Mechanistic study on polymerization of acrylamide induced by methyl ethyl ketone and its derivatives based on the interaction between carbonyl and amide groups

Abstract

Polymerizations of acrylamide (AAm) were carried out in the presence of methyl ethyl ketone (MEK), methyl isopropyl ketone (MIK) and t-butyl methyl ketone (tBMK) in tetrahydrofuran at 30°C. It was found that the rate of polymerization (R_p) increased according to this order: MEK < MIK < tBMK in the case of AAm, but in the methyl methacrylate (MMA) system the order was as followed: MEK > MIK > tBMK. The maximum value of R_p for AAm reached the point of equimolar ratio of AAm to ketone in any of the three systems. The polymerization was confirmed to proceed through radical mechanism. Effects of temperature on the R_p were discussed in a temperature range of 30–60°C. The overall activation energy (E_a) was estimated to be 52.6, 35.7, and 22.7 KJ/mol for MEK, MIK, and tBMK, respectively. No acceleration of the polymerization of N,N-dimethylacrylamide system was observed even in the presence of these ketones. The participation of –NH₂ in the complexation of monomer with the ketones is proposed in the initiation of this radical polymerization.