Coefficient of Performance for the Volume Phase Transition Process of Polymer Gels

Abstract

A Clapeyron-type equation to estimate the thermodynamic properties of the volume phase transition under load have been derived on the basis of the triphasic equilibrium. The expression for the coefficient of performance is also derived for the transition process. Experiments by using a poly(N-isopropylacrylamide) gel are made to investigate the detailed nature of the volume phase transition of the gel under tension. The coefficient of performance at the transition process for the gel increases with increasing tension and is analyzed by the Clapeyron-type equation presented.