Solvent effects on polymer gels: A statistical-mechanical model

Abstract

A statistical-mechanical model for reversible gelation is developed. This model takes into account solvent effects, which usually are neglected in the classical theory of gelation. The exact solution of this model is given for the limiting case in which "loops" or intermolecular interactions may be neglected (Cayley tree). The general phase diagram is obtained and it is shown that, with a particular choice of a solvent, one can realize the interesting situation in which gelation point and consolute point coincide. This point has peculiar properties associated with the simultaneous divergence of "connectivity" and thermal fluctuations. The recent experimental data of Tanaka and collaborators are in good qualitative agreement with the predictions of the model.