Homo-oligomerization of maleic anhydride in nonpolar solvents: A kinetic study of deviations from nonlinear behavior

Deviation from nonlinear first order polymerization kinetic models is usually observed for cases where steric effects are dominant. A kinetic model was developed for the homo-oligomerization of bulky maleic anhydride units. Factors affecting the kinetics of homo-oligomerization of maleic anhydride have also been studied using two different initiators, azoisobutyronitrile (AIBN) and benzoyl peroxide, at 10 mol % concentrations in two different solvents o-xylene and toluene. Maleic anhydride polymers having a number average molecular weight by SEC, between 300 and 900, and a polydispersity of between 1.0 and 2.0 were observed, and data were justified by the model. The molecular weight of the polymers increased with the conversion, and steric effects dominated at higher molecular weight as observed from the decrease in magnitude in the corresponding termination rate constants. The model values of conversion were compared with experimental data and cross verification of the model was done using molecular weight calculations. The present model represents the data with an average error of less than 5% over the entire experimental range. (c) 2006 Wiley Periodicals, Inc.