SynopsisThe effect of ionization (a) and added salts (NaCl, CaC12, MgC12) on the dimensions of commercially available high-molecular-weight polyacrylamides (aw N 4 X 1@), hydrolyzed at various extents (0.04 < T < 0.49) and which have been characterized, was investigated by viscosity and light-scattering measurements performed at 25OC. The data point with evidence to the strong dependence of the chain dimensions on the charge density ( a~) 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 (T > 0.45) in media containing large amounts of salts that lead to precipitation of polymers, especially in the presence of divalent ions.Ed., Plenum, New York, 1973, pp. 105-126. 213-225.

Potentiometric titrations in water of high‐molecular‐weight partly hydrolyzed polyacrylamides were analyzed by the Lifson—Katchalsky rodlike model. A fair concordance was found between theory and experimental curves with pK0 of acid functions of about 4.75 when 0 < τ < 0.49. Two methods were derived to calculate the parameter n of the extended Henderson‐Hasselbach equation by using a series expansion of pKa vs. α, not yet reported in the literature. A new equation for n was established and comparison between two sets of values of n, obtained by using the theoretical ΔpK curves and series expansion is discussed.

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