Probe diffusion measurements of polystyrene latex particles in polyelectrolyte solutions of varying ionic strength

Copyright © 2002 American Chemical SocietyThe diffusion of polystyrene latex particles in solutions of a poly(acrylic acid-co-acrylamide) polyelectrolyte as a function of both polyelectrolyte concentration and solution ionic strength has been investigated using dynamic light scattering. Two apparent diffusion coefficients were measured for the latex probe particles in the polyelectrolyte solutions. Designated as Dfast and Dslow, the fast diffusional mode increases to a maximum as a function of polyelectrolyte concentration, with the maximum increasing in magnitude as the ionic strength increases. Dslow decreases as a function of polyelectrolyte concentration in low ionic strength solutions. However, Dslow shows a slight increase with polyelectrolyte concentration in the higher ionic strength solutions. The results are discussed with reference to calculated correlation lengths for the polyelectrolyte solutions and are compared with the data obtained from polymer solutions measured using dynamic light scattering where similar trends have been observed. The latex spheres appear to probe the single chain motion, cooperative diffusion, and the macroscopic diffusional motions, self-diffusion, of the polyelectrolyte molecules.Bremmell, K. E.; Dunstan, D. E

Morphology of adsorbed polymers and solid surface wettability

Copyright © 2005 American Chemical SocietyThe adsorption of a polyacrylamide (MW 14600) and two polysaccharides (MW 9260 and 706 × 103) onto model silica surfaces of different hydrophobicities was investigated. In all cases, adsorption adhered to the Freundlich isotherm, reflecting the heterogeneous character of the solid substrates. The latter strongly influenced the character of the adsorbed polymer, with morphologies from chainlike structures to thin films and patches being observed. Surface roughness, polymer type, and molecular weight also play roles in controlling adsorbed polymer morphology. Surface wettability is strongly influenced by the thickness of the adsorbed layer.Gillian B. Kaggwa, Stefanie Froebe, Le Huynh, John Ralston, and Kristen Bremmel