Thermodynamic Theory of Equilibrium Copolymerization

Abstract

General equations are derived for the thermodynamics of equilibrium copolymerization based on the diad model of copolymer. Physical interactions between components in solution are taken into consideration. Several special cases are treated in detail. When these physical interactions are absent, the relations obtained from the theory agree completely with those derived from the kinetics. Equilibrium monomer concentrations are illustrated as functions of excess free energy due to formation of heterodiad, equilibrium constants of homopolymerization, and initial monomer concentrations. It is shown that when the physical interactions are present, their effects cannot be ignored even in dilute solution. In bulk copolymerization, the physical interactions have a considerable effect on equilibrium, especially when the equilibrium monomer volume fractions are relatively small.