Abstract
The rheological behaviour of dilute solutions of a “polyelectrolytic” mixture of polyacrylic acid and PVA in water at a total polymer concentration of 0·5 wt.% has been studied. The relationship between relative viscosity and composition of the polymer mixture has been found, in a number of cases, to exhibit positive deviation from additivity with a maximum close to a composition of 20 wt.% of polyacrylic acid. In order for the effect to appear, the molecular mass of the polyacrylic acid sample should be above a critical value but the molecular mass of the PVA sample can be artitrary. The observed effects are explained by the supposition that non-stoichiometric polyelectrolytic complexes are formed. Application of model concepts, developed here for the supermolecular organization of the complexes, to the analysis of the experimental data has made it possible to conclude that the most probable organization is a randomly branched macromolecule with trifunctional branching nodes.
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