Radical copolymerization of 2-ethylacrylic acid and methacrylic acid

Copolymers of 2-ethylacrylic acid (EAA) and methacrylic acid (MAA) were prepared in bulk and in N,N-dimethylformamide (DMF). Although precipitation of the copolymers was observed in bulk, the reaction mixtures remained apparently homogeneous in DMF. Best-fit terminal-model reactivity ratios were determined by a nonlinear least squares technique to be r_MAA = 1.14 and r_EAA = 0.23 in bulk, and r_MAA = 1.91 and r_EAA = 0.09 in 50% DMF solution. Examination of ¹³C-NMR spectra provided convincing evidence for the formation of statistical copolymers. Copolymerizations richer in MAA provided copolymers of higher molecular weights.