True reactivity ratios for styrene-methyl methacrylate copolymerization in bulk

Abstract

The local composition concept has been adopted to account for the monomer partitioning effect in the vicinity of the growing macroradical in radical copolymerization. Local compositions were calculated in a two step procedure. In the first step the activity coefficients were calculated in the assumed model systems using the UNIFAC group contribution method1 UNIFAC means UNIQUAC Functional Group Activity Coefficients, where UNIQUAC stands for Universal Quasichemical Activity Coefficients. . Subsequently, the modified Wilson equation was applied for estimation of the Boltzmann factor in the derived formulae. Terminal and penultimate models for the bulk copolymerization were investigated. For both models corresponding formulae were derived relating copolymer composition with local mole fractions and the true reactivity ratios. Test calculations have been performed for the bulk styrene-methyl methacrylate system at 313.15 K.