Study on kinetics of copolymerisation of styrene and maleic anhydride in dioxane

Kinetics of the copolymerisation of styrene and maleic anhydride have been studied in dioxane at 50° using azobisisobutyronitrile as initiator. Explanation of the kinetic behaviour has been attempted in terms of the participation in propagation of a charge-transfer complex between the monomers along with propagation via free monomers. It is found that the complex model is able to explain most features of the copolymerisation of these monomers. It has been possible to determine the constants δ₁, δ₂, k_1c/k₁₂, k_2c/k₂₁ and Φ where k_1c/k₁₂ and k_2c/k₂₁ represent the specific rate constants of reaction of a particular type of radical with a dissimilar monomer site of the complex relative to that with a dissimilar free monomer. They are reviewed on the basis of available literature data. The cross-termination factor Φ is found to play an important role in the present system. An approximate value of $\text{k}{}_{\mathrm{t}}{}^{0.5}\text{k}{}_{\mathrm{p}}$ for maleic anhydride could also be found and this probably represents the first reported value for this constant from copolymerisation. The applicability of the generalised penultimate model is also briefly discussed.