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Study on methodology for critical behavior near the sol-gel transition point

溶胶-凝胶转变点附近临界行为的方法研究

基本信息

批准号：
02556015
负责人：
YANO Toshimasa
金额：
$ 10.5万
依托单位：
The University of Tokyo
依托单位国家：
日本
项目类别：
Grant-in-Aid for Developmental Scientific Research (B)
财政年份：
1990
资助国家：
日本
起止时间：
1990 至 1991
项目状态：
已结题

项目摘要

Not only Mechanical properties, which give macroscopic features of gels, but also light scattering, which gives features of gels on molecular level, were measured in order to analyze the critical phenomena near the sol-gel transition point.dynamic light scattering method was carried out to determine the sol-gel transition point. From the fluctuations of scattered light intensity in the course of time, auto-correlation function was measured, and then by using Stokes-Einstein equation, cluster radius was calculated from the diffusion constant which was obtained from the correlation function. Results suggested that first, primary clusters were formed, and then the primary clusters polymerized with each other to form larger secondary clusters. The size of secondary clusters showed a tendency to diverge when the concentration approached the gelation point. By fitting the data with scaling law, the critical exponent was determined to be 0.84, which is not so far off from the critical exponen … More t of correlation length in percolation theory, which is said to be 0.9.In the case of agarose, which forms clusters by non-covalent bonds, it was also possible to determine the cluster radius of agarose sol by using the dynamic light scattering method. Average cluster radius showed a tendency to diverge when the concentration increased and approached the sol-gel transition point. It was also possible to fit the data with scaling law, and the gelation concentration and the critical exponent were determined to be 4.5*10^<-3>(wt%) and 0.98 at the temperature of 27ﾟC.When the temperature was lowered and approsched the gelation temperature, the cluster radius became larger. By fitting the data, the gelation temperature and the critical exponent were determined to be 32.7ﾟC,and 1.36, for 0.15(wt%) agarose sol. The critical exponent thus obtained was larger than the theoretical value.From the above results, it was suggested that by measuring the cluster radius distribution, concepts of percolation and scaling were shown to be effective when determining the physical property changes near the sol-gel transition point. Less

为了分析溶胶-凝胶转变点附近的临界现象，不仅测量了表征凝胶宏观特征的力学性能，而且测量了表征凝胶分子水平特征的光散射，并采用动态光散射法测定了溶胶-凝胶转变点。从散射光强度随时间的变化，测量了自相关函数，然后利用Stokes-Einstein方程，由自相关函数得到的扩散常数计算了团簇半径。结果表明，首先形成初级团簇，然后初级团簇相互聚合形成更大的次级团簇。当浓度接近凝胶点时，次级团簇的大小有发散的趋势。用标度律对实验数据进行拟合，得到临界指数为0.84，与实验值相差不大 ...更多信息在渗滤理论中相关长度的t，据说是0.9。在琼脂糖的情况下，它通过非共价键形成团簇，也可以通过使用动态光散射方法来确定琼脂糖溶胶的团簇半径。团簇平均半径随浓度的增加而增大，并逐渐接近溶胶-凝胶转变点。在27 ℃时，凝胶浓度和临界指数分别为4.5 × 10 ~ 4<-3>（wt%）和0.98，当温度降低到接近凝胶温度时，团簇半径增大。通过对数据的拟合，确定了0.15（wt%）琼脂糖溶胶的胶凝温度和临界指数分别为32.7 ℃和1.36。由此得到的临界指数大于理论值。从以上结果可以看出，通过测量团簇半径分布，逾渗和标度的概念在确定溶胶-凝胶转变点附近的物理性质变化时是有效的。少