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

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性质的力学性质，还测量了反映凝胶分子水平特征的光散射，并用动态光散射法确定了凝胶转变点。根据散射光强度随时间的起伏，测量自相关函数，然后利用斯托克斯-爱因斯坦方程，由相关函数得到的扩散常数计算团簇半径。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生团簇。当浓度接近凝胶点时，二次团簇的大小有发散的趋势。用标度律对数据进行拟合，确定其临界指数为0.84，与临界指数…相差不大在琼脂糖通过非共价键形成团簇的情况下，也可以用动态光散射法测定琼脂糖溶胶的团簇半径。随着浓度的增加，平均团簇半径有发散的趋势，并接近溶胶-凝胶转化点。在27ﾟC时，凝胶浓度和临界指数分别为4.50×10~(-3)(wt%)和0.98。温度越低，凝胶半径越大。通过对数据的拟合，确定了0.15(wt%)琼脂糖凝胶的凝胶化温度和临界指数分别为32.7ﾟC和1.36。从以上结果可以看出，通过测量团簇半径分布，渗流和标度概念在确定溶胶-凝胶转变点附近物性变化时是有效的。较少

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