Rheological properties of aqueous solutions of poly-1,2-dimethyl-5-vinylpyridinium methyl sulfate and its copolymers

Rheological properties were studied for aqueous solutions of poly-1,2-dimethyl-5-vinylpyridinium methyl sulfate and its copolymers with acrylonitrile, acrylamide, acrylic, and maleic acids in the concentration range from 1 to 10 g dL^{? 1}, temperature range from 25 to 65°C, and range of velocity gradients from 0.2 to 1.3×10 ³ sec^{? 1}. Majority of the resultant gradient dependences of the solution viscosities had a pattern typical for non-Newtonian liquids. The nature of the second comonomer affected the dynamic viscosity, its concentration, and temperature dependences. However, as the content of the second comonomer in the copolymer increased, the characteristic viscosity as well as the highest Newtonian viscosity decreased. The concentration dependences of viscosity and activation parameters of viscous flow indicate that the fluctuation network, formed in solutions of the polyelectrolytes under consideration, is much looser in comparison with solutions of the nonionic polymers. The strength of the fluctuation network increases under conditions of screening of electrostatic repulsion. The critical concentrations (crossover points) were found to be much higher than the average concentration of monomeric units within the polymeric coil and independent of the degree of polymerization or composition of the copolymer. A combination of donor and acceptor functional groups in the copolymers favors formation of additional intra- and intermolecular bonds; therefore, as the temperature rises, additional unfolding of macrocoils and strengthening of the fluctuation network takes place.