Phase Transitions of Gels

Abstract

Polymer gels are known to exist in two distinct phases, swollen and collapsed. Volume transition occurs between the phases either continuously or discontinuously in response to chemical and physical stimuli such as temperature, solvent composition, pH, ionic composition, electric field, light, and particular molecules. For a gel to undergo the phase transition, it is necessary that polymers interact with each other through both repulsive and attractive interactions and the balance of competing interactions has to be modified by various stimuli. The phase behavior of a gel, therefore, crucially depends on the nature of interactions between polymers. Recently new phases and volume transitions between them have been discovered in some gels. Detailed examination of the gel phase behavior provides a deep insight into the polymer-polymer interactions and configurations of polymers. The knowledge on physical and chemical fundamentals of gel phase transition will play a role as guiding principles for a wide variety of technological applications of gels as functional elements.