ABSTRACT:The monomer reactivity ratios for styrene/ 2-ethylhexylacrylate in bulk at 80°C were investigated by studying the resulting copolymer composition via 1 H-NMR. Composition results were summarized and various methods were employed to estimate the reactivity ratios including the use of the Error-in-Variables-Model (EVM) approach by using the Mayo-Lewis model. The estimates of the reactivity ratios from the EVM method are found to be r s ϭ 0.979 and r EHA ϭ 0.292. The resulting copolymer has a tendency toward alternation with an azeotrope of f(styrene) ϭ 0.972.