A COMPARISON OF METHODS FOR THE ESTIMATION OF POLYMER MONOMER INTERACTION PARAMETERS - THE POLYSTYRENE N-BUTYL METHACRYLATE SYSTEM

To measure the polymer/monomer interaction parameter as a function of composition, a set of partially cross-linked synthetic latices has been produced by batch and semicontinuous emulsion polymerization. The degrees of cross-linking have been measured by DMA and also predicted by computer simulation based on kinetic data. With equilibrium monomer swelling experiments achieved on films made from these polymers, two curves of the interaction parameter vs. the polymer fraction have been computed. These curves compare favorably with a theoretical model based on a Unifac procedure for the estimation of monomer activity. Two different data bases, liquid-liquid and liquid-vapor equilibria, have been used in the Unifac model. For the polystyrene/n-butyl methacrylate system, a linear relationship found between the interaction parameter and composition is both predicted and measured experimentally. In all cases, this interaction parameter is found to increase with polymer concentration. (C) 1994 John Wiley & Sons, Inc.