Monomer‐to‐water ratios as a tool in controlling emulsion copolymer composition: The methyl acrylate–indene system

Abstract

AbstractA drifting copolymer composition as a function of conversion is an aspect typical of copolymerization. Reducing this so‐called composition drift in batch copolymerizations will lead to a decrease in chemical heterogeneity of the copolymers formed. For monomer systems in which the more water‐soluble monomer is also the more reactive one, theory predicts that composition drift in emulsion copolymerization can be reduced or even minimized by optimizing the monomer‐to‐water ratio. The monomer combination methyl acrylate–indene (MA–Ind) meets the requirements needed to minimize composition drift in batch emulsion copolymerization. Therefore, this monomer combination is chosen as a model monomer system in order to verify this theoretical prediction. Reactivity ratios needed for model predictions have been determined by low conversion bulk polymerization, resulting in rMA = 0.92 ± 0.16 and rInd = 0.086 ± 0.025. Furthermore, emulsion copolymerization reactions at the same monomer mole fraction are performed at different monomer to water ratios. From the good agreement between experiments and theoretical predictions for MA–Ind, it was concluded that control and even minimization of composition drift in batch emulsion copolymerization for monomer systems in which the more water‐soluble monomer is also the more reactive one is indeed possible by changing the initial monomer‐to‐water ratio of the reaction mixture provided that the reactivity ratios of both monomers are not too far from unity. © 1994 John Wiley & Sons, Inc.