Water‐soluble copolymers. XLV. Ampholytic terpolymers of acrylamide with sodium 3‐acrylamido‐3‐methylbutanoate and 2‐acrylamido‐2‐methylpropanetrimethylammonium chloride

Water‐soluble, low charge density polyampholytes have been synthesized by free‐radical terpolymerization of acrylamide (AM) with sodium 3‐acrylamide‐3‐methylbutanoate (NaAMB) and 2‐acrylamido‐2‐methylpropanetrimethylammonium chloride (AMPTAC). Terpolymer compositions obtained by 13C‐NMR reflect monomer feed concentrations. Molecular weights and second virial coefficients range from 3.43 to 19.4 × 106g/mol and from 1.63 to 3.61 mL mol/g‐2, respectively, as determined by low‐angle laser light scattering. Ionic associations were explored by investigating the dilute solution properties as a function of terpolymer concentration, terpolymer charge density, and added electrolytes. Terpolymers with 0.5, 2.5, and 5.0 mol % of both of the cationic (AMTAC) and anionic (NaAMB) monomers were soluble in deionized water, whereas those with 10 and 15 mol % of each monomer required electrolyte addition. The higher‐density terpolymers undergo a 700% increase in intrinsic viscosity upon changing NaCl concentration from 0.05 to 1M. Polyelectrolyte behavior could be induced by decreasing solution pH below the pKa of the NaAMB mer. Intermolecular ionic associations resulting in gel networks were studied utilizing dynamic mechanical analysis.