INTERACTIONS BETWEEN POLYANION-POLYCATION SYSTEMS AND KAOLIN

The phase behavior of the polyanion-polycation system, consisting of a branched polyethylene imine and a sodium salt of polyacrylic acid, wa s investigated as a function of the polymer concentration. At low poly mer concentrations a small area of initial phase separation was observ ed, surrounded by a homogeneous one-phase system. The homogeneous, con centrated polyanion-polycation systems were characterized viscometrica lly, densitometrically, and spectroscopically. Under special mixing co nditions, a significant viscosity enhancement was observed due to Coul ombic interactions between the oppositely charged polyelectrolyte comp onents. The interactions of the polyelectrolyte components with kaolin were investigated separately in the concentration range of initial ph ase separation as well as in the area of concentrated, optically clear polyanionpolycation systems. In the concentration range of phase sepa ration polyanion-polycation interactions are dominant with regard to p olyelectrolyte-kaolin interactions. When adding concentrated homogeneo us polyanion-polycation systems to concentrated kaolin dispersions abo ve a critical polyelectrolyte concentration, a transition to polyelect rolyte-kaolin pastes was observed. In general, these results are of pr actical importance for a better understanding of structuring phenomena in pigment systems. (C) 1994 Academic Press, Inc.