SynopsisThe effect of temperature (lOO°C) and heating time (up to 384 hr) on the physicochemical properties of high molecular weight ( M p N 4 X lo6) partly hydrolyzed (7 = 31%) polyacrylamide (HPAM-25) solutions with initial pH values near 4 and 7, respectively, is reported. Potentiometric and spectroscopy data indicate that upon heating the solutions for 16 days the extent of hydrolysis is increased up to around 90%. The viscosity behavior, especially in the presence of bivalent salt (CaC12), can be explained by taking such an increase in hydrolysis into consideration. From light scattering data, it is shown that the conformational changes are not correlated with molecular weight degradation.

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.

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