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 bee n produced by batch and semicontinuous emulsion polymerization. The de grees of cross-linking have been measured by DMA and also predicted by computer simulation based on kinetic data. With equilibrium monomer s welling experiments achieved on films made from these polymers, two cu rves of the interaction parameter vs. the polymer fraction have been c omputed. These curves compare favorably with a theoretical model based on a Unifac procedure for the estimation of monomer activity. Two dif ferent data bases, liquid-liquid and liquid-vapor equilibria, have bee n used in the Unifac model. For the polystyrene/n-butyl methacrylate s ystem, a linear relationship found between the interaction parameter a nd composition is both predicted and measured experimentally. In all c ases, this interaction parameter is found to increase with polymer con centration. (C) 1994 John Wiley & Sons, Inc.