Solvent effects on the copolymerization of styrene with maleic anhydride: determination of apparent reactivity ratios from the penultimate unit model

-A method for optimization of monomer feed composition to obtain the most accurate reactivity ratios has been described by Tidwell and Mortimer. The proposed method is more generally applicable than for use with the Mayo-Lewis model and copolymer composition vs monomer feed composition data. By means of a simulated example involving the penultimate unit models the effect of experimental design in the determination of reactivity ratios is clearly demonstrated. The same technique is adapted to the copolymerization of styrene with maleic anhydride. Apparent reactivity ratios are obtained for polymerization in toluene, butanone and N,N'-dimethylformamide. There appears to be a significant solvent effect. This paper provides an indication that the highest obtainable accuracy of apparent reactivity ratios depends on the values of the reactivity ratios themselves. Interpretation of the experimental results in terms of the bootstrap model leads to the conclusion that there is no dependence of monomer sequence distribution vs copolymer composition on the solvent. Quantitative interpretation is hampered most probably by the absence of maleic anhydride homopolymerization.