Smectite-polymer interactions in aqueous systems

Abstract

AbstractNeutron scattering studies have indicated that the non-coordinated water at smectite surfaces has a similar mobility to that of bulk water, but that the water coordinated to the cations is immobile on the time scale of the neutron measurements. Thus hydrophylic polymers can readily displace the non-coordinated water and bind to the silicate surface, and to the exchangeable cations through a water-bridge mechanism. Poly(ethylene oxide) molecules with molecular weights up to 4000 appear to be bound to Na-montmorillonite in flattened conformations at the clay surface. Poly(vinyl alcohol) is extensively bound by Na-montmorillonite and by Na-Laponite (a synthetic hectorite-like clay); as binding progresses fewer molecule segments can contact the surface and so at the higher levels of adsorption extensive loops of polymer extend away from the silicate surface. Some polyanions provide good protection for smectites against flocculation with salt. The abilities of such polymers to protect the clays is dependent both on the extents of the charges and on the solution conformations which these polymers can assume.