Abstract
The binding isotherms of a cationic surfactant of a long alkyl chain, stearyltrimethylammonium chloride, to three types of human hair (unaltered, bleached, and permanent-waved) were obtained and analyzed. The isotherms showed a Langmuir-type binding, from which the binding constant, the number of binding sites in saturation, and thermodynamic parameters were calculated. The binding mechanism is discussed from the point of view of hydrophobic and electrostatic interactions, and the location of binding sites estimated by a surface analysis of the hairs by X-ray photoelectron spectroscopy (XPS).
