Polymer-surfactant interactions studied with the surface force apparatus

The interactions in aqueous media between two adsorbed layers of hydrophobically modified hyforce vs distance profiles have been measured for a nonionic, hydrophobically modified HEC (HMHEC) and a cationic, hydrophobically modified HEC (Quatrisoft). HMHEC, in contrast to the equivalent nonmodified HEC, adsorbs on mica from a 0.1 M NaCl solution. Repulsive forces between mica plates were measured using the surface force apparatus up to a distance of 500 Å. Quatrisoft, as confirmed by XPS measurements, adsorbs strongly from distilled water on mica. Addition of a nonionic surfactant to the cationic polymer results in a marked increase in long range forces, suggesting an expanded polymer-surfactant complex. These data are related to the substantivity to hair and to colloidal stability when combinations of modified cellulosic polymers and nonionic surfactants are used.