Effect of concentration regime on rheological properties of sodium polymethacrylate and its complexes with polystyrene-poly(N-ethyl-4-vinylpyridinium bromide) block copolymer in aqueous salt solution

The effect of concentration on the behavior of high-molecular-mass sodium polymethacrylate (M _w = 3.9 × 10⁵) in a 0.1 M NaCl aqueous solution was studied by the methods of dynamic and static light scattering, and capillary and rotational viscometry. It was shown that the concentration corresponding to the formation of fluctuation network of polyelectrolyte entanglements (6.4%) is substantially higher than the crossover concentration (0.25%). This fact indicates the existence of a wide concentration interval for a semidilute unentangled polyanion solution. The introduction of minor amounts of micelles of cationic amphiphilic polystyrene-poly(N-ethyl-4-vinylpyridinium bromide) diblock copolymer is accompanied by the development of the network of an interpolyelectrolyte complex. The junctions of this network are diblock copolymer micelles that are linked to polyanion macromolecules via salt bonds. The formation of interpolyelectrolyte network leads to the additional structuring of the sodium polymethacrylate solution and an increase in its viscosity. The growth in viscosity is most pronounced in the concentration region above the concentration corresponding to the formation of entanglement network of the free polyanion.