Acrylate–methacrylate radical copolymerization kinetics of sparingly water-soluble monomers in polar and nonpolar solvents†

Abstract

The properties of waterborne polymer dispersions synthesized by emulsion radical polymerization are influenced by reactions in both the aqueous medium and the growing particles. Mathematical models representing the process often do not consider the difference in the propagation rate coefficient (k_p) of monomers in the two phases, despite the body of evidence demonstrating that solvent polarity influences monomer–monomer and monomer-solvent hydrogen-bonding that affects both k_p homopropagation values and copolymerization reactivity ratios. Therefore, it is vital to develop experimental approaches to systematically measure the influence of solvent on the copolymerization kinetics of hydrophobic monomers under conditions that are similar to emulsion systems. In this work, we study the copolymerization of methyl acrylate (MA) with di(ethylene glycol) methyl ether methacrylate (DEGMEMA) as models for the common emulsion monomers butyl acrylate and methyl methacrylate. As well as varying solvent choice and monomer concentration, MA/DEGMEMA copolymerization kinetics are compared to those of MA with methacrylic acid (MAA) to determine the influence of monomer functionality on its relative reactivity. The findings suggest that the copolymer composition of all methacrylate–acrylate systems – whether involving functional or non-functional monomers – converge to a single curve in protic polar aqueous solution.