明胶水溶液分形性质的光散射研究

Light scattering study of fractal properties in aqueous solutions of gelatin

本文通过动态光散射技术并结合静态光散射及粘滞系数实验研究了明胶水溶液在不同温度、不同浓度下的分形性质。当Ｔ＞Ｔｇｅｌ时（Ｔｇｅｌ为胶凝临界温度），水为明胶的良好溶剂。明胶分子在水溶液中符合自避无规行走模型，分维ｄｆ＝５／３。当Ｔ＜Ｔｇｅｌ时，明胶水溶液需经历从溶液到凝胶的胶凝过程。在胶凝过程中，动态光散射弛豫谱分段具有指数衰减和随后的伸展指数两种模式，且伸展指数衰减的宽度参数β逐渐从０．８减少到胶凝点的０．６７，与此相对应，分维由５／３逐渐增加到２．０。在胶凝点，通过静态光散射及粘滞系数实验测得分维为２．０。

The fractal properties of aqueus solutions of gelatin of different concentration were studied in this paper at different temperature using light scattering (dynamic and static) and viscosity experiments. When T>T gel (T gel is the critical temperature of gelation), water is a better solvent of gelatin, the gelatin molecules in aqueous solutions can be described using self avoid walk mode, i.e. its fractal dimension equals 5/3. When T<T gel the aqueous solutions of gelatin experience a phase change from sol to gel. In the sol gel processes the relaxation spectrum of dynamic light scattering was found to be an exponential decay followed by a streched exponential decay and the width exponent β decreased from 0 8 to 0 67. It means that the fractal dimension d f increased from 5/3 to 2. The static light scattering and viscosity expriments also got the same result of d f at the gel point.