力-热-化耦合作用下物理凝胶的交联变化及相变机理研究

In general, physical hydrogel is crosslinked by polymer chains via physical bonds, such as hydrogen bonding and van der Waals interactions, which may be formed and broken dynamically subject to environmental stimuli, resulting in sol-gel phase transition. Literature search reveals that the previously published studies mainly focused on the behavior of equilibrium state and the critical condition for phase transition, while the dynamic breaking and forming of physical crosslinks and its influence on the phase transition remain unclear. The present project plans to investigate the interactions of physical crosslinks, microscopic structure and macroscopic behavior subject to the thermo-chemo-mechanical coupled fields, in order to further modify the formulation for the free energy of physical hydrogel by accounting for the effect of crosslink density. The governing equations and constitutive relations may be formulated based on principles of thermodynamics and continuum mechanics, including the kinetic equation for the dynamic change of physical crosslinks. Then, the coupling among the crosslink change, deformation, heat transfer and diffusion may be numerically investigated, in order to reveal the fundamental mechanism for the dynamic change of crosslink density subject to multiphysical effects, and its influence on the change of mechanical properties among elasticity, viscoelasticity and viscosity, as well as the sol-gel phase transition for physical hydrogel. The results may provide a theoretical guideline for design, preparation, and performance prediction for physical hydrogel.

物理凝胶由高分子链条通过氢键、范德华力等物理作用力相互交联形成，环境刺激会改变其交联网络，引起溶胶-凝胶相变。目前，其平衡态行为和相变临界条件等现象得到了广泛关注，而物理交联的动态变化及其对物理凝胶力学性能和相变的作用机理尚未明晰。本项目拟从热力学与连续介质力学原理出发，分析力-热-化学耦合作用下物理交联与微观结构和宏观行为的联系，研究物理交联密度对自由能的影响，完善物理凝胶的自由能模型。建立物理凝胶力-热-化学耦合本构关系和控制方程，以及交联密度动态变化的运动学方程。通过理论分析和数值模拟，探索多场作用下物理交联变化与变形、热传导和扩散等物理化学行为的耦合作用，阐明交联密度的动态变化规律，揭示其对物理凝胶弹性、粘弹性、粘性等力学性能改变和相变的作用机理。本项目将为新型物理凝胶的设计、制备及性能预测提供理论依据。

物理凝胶由高分子链条通过氢键、范德华力等物理作用力相互交联形成，环境刺激会改变其交联网络，引起溶胶-凝胶相变。目前，其平衡态行为和相变临界条件等现象得到了广泛关注，而物理交联的动态变化及其对物理凝胶力学性能和相变的作用机理尚未明晰。本项目从热力学与连续介质力学原理出发，分析了力-热-化学耦合作用下物理交联与微观结构和宏观行为的联系，研究了物理交联密度对自由能的影响，完善了物理凝胶的自由能模型。建立了物理凝胶力-热-化学耦合本构关系和控制方程，以及交联密度动态变化的运动学方程。通过理论分析和数值模拟，探索了多场作用下物理交联变化与变形、热传导和扩散等物理化学行为的耦合作用，阐明了交联密度的动态变化规律，揭示了其对物理凝胶弹性、粘弹性、粘性等力学性能改变和相变的作用机理。本项目将为新型物理凝胶的设计、制备及性能预测提供理论依据。