Concentration dependence of the sol-gel transition point and the network formation of polymer gels

We report the experimental and the numerical studies on the sol-gel transition phenomena of polymer gels in terms of the solution effect. We found that the sol-gel transition boundaries of polymer chemical gels are described by a Linear function of the polymer concentration. These results tan be successfully explained by the percolation model of thermally reversible physical gels, provided that we estimate that contribution of isolated bonds and subtract it from this model. We also extend this model to explain the molecular weight effect that is peculiar to polymers. The molecular weight dependence of the decrease of the transition boundary for polymer solutions is explained by the effect of both the connectivity and configuration of polymer chains. It is clearly revealed that the concentration dependence of the gel transition boundary for polymer gels can be described in the same framework as physical gels, despite the large difference in the cross-link features.