Surface forces measurements on a cationic polymer in the presence of an anionic surfactantl

Surface forces measurements have been made between adsorbed layers on mica of a cationic polymer (Polymer JR-400) in distilled water, both in the absence and in the presence of the anionic surfactant sodium dodecylsulfate. In the absence of surfactant, the polymer was bound to the oppositely charged mica surface and exhibited hysteresis force curves which were monotonically repulsive up to a compression of 10apNm-1. In the presence of surfactant hysteresis was also observed but while the compressing force curves were monotonically repulsive, the separating force curves showed a significant attraction between the layers. This suggests that bound surfactant may be inducing hydrophobic interactions between the adsorbed layers.