Viscosimetric behaviour of hydrolyzed polyacrylamide-poly(4-vinylpyridine) [AD37-P4VP] mixture in aqueous solution

The interactions between 27% hydrolyzed polyacrylamide [AD37] and poly(4-vinylpyridine) [P4VP], in aqueous solutions and at neutralization degree α = 1, were studied by using viscosimetry technique. The reduced viscosities of these copolymer mixture solutions, at 25 °C, reach several orders of magnitude higher than the reduced viscosity of each polymer taken separately, and according to the ratio R of the chain numbers. Intermolecular electrostatic associations are favoured by increasing the P4VP concentration corresponding to high R values. Thus, mixtures rich in P4VP are characterized by a high decrease in the viscosity due to interpolymer complete complexation AD37-P4VP, leading to the totally contraction or collapse of the polymer chains. Strongest reduced viscosities, due to the inter-chain AD37 associations, are observed for the mixtures poor in P4VP (so the weakest ratios R of the chain numbers). In order to understand the relative effects of these two polymers on the reduced viscosity, two mixtures containing the same total quantity are compared. Reduced viscosities of each copolymer alone strongly increase by dilution of the aqueous solution. In the case of the mixture, an opposite behaviour is observed with a reduction in the reduced viscosity by dilution. So, the increase of the reduced viscosity according to AD37 concentration, at α constant, shows an intra and an inter-chain associative phenomenon.