基于大尺寸、能量耗散型断裂过程区增韧设计的天然纤维复合水凝胶

Inspired by the structural characteristics of animal’s load-bearing fibrous tissues (e.g., ligaments), the design of fiber reinforced composite hydrogels provides a new idea to the development of tough hydrogels. However, most of synthetic hydrogels are soft and brittle, and thus lack energy dissipation ability. Furthermore, hydrogels are generally highly hydrated and also swell easily in water, so that effective fiber-hydrogel interfaces are difficult to form between them. These problems hinder the development of fiber reinforced composite hydrogels severely. To overcome the obstacles, in this project we propose to combine energy-dissipative physical hydrogel matrices and natural fiber fabrics, where effective interfaces based on hydrogen bonds or ionic bonds could be formed, to fabricate fiber reinforced composite hydrogels. Based on the design of large and energy-dissipative fracture process zones, the aim of the project is to provide a fabrication method for achieving the fiber reinforced composite hydrogels with superior fracture toughness. By regulating the physical and chemical structural parameters of both the hydrogel matrices and fiber fabrics, the mechanical behaviors are systematically investigated. In addition, the relation between the fracture modes and fracture toughness as well as mechanism are also understood to reveal the influences of the structures of both the matrices and fiber fabrics on the mechanical properties of the composite hydrogels. Meanwhile, the toughening mechanism of the composite hydrogels is also disclosed from the matrix toughness, the interfacial interaction, and the fracture strength of the natural fibers aspects, respectively. The universality of the toughening mechanism is further verified by varying energy-dissipative matrices. We hope that this project could provide a new approach on the development of hydrogel-based soft materials with high mechanical properties.

受动物承重型纤维组织（如韧带）结构特征启发，纤维增强复合水凝胶为开发强韧性水凝胶提供了新思路。然而，水凝胶大多软而脆，缺乏能量耗散能力，且一般高度水合并在水中易显著溶胀，导致很难形成“纤维-水凝胶”有效界面，极大阻碍了纤维增强复合水凝胶的开发。针对这一难题，本项目基于大尺寸、能量耗散型断裂过程区的增韧设计，拟采用柔韧性物理水凝胶作为能量耗散型基体与高强度天然纤维编织物复合，并在二者间通过氢键或离子静电作用形成有效界面，构建超高韧性天然纤维复合水凝胶的制备方法。通过调控水凝胶基体与纤维编织物的物理、化学结构研究复合水凝胶的力学行为，建立破坏模式与断裂韧性及机理间的对应关系，揭示基体及纤维编织物结构对复合水凝胶力学性能的影响规律；并探究基体韧性、“纤维-水凝胶”界面强度及纤维断裂强度因素与复合水凝胶断裂韧性的关系，阐明复合水凝胶的增韧机理及其普适性，以期为开发高力学性能水凝胶软材料提供新方法。

针对传统高分子水凝胶因缺乏能量耗散机制导致力学性能较弱及网络中的高含水量导致其与固体表面低黏附等科学问题，本项目基于“牺牲键”原理、多重能量耗散机制及多级结构设计策略，通过自由基溶液聚合法及溶液浸泡法等方法制备了一系列强韧性高分子复合水凝胶材料。系统研究了不同金属离子配位、外力诱导作用、透析时间等因素对复合水凝胶的物理化学结构、流变行为、力学行为、断裂行为及自恢复性能的影响规律，建立了水凝胶网络演变的微观模型，探究了纤维含量、界面作用等对复合水凝胶的力学行为、破坏模式、强韧化机理及界面黏附等影响，还采用Mooney-Rivlin理论模型讨论了上述因素对复合水凝胶应变软化和硬化行为的影响，并进一步采用粘弹性理论模型讨论了复合水凝胶网络中粘弹性和弹性的贡献及其在各影响因素作用下的变化规律，有效揭示了水凝胶体系的网络结构演变及强韧化机理，并选用不同水凝胶体系探究了所提出强韧化策略的普适性规律，最后还探究了所制备水凝胶体系在柔性传感、智能刺激响应及抑菌等领域的应用。该研究不仅为强韧性高分子水凝胶的基础研究提供了一些新见解，还为制备强韧性高分子水凝胶材料提供了新方法。在该项目执行期间，共发表学术论文12篇（SCI论文11篇），其中第一/通讯作者论文5篇，包括在高水平学术期刊Adv. Funct. Mater.发表论文1篇；申请国家发明专利5项，其中授权2项；培养5名硕士研究生、8名硕士本科生，并参加学术会议2人次。