Viscosities of poly(N-vinylacetamide) solutions in the presence of salts, urea and guanidine hydrochloride

Summary

In the aqueous solutions of poly(N-vinylacetamide) in the presence of Na₂SO₄ or (NH₄)₂SO₄, the intrinsic viscosities were small and the Huggins constants were large compared with those in water. Similar but much less effects were observed for NaF. Opposite effects were found, however, for NaSCN. The poor solvent quality of aqueous sulfate solutions was significantly improved by the addition of guanidine hydrochloride to 3 M or higher. Urea was much less effective in improving the solvent quality. The different effects observed between urea and GdnHCl may be explained by their different binding affinities to amide group. Solubilization of PNVA flocculates induced by the presence of 0.8 M Na₂SO₄ took place by adding urea to 1 M, although only small changes were detected in the viscosity behavior accompanying the addition of 1 M urea.