流变-红外联用研究典型应力刚化水凝胶的分子作用机制

Stress-stiffening hydrogels, which are very common in nature, can become stiffer as the stress in the material increases. Such behavior of biopolymer hydrogels plays a key role in preventing damage under external stress, regulating motility modes and differentiation of cells, enabling long-range signaling between cells. Moreover, synthetic stress-stiffening hydrogels hold great potential in the fields of tissue engineering and regenerative medicine. Even though, the stress-stiffening mechanism with regard to molecular interactions still remains unclear. Applying simultaneous rheometry-FTIR spectroscopy and two-dimensional correlation spectroscopy, this project mainly aims to study the gelation process and stress-stiffening mechanism of several typical hydrogels (such as hydrogels based on methyl cellulose and oligo(ethylene glycol)-functionalized polyisocyanopeptides) from the molecular level. In this project, we will mainly focus on the molecule interactions and their corresponding variations under external stress, which would help us better understand the origin of stress-stiffening behavior in nature as well as guide the structure design and performance optimization of biomimetic stress-stiffening hydrogels.

应力刚化水凝胶作为自然界中广泛存在的一类凝胶材料，其刚度可随施加外界应力的增加而增大。生物大分子水凝胶的应力刚化行为在抑制应力造成的损伤、调节细胞运动模式和分化、促进细胞间的远程信号传输等方面起到关键作用，而人工合成的应力刚化水凝胶，在组织工程和再生医学等领域有着重要应用前景。基于目前对应力刚化水凝胶分子尺度相互作用机制的认知不足，本项目拟围绕几类典型的应力刚化水凝胶(如甲基纤维素、寡聚乙二醇功能化多肽聚异腈水凝胶等)展开研究，利用流变-红外联用和二维相关光谱技术，我们将从分子水平探讨体系的凝胶化过程以及应力刚化响应机理。项目的研究意义在于从分子水平揭示应力刚化水凝胶的相互作用机制，并帮助理解生命体中此类响应行为的分子机理，从而为新型仿生应力刚化水凝胶的结构设计和性能优化提供研究思路和理论指导。

生物基大分子水凝胶大都表现出应力刚化行为，其刚度可随施加外界应力（应变）的增加而增大。然而，这类生物基大分子水凝胶内部的相互作用机制目前仍存在一定的认知不足。针对这一问题，本项目从纤维素（及其衍生物）、琼脂糖等典型体系入手，重点利用流变、红外光谱以及流变-红外联用等技术，结合二维相关光谱分析，开展了系列构效关系研究：（1）甲基纤维素水溶液热致溶胶-凝胶转变机理，表明特征分子基团（如C-O）的脱水过程略先于体系溶胶-凝胶转变的发生，且体系的溶胶-凝胶转变与氢键、疏水相互作用密切相关；（2）甲基纤维素基高强度应力刚化水凝胶的制备，通过在甲基纤维素水溶液中加入甲基丙烯酸，调控疏水相互作用和氢键，采用一锅法聚合得到高强度甲基纤维素/聚甲基丙烯酸超分子水凝胶，该水凝胶表现出应力刚化行为；（3）琼脂糖水溶液的热致溶胶-凝胶转变行为，探讨了不同霍夫曼斯特序列阴离子对其影响机制，研究了琼脂糖-无机盐-水分子之间的相互作用机理；（4）基于尿素水溶液在纤维素中的扩散过程，探讨了纤维素-水-尿素之间的相互作用机制。本项目涉及的研究结果，有效阐释了生物基多糖大分子水凝胶的结构-性能关系，对于相关材料的开发和应用具有重要的指导意义。