The kinetics of batch aqueous-phase solution radical copolymerization of an ionizable monomer acrylic acid (AA) with a cationic monomer 2-(methacryloyloxyethyl)trimethylammonium chloride (TMAEMC) to produce polyelectrolytes is investigated using in situ NMR to follow both overall monomer conversion and comonomer composition. The rate of monomer consumption was dependent on the initial weight fraction of monomer, varied between 0.05 and 0.40, and initial comonomer composition. The unreacted monomer is depleted in TMAEMC with increasing conversion for polymerizations conducted with an initial TMAEMC molar fraction of less than 90%. AA was preferentially incorporated above this level, with the azeotropic behavior dependent on the total monomer concentration in the aqueous solution. Semibatch copolymerizations demonstrate that a constant copolymer composition can be obtained Under specific experimental conditions. A model of AA-TMAEMC copolymerization is formulated that predicts polymerization rates and average polymer molar masses, as well as captures the influence of counterion concentration on copolymer composition.