Influence of Solvents on Acrylate-Methacrylate Copolymerization Chain Growth Kinetics: From Bulk to Dilute Aqueous Solution

Abstract The PLP–SEC technique, i.e., pulsed-laser polymerization coupled with size-exclusion chromatographic analysis of the resulting copolymer molar mass distributions, is used to investigate the effects of solvent polarity (ethanol/water mixtures varying from pure ethanol to pure water) and monomer concentrations (1 wt % to bulk) on composition-averaged propagation rate coefficients (kpcop) at 60 °C for methyl acrylate (MA) copolymerized in solution with di(ethylene glycol) methyl ether methacrylate (DEGMEMA), methacrylic acid (MAA) and methyl methacrylate (MMA), as well as for acrylic acid (AA) copolymerized with DEGMEMA. The kpcop values increase with increasing water content in the alcohol-water solvent mixtures, becoming more than an order of magnitude higher in dilute aqueous solution than in bulk across the full range of comonomer composition. Values for all four systems converge as the solvent environment shifts from bulk (i.e., as in emulsion polymerization particles) to aqueous, despite significant differences in monomer polarity and aqueous solubility between AA vs MA and MAA vs DEGMEMA vs MMA. These profound differences in chain-growth kinetics in bulk and aqueous solution should be accounted for when modeling emulsion copolymerization kinetics.