Clusters of Optimum Size Formed by Hydrophobically Associating Polyelectrolyte in Homogeneous Solutions and in Supernatant Phase in Equilibrium with Macroscopic Physical Gel

Summary: 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. Schematic representation of the formation of supramolecular structures in aqueous solutions of hydrophobically associative polyelectrolyte. magnified image Schematic representation of the formation of supramolecular structures in aqueous solutions of hydrophobically associative polyelectrolyte.