Influence of Intermolecular Interactions on Acrylate–Methacrylate Copolymerization Reactivity Ratios: From Bulk to Aqueous Solution

The influence of both monomer concentration (1 wt % to bulk) and solvent polarity (ethanol/water mixtures varying from pure ethanol to pure water) on copolymer composition is systematically investigated for the copolymerizations of methyl acrylate (MA) with di(ethylene glycol) methyl ether methacrylate (DEGMEMA), methacrylic acid (MAA), and methyl methacrylate (MMA), as well as for acrylic acid (AA) with DEGMEMA. Nonlinear parameter estimation techniques are employed to estimate system reactivity ratios from in situ nuclear magnetic resonance spectroscopy measurements of comonomer composition drift followed to high conversions as well as from copolymer compositions measured for low-conversion samples produced by pulsed-laser polymerization. The study demonstrates that the reactivity ratios needed to describe copolymerization in polymer particles can differ substantially from those required to accurately represent aqueous-phase reactions in emulsion copolymerization. However, acrylate–methacrylate compositions in aqueous solution are effectively described using a single set of reactivity ratios (racrylate = 0.18 ± 0.02 and rmethacrylate = 4.40 ± 0.30), independent of monomer functionality. The extensive data set provides additional important insights into the complex monomer–monomer, solvent–monomer, and solvent–solvent intermolecular interactions that control the copolymer composition in polar media.