Water‐soluble copolymers. VI. Dilute solution viscosity studies of random copolymers of acrylamide with sulfonated comonomers

Dilute solution viscosity of a series of random copolymers of acrylamide (AM) with sodium‐2‐acrylamido‐2‐methylpropane sulfonate (NaAMPS) and with sodium‐2‐sulfoethylmethacrylate (NaSEM) has been studied using a four‐bulb shear dilution capillary viscometer. The hydrodynamic volume of the copolymers in aqueous media was determined as a function of salt concentration, temperature, shear rate, and time. A linear relationship was observed between the intrinsic viscosity [η] 0 and the reciprocal of the square root of ionic strength in sodium chloride solutions, with salt concentrations varying from 0.043 M to 0.257 M . Negative temperature coefficients for [η] 0 indicate a decrease in the hydrodynamic volume of the ionic polymer molecules with increasing temperature. The relative zero‐shear‐intrinsic‐viscosity change in distilled water to 0.257 M sodium chloride aqueous media is used to elucidate viscosity–structure relationships. A maximum value is reached for this parameter at a composition of about 30 mol % of ionic comonomers for AM–NaAMPS and AM–NaSEM copolymer series.