Correlation between adsorption and the effects of surfactants and polymers on hair

The external horny layer of the hair, the cuticula, consists largely of amorphous keratin, which, in young undamaged hairs, contains only a few polar groups and is hydrophobic. External influences such as sunshine, permanent waving or bleaching lead to the formation of polar groups in the cuticula that hydrophilize the hair surface. Surfactants or polymers in hair care products are adsorbed on the hair and alter its wetting characteristics; this can be followed very sensitively by means of Wilhelmy’s method. Cationic surfactants used to lubricate the hair are adsorbed in several layers on the hair surface. After the outer layers have been rinsed and desorbed in water, a single layer remains attached, whose hydrophobic hydrocarbon chains are oriented towards the aqueous phase. Cationic polymers are also adsorbed from aqueous solutions and solutions containing anionic surfactants, but in this case, however, the surface is hydrophilized. Parallel studies of combability were carried out, and showed that the reduced friction associated with cationic surfactants is a consequence of the presence of the hydrophobizing adsorption film.