Interactions of latex spheres and anionic surfactant in hydrophobically modified polymer aqueous solution

Abstract

The interactions in the system hydrophobically modified hydroxyethylcellulose—anionic surfactant—latex particles in aqueous solution are studied. The existence of a viscosity maximum in the plot of bulk viscosity vs. surfactant concentration was confirmed to be the result of micelle formation. Latex particles of two sizes (radii, 42 and 108 nm) were added at high (1 wt.%) and low (0.016 wt.%) polymer concentrations. At high polymer concentration, it was found that the Stokes—Einstein law fails in the region where micelles are formed. At low polymer concentration, phase separation was observed below the critical micelle concentration of the surfactant. Above this concentration, the diffusion coefficient of latex particles as a function of surfactant concentration was measured. The data were fitted by an exponential function. Using fitted parameters, the dependence of the particle radius on surfactant concentration was established. It was found that the clustering effect occurs only in the case of latex particles of small size (42 nm). For large latex particles, the existence of clusters was not confirmed.