8 JOURNAL OF THE SOCIETY OF COSMETIC CHEMISTS Table I Amount of Surfactant Ad(b)sorbed by Reduced Hair Treated at pH 10.7 Amount ad(b)sorbed Compound Time (hours) (mg/g) 11 0.5 33.78 12 0.5 37.73 13 0.5 19.26 that the deposited isothiuronium-containing quaternary salt does not penetrate deeply into the fiber structure and that most of it does not form covalent bonds with keratin. CONDITIONING EFFECTS The ability of 1ong-alkyl-chain quaternary ammonium salts to improve dry and wet combability of hair is well known and has been previously described in the literature (17). Low-molecular-weight quat treatments such as cream rinses are, however, not durable, since the adsorbed surfactant can sometimes be removed by shampooing. We expected that the incorporation of a reactive moiety into the surfactant structure might result in covalent binding of a surfactant to keratin, and therefore improve the dura- bility of the conditioning effect. Wet combing measurements, obtained following the treatments with a series of com- pounds 5-10, and after four and eight shampooings, were used to assess the condi- tioning effect. The treatments were performed at pH 5.3 (unhydrolyzed isothiuronium salt) and pH 10.7 (partially hydrolyzed isothiuronium salt). Stearalkonium chloride, a widely used cationic surfactant in cream rinse formulations, was also tested as a control. Table III shows the wet combing data obtained for the experiments performed on un- modified hair. For the control (untreated tresses) the wet combing work was found to increase after four and eight shampooings. This phenomenon is not well understood, although it may be caused by the progressive damage to the hair cuticle caused by shampooing, combing, and handling in the wet state (18). The treatment with the unreactive surfactant, stearalkonium chloride, reduced the wet combing work both at pH 5.3 and 10.7. The surfactant is not completely removed from the fibers after eight shampooings as evidenced by the reduced values of combing work as compared to the untreated control. Note that the value of the combing work obtained immediately after Table II Quantity of Surfactant Removed From Unmodified Hair Treated at pH 5.3 or 10.7 Amount desorbed (mg/g) pH of the Compound Treatment After 2 hours After 72 hours 11 5.3 2.76 10.7 2.54 12 5.3 5.84 10.7 5.61 13 5.3 5.19 10.7 3.98 3.72 (11.4%) 5.48 (16.0%) 6.86 (21.1%) 7.05 (20.7%) 6.26 (80.7%) 6.57 (41.3%)

DYES AND SURFACTANTS FOR HAIR 9 Table III Results of Wet Combing Work on Intact Hair Wet combing work (g/cm) pH of the After After After Treatment (30 min) Treatment treatment 4 shampoos 8 shampoos Control 5.3 952 3006 2941 10.7 1114 1855 3270 Stea•lkonium chloride 5.3 715 1078 1704 10.7 888 640 1504 Compound 5 5.3 697 962 1804 10.7 1282 660 1573 Compound 6 5.3 688 986 1878 10.7 1222 1068 1542 Compound 7 5.3 719 594 1108 10.7 1004 340 708 Compound 8 5.3 722 1162 1872 10.7 1091 666 1918 Compound 9 5.3 785 846 1744 10.7 1038 553 2384 Compound 10 5.3 552 630 1074 10.7 303 207 582 the treatment at pH 10.7 is higher than that for the tresses subjected to four sham- pooings. This might be caused by the enhanced absorption of the surfactant at this pH, which may lead to less adsorption, and consequently, less surface modification. Subse- quent shampooing of the hair results in a decrease of combing work values, probably because of diffusion to the surface and formation of surface hemimicelles of the absorbed surfactant. This and alternative mechanisms are discussed further in the text of this paper. An additional four shampooings produce an increase in combing forces, due to removal of the quats from the surface. Similar combing characteristics are displayed by the hydroxyl- and bromide-containing cationic surfactants. In both cases, treatments at pH 10.7 resulted in relatively high combing work, which was subsequently reduced by four shampooings. Also, no qualitative difference in performance was observed for sur- factants with one and two hydroxyl or bromide groups. Both isothiuronium-containing quats were considerably more effective in reducing the combing work than the nonreactive surfactants, especially when applied at high pH. The conditioning effect was also more durable, and clearly evident after eight sham- pooings. The data presented in Table III also indicate that the surfactant containing two isothiuronium groups (compound 10) produces a more significant reduction in combing forces than its monoisothiuronium analog. The combing work measurements obtained for the treatments performed on reduced hair are presented in Table IV. According to the ad(b)sorption data, under these condi- tions the cationic surfactants diffuse into hair fibers at a high rate. Consequently, signif- icant and durable improvements in combing were observed for stearalkonium chloride and the hydroxyl-containing surfactants. The reduced hair treated with bromide-con-