Clusters of optimum size formed by hydrophobically associating polyelectrolyte in homogeneous solutions and in supernatant phase in equilibrium with macroscopic physical gel

The formation of finite-sized microgel particles was revealed by photon correlation spectroscopy in aqueous solutions of hydrophobically associative polyelectrolyte polystyrene-block-poly(sodium methacrylate)-block-polystyrene. Starting from the lowest polymer concentration (1 × 10^-6 g· L^-1) up to 1 g·L^-1 a single relaxation process dominates the spectrum of relaxation times of the polymer solutions. This dominant mode was attributed to the diffusive motion of supramolecular microgel particles with a size of about 100 nm. Above a polyelectrolyte concentration of 1.0 g·L^-1, the size of the microgel grows up to ca. 300 nm. At a polymer concentration 20 g·L^-1, macroscopic phase separation occurs: the liquid phase of the microgel-cluster solution coexists with the phase of the macroscopic gel. (Figure Presented) Schematic representation of the formation of supramolecular structures in aqueous solutions of hydrophobically associative polyelectrolyte.