WATER-SOLUBLE COPOLYMERS .43. AMPHOLYTIC COPOLYMERS OF SODIUM 2-(ACRYLAMIDO)-2-METHYLPROPANESULFONATE WITH [2-(ACRYLAMIDO)-2-METHYLPROPYL]TRIMETHYLAMMONIUM CHLORIDE

Copolymers of sodium 2-(acrylamido)-2-methylpropanesulfonate (NaAMPS) with [2-(acrylamido)-2-methylpropyl]trimethylammonium chloride (AMPTAC) have been prepared by free-radical polymerization in a 0.5 M NaCl aqueous solution using potassium persulfate as the initiator. Copolymer compositions were obtained by C-13 NMR and elemental analysis. An r1r2 value of 0.31 indicates an alternating microstructure for NaAMPS and AMPTAC monomer units. Molecular weights, second virial coefficients, diffusion coefficients, and average diameters were found using classical and quasielastic low-angle laser light scattering. As the compositions of the copolymers approach equal molar concentrations of NaAMPS and AMPTAC, polyampholyte behavior is observed. The second virial coefficients can be used to distinguish the polyelectrolyte/polyampholyte transition as a function of copolymer composition. The dilute-solution properties of the copolymers, as well as those of the NaAMPS and AMPTAC homopolymers, have been studied as related to composition, pH, temperature, and added electrolytes.