Transesterification or polymerization? Reaction mechanism and kinetics of 2-(diethylamino)ethyl methacrylate with methanol and the competitive effect on free-radical polymerization

Abstract

Transesterification of 2-(diethylamino)ethyl methacrylate (DEAEMA) with methanol leads to the formation of methyl methacrylate (MMA) and 2-(diethylamino)ethanol; this alcoholysis reaction is studied by Density Functional Theory (DFT) calculations and in situ¹H-NMR measurements. The transesterification mechanism involves the cooperative effect of methanol. Second-order transesterification kinetics and Arrhenius parameters (A and E_a) are reported. Furthermore, the competition between transesterification and (co)polymerization between DEAEMA and the MMA transesterification product, using 2,2-azobis (2-methylpropionitrile) (AIBN) as an initiator at 70 °C, has been analysed. In experiments with a DEAEMA : methanol molar ratio of 1 : 46 the copolymerization results in a large proportion of the MMA copolymer composition (F_MMA) of 60 mol%; with an equimolar ratio the transesterification is avoided and the F_MMA is only 2 mol%. F_MMA can also be tuned by modification of the DEAEMA : AIBN molar ratio. Therefore, this work provides guidelines for the synthesis of well-defined poly(DEAEMA) and poly(DEAEMA-co-MMA) in primary alcohols.