High‐molecular‐weight hydrolyzed polyacrylamides. I. Characterization. Effect of salts on the conformational properties

The effect of ionization (α) and added salts (NaCl, CaCl 2 , MgCl 2 ) on the dimensions of commercially available high‐molecular‐weight polyacrylamides ( M w ≃ 4 × 10 6 ), hydrolyzed at various extents (0.04 < τ < 0.49) and which have been characterized, was investigated by viscosity and light‐scattering measurements performed at 25°C. The data point with evidence to the strong dependence of the chain dimensions on the charge density (ατ) and the effect of the nature and concentration of added salts. From a practical point of view it is shown that there is no advantage to using too highly hydrolyzed samples (τ > 0.45) in media containing large amounts of salts that lead to precipitation of polymers, especially in the presence of divalent ions.