基于接枝微球的可控剪切增稠凝胶及其流变机理研究

Focusing on the problem of the poor realizability and controllability of shear-thickening characteristic in gels, the graft microspheres and responsive gels will be investigated as the research objects in order to develop the smart gels with shear-thickening character and responsiveness, which have great potential application in the fields of physical protection, tissue engineering and so on. Based on the design of molecular structure, the graft micropheres with different macromolecular chains will be prepared by living controllable graft polymerization, and the rheological behavior of graft microsphere suspensions under the environmental change will be researched systematically. The effect of the graft macromolecular chains and environmental response on the rheological behavior and the shear-thickening character will be discussed. The mechanism of macro- and micro-interaction in the systems affecting the shear-thickening character will be revealed, and the relative mechanism model will be established. Moreover, based on the mechanism, the graft microspheres will be incorporated into the responsive gels to prepare the responsive gels with shear-thickening character, and the influence of macroscopic and microscopic factors on the properties of gels will be analyzed. The method for controlling the shear-thickening behavior by responsiveness will be defined, and the mechanism of rheological and shear-thickening behavior will be revealed. This project will establish the relevance between the structure of graft microspheres and the shear-thickening behavior, and achieve the effective control of shear-thickening behavior in gels. Furthermore, the mechanism of shear-thickening in the systems with complex interaction will be illuminated. This research will be of significance in the shear-thickening systems and smart gel materials.

针对凝胶中难以实现和控制剪切增稠特性的问题，以接枝微球、响应凝胶为研究对象，开展在物理防护、组织工程等领域具有广泛应用前景的刺激响应剪切增稠凝胶的研究。通过分子结构设计，以活性可控聚合制备表面具有不同大分子链的接枝微球，研究其悬浮体系在环境变化下的流变行为，探讨接枝大分子链特性和环境响应对体系流变性及剪切增稠特性的影响规律，揭示体系内宏-微观相互作用对剪切增稠行为的影响机理，建立机理模型；结合机理设计体系，将接枝微球引入响应凝胶中，制备可剪切增稠的多刺激响应凝胶，分析宏、微观因素对凝胶性能的影响，明确通过刺激响应控制凝胶剪切增稠行为的方式，揭示凝胶流变性和剪切增稠行为机理。项目预期将建立接枝微球结构与剪切增稠行为之间的内在关联，在凝胶中实现对剪切增稠行为的有效控制，进一步明确存在复杂相互作用体系的剪切增稠机理，对剪切增稠体系和智能凝胶材料的开发具有重要意义。

本课题主要针对微球悬浮体系及微球复合凝胶的流变性及发生的剪切增稠行为相关的科学问题，开展了系列研究工作。研究主要通过表面改性、活性可控聚合在不同粒径硬质二氧化硅微球表面接入不同大分子链和改性基团，如接入PNIPA、PMMA聚合物链， -NH2、-COOH基团等，并对微球物性和表面基团结构进行了细致分析。将以上表面改性微球与不同分散介质复配得到多种悬浮体系，探明悬浮体系在不同流变测试模式（动态、稳态）、环境变化（温度，pH 值）下的流变行为，尤其是剪切增稠特征，明确环境变化、体系组成、介质特性、微球表面链特征等因素对流变行为的影响规律，分析了宏、微因素及体系中各组分间相互作用对剪切增稠行为的影响机理，采用不同的机理模型如硬球斥力模式、电荷稳定微粒模式、摩擦机理对其剪切增稠特性进行分析，实现对悬浮体系剪切增稠起始点的预测及对剪切增稠程度的预测分析，得到了较好的预测效果。得到了通过环境指标调节、表面结构控制以实现对剪切增稠特性进行调控的方式。研究还对接枝改性微球悬浮体系的受力松弛行为、应力历史影响、稳、动态流变行为的拟合等进行了探索。. 结合以上机理和模式，研究将不同表面改性二氧化硅微球引入温度刺激响应凝胶、甲壳素凝胶中，制备得到不同纳米复合凝胶，对凝胶的流变特性进行了探索，明确了微球及表面接枝特性、凝胶组分、交联密度，合成方式等对流变特性的影响，建立了各因素对凝胶储能模量、耗损模量、对冲击抵抗能力的相互关系，并阐释了内在机理。同时，还将其他纳米粒子如笼型聚倍半硅氧烷粒子、纳米纤维素等引入不同类型响应性凝胶及生物质凝胶中，系统的研究了不同凝胶的基础性能如力学性能、溶胀特性、响应速率等，尤其是详细的探索了纳米粒子特性对流变特性的影响，并阐述其机理。研究还以不同的药物为标的研究了其药物负载和缓释性以进一步拓展其应用。. 研究进一步明确了存在复杂相互作用体系的剪切增稠机理，对剪切增稠体系和智能凝胶材料的开发具有重要意义。