自修复弹性体破坏与愈合过程及其物理机制的研究

In the last decade, there has been a significant progress in the molecular design of self-healing elastomers (SHEs) by chemical methods, yet understanding the basic physical mechanisms of the rupturing and healing processes of SHEs evidently falls behind the molecular design. As such, this project will fabricate SHEs with controllable molecular and network structures, and use these SHEs as model systems for investigation. The methods of characterizing ultrathin polymer films and those of characterizing thermodynamics and kinetics of polymers will be adopted to study the fracture surface with macroscopic damage and the bulk with microscopic damage, respectively. The microstructure and molecular chain dynamics will be analyzed in the nonequilibrium state and compared with those in the equilibrium state, to reveal the physical mechanism of material damage. Moreover, we will investigate the evolution dynamics of dynamic bonds, network structure and molecular motion during the healing process from nonequilibrium state to equilibrium state. The obtained dynamic character of multi-scale structures and molecular motion as a function of time will be compared with that of mechanical properties during the healing process, to unravel the physical mechanism of the healing process. The outcomes of this project can be utilized to instruct the molecular design of SHEs with high performance and high healing efficiency, and also to promote the knowledge accumulation and renewal concerning polymer physics, such as dynamic networks and molecular motion.

近年来，通过分子设计制备自修复弹性体已经得到蓬勃的发展，然而从物理角度理解自修复弹性体的破坏与愈合过程及其机制明显滞后。针对这一现实，本项目拟制备分子结构和网络结构可控的自修复弹性体，以其为模型体系，巧妙地利用表征高分子超薄膜的新方法和表征高分子热力学与动力学的传统方法，分别研究产生宏观结构破坏的断面和产生微观结构破坏的本体，分析二者对应的非平衡态的微观结构和分子链动力学，并与初始平衡态的数据对比，揭示自修复弹性体产生破坏的物理机制。进一步探索断面和本体在愈合过程中由非平衡态向平衡态转变时动态键动态特性、网络结构和分子运动的演变，获得不同尺度的结构和分子运动随愈合时间变化的动力学特征，并与材料宏观性能的修复动力学对比，揭示自修复弹性体愈合过程及其物理机制。本项目的研究成果可用于指导高性能和高效愈合自修复弹性体的分子设计，亦可促进高分子动态网络模型和分子运动理论等知识的积累和更新。

目前，关于自修复弹性体自修复机理的研究明显滞后于材料的设计和制备，极大限制了高愈合效率和高力学性能的自修复弹性体的发展。针对这一现状，本项目通过分子设计合成了多种自修复弹性体作为模型体系，剖析了自修复弹性体的分子结构和网络结构特征，深入研究了动态键类型和密度、分子拓扑结构及网络结构对自修复弹性体物理机械性能和自修复效率的影响。在此基础上，通过介电松弛谱、二维红外分析、拉曼光谱和动态流变仪等手段，分析自修复弹性体中不同模式的分子运动，及分子运动对动态键重组和网络结构重组的驱动作用，进而揭示动态键重组和网络结构重组对弹性体自修复效率的贡献。通过共聚反应，将具有聚集诱导猝灭效应或聚集诱导发光效应的荧光分子引入自修复弹性体中，建立了材料破坏和修复过程中损伤应力活化区的可视化和定量化检测技术，通过微区荧光强度变化，测定了损伤应力活化区的尺寸，及其偏离平衡态的程度；进一步，追踪损伤应力活化区从非平衡态向平衡态转变时动态键、网络结构和自由体积的演变，从而在分子尺度上揭示自修复弹性体破坏和愈合的物理机制，为高愈合效率和高力学性能的自修复材料的制备提供了科学依据。项目执行期间在P Natl Acad Sci USA, Mater. Horizons, Adv. Funct. Mater, Chem. Mater, Sci China Mater, J Mater Chem A, ACS Appl Mater Interfaces, Chem Eng J等杂志上发表标注 SCI 论文44篇(其中 IF>10 的期刊论文 21篇)，申请中国发明专利 5项（授权3项），毕业的硕博士研究生12人。

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