Kinetics of Phase Transitions of Polymer Gels

本研究旨在建立物理和化学 相变动力学的基本原理 聚合物凝胶;相变是一种普遍现象 在凝胶中发现， 响应于温度的变化大到1000倍， 溶剂组成、pH、离子强度、电场，或 光 这项研究将检查形状的时间过程， 不同尺寸凝胶的局部网络密度和局部应变 和化学组成方面的动力学过程， 相变 膨胀或收缩过程的动力学 凝胶相对于体积的微小变化已经被 建立;它是独特的特点是集体 聚合物网络的扩散系数 无论是否 类似的理论适用于相变动力学， 凝胶体积改变3个数量级是未知的。 到 研究这样一个假设，并建立原则， 相变动力学，这些粘弹性量将 在整个相图中独立确定 凝胶。 摩擦系数和剪切模量将被确定 通过显微镜的方法。 动态光散射和 将使用荧光光漂白恢复光谱。 出现的图案的形成和演化机制 在经历相变的凝胶中， 用公式表示出支配动力学的运动方程 凝胶的过程。 最后，希望能厘清 凝胶内的结构不均匀性， 基本上它们机械、光学和粘弹性 特性.

This research aims to establish the physical and chemical principles which underlie in the kinetics of the phase transition of polymer gels; phase transitions are a phenomenon universally found in gels where they reversibly swell or shrink in volume by as large as 1000 times in response to changes in temperature, solvent compositions, pH, ionic strength, electric field, or light. The research will examine the time course of the shape, local network density and local strain of gels of various sizes and chemical composition in regards to the kinetic processes of a phase transition. Kinetics of a swelling or shrinking process of a gel with respect to a small change in volume have already been established; it was uniquely characterized by the collective diffusion coefficient of polymer network. Whether or not a similar theory applies to the kinetics of phase transition where the gel volume changes by 3 orders of magnitude is unknown. To examine such a hypothesis and establish the principles of kinetics of phase transition, these viscoelastic quantities will be independently determined within the entire phase diagram of gels. Friction coefficient and shear modulus will be determined by microscopic methods. Dynamic light scattering and fluorescence photobleaching recovery spectroscopy will be used. The mechanism of formation and evolution of patterns that appear in gels undergoing a phase transition will be elucidated so as to formulate the equation of motion that govern the kinetic processes of gels. Finally, it is hoped to clarify the origin of structural inhomogeneities within gels which influence substantially their mechanical, optical, and viscoelastic properties.