An In-Situ NMR Study of Radical Copolymerization Kinetics of Acrylamide and Non-Ionized Acrylic Acid in Aqueous Solution

An in-situ NMR technique has been developed to study the aqueous phase copolymerization of non-ionized acrylic acid (AA) and acrylamide (AM) under near-isothermal conditions at much higher monomer contents than previously reported in the literature. The composition data obtained over the entire conversion range provides a precise estimate of monomer reactivity ratios not available from low conversion data. The set of experiments, with initial monomer content in aqueous solution varied between 5 and 40%, were well-fit over the complete conversion range by r(AA) = 1.24 +/- 0.02, and r(AM) = 0.55 +/- 0.01. It was found that the rate of monomer conversion increases with increasing monomer concentration, a trend contrary to the known decrease in the AA and AM chain-end propagation rate coefficients.