的几何结构，以期增强二者之间的相互作用强度，建立稳定而又高效的能量耗散体系，实现对化学交联水凝胶综合力学强度的显著提升。

传统聚合物水凝胶以水溶性单体和化学交联剂为构筑单元，聚合过程中形成的非均匀交联网络使得相邻交联点之间的分子链长度分布较宽。由于缺乏有效的能量耗散机制，外力作用下此类水凝胶易发生应力集中效应，高分子三维网络易发生脆裂，水凝胶表现出较低的力学强度。向化学交联网络中引入纳米填料或直接以纳米填料为交联点，借助纳米颗粒在聚合物网络中的良好分散来避免应力集中效应，通过提高交联网络的均匀化程度实现应力在整个网络的传递进而实现聚合物水凝胶的增韧。本项目主要从纳米颗粒几何结构入手，通过系列实验以及先进表征技术明确了纳米填料表面几何结构对高分子/纳米颗粒相互作用的贡献，探索了影响二者相互作用的一般规律，并以此为基础构建了具有优异力学性能的纳米复合水凝胶。基于此项目基础研制的超弹性水凝胶有望作为电阻型应力传感器应用于高灵敏、高保真动态行为监测。相关研究结果对水凝胶材料增韧以及超弹性水凝胶制备提供了新的思路。