Determination of Negative Binding Sites on Hair Surfaces UsingXPS and Ba2+ Labeling

Abstract

The affinity for adsorption of cationic conditioning polymers and organics to hair fiber surfaces is largely determined by the concentration of negative sites on the hair surface. In this study, XPS and Ba 2+ labeling were used to determine the negative site concentration on brown and bleached hair samples. Differences in negative site concentration were determined for each hair type as well as along the length of the hair fibers from root to tip end. The middle and root sections of the bleached hair exhibited a higher negative site concentration than the brown hair. The negative site concentration increased from root to tip for the brown hair, but decreased from root to tip for the bleached hair. Differences in negative site concentration between hair samples were correlated with variations in the RSO 3 - concentrations on the fiber surfaces. Barium ion uptake in addition to that associated with RSO 3 - was attributed to carboxyl site adsorption or to Ba(OH) 2 entrapment within the pores of the hair fiber. Angle-resolved XPS measurements suggested that Ba 2+ ions at the outer surface of the fibers were bonded to two negative surface sites, in agreement with theory. Barium ions in the subsurface region of the fibers may be bonded to only one negative site or may be present as entrapped Ba(OH) 2 .