Solvent Effect on the Radical Copolymerization of N-Methyl- and N,N-Dimethylacrylamides and N-Methylmethacrylamide with Methyl Methacrylate

Abstract

Solvent effect on radical copolymerizations of N-methylacrylamide (AA) and N-methylmethacrylamide (MA) with methyl methacrylate (MMA, M2) was studied using benzene (BZ), dioxane (DO), acetonitrile (ACN), ethanol (EtOH), and N,N-dimethylformamide (DMF). Spectroscopic studies revealed that the solvents influence these amide monomers (M1) with regards to their association by hydrogen-bonding and dipole–dipole interaction. The solvent ability which makes the self-associations of AA and MA more effective decreases in the order of BZ>DO>ACN>EtOH>DMF. The higher the solvent ability for the self-associations of the amide monomers, the larger the values of r1. The extent of the solvent effect on both the monomers decreased with decreasing order of their self-association tendencies, i.e., AA>MA. M1 concentration around M1. radical is considered to be enhanced by its association with M1 in the solvent with higher ability for the self-association of M1. This enhances the propagation-rate between M1. radical and M1 and increases apparently k11 as compared with k12. The r2 values did not change depending on solvents except the copolymerization in BZ. The interactions between MMA and the amide monomers are too weak to raise their local concentrations around M2. radical. BZ increases extraordinarily r1 and decreases r2, respectively. Copolymers precipitated during copolymerization in BZ are considered to adsorb the amide monomers, since their interactions with BZ are extremely weak. This increases the local M1 concentration around both M1. and M2. radicals. BZ influences even the copolymerization of N,N-dimethylacrylamide which has been considered to be independent of the solvents. Dipole–dipole interaction has been ascribed to this solvent effect.