546 JOURNAL OF THE SOCIETY OF COSMETIC CHEMISTS Figure 6. Micrograph of 3000 X of bleached hair, representative of clean hair and hair washed 5 times in low depositing shampoos Figure 7. Micrograph of bleached hair, after 5-cycle shampooing with Polymer JR and potassium laurate

ADSORPTION OF POLYMER JR STRATUM CORNEUM 547 2øø I FETAL PIG / e 0 5 10 TIME(days} Figure 8. Adsorption of Polymer JR-125 on mammalian stratum corneum 15 weight basis, the amount adsorbed is considerably larger than for bleached hair, reaching over 10 per cent for both animal substrates. Like the results for hair, these data are consistent with a mechanism involv- ing slow penetration of the substrate by the polymer. Existing data in the lit- erature support this interpretation. For example, Harrold and Pethica found that large amounts of anionic surfactant could be taken up by powdered epi- dermal keratin (7) while Choman (8) showed that very appreciable swelling occurs in calfskin exposed to anionic surfactant-an indication of penetration by the surfactant. Only qualitative data seem to be available for cationic sur- factants (9, 10) these species are very quickly and tightly bound to skin. The only work specifically on polymer adsorption known to us is that of Cooper- man (11), who determined the substantivity of protein hydrolyzates to hu- man stratum corneum by in vivo and in vitro methods. The polymers used were in the molecular weight range 1000 to 10,000. Kinetics were not fol- lowed, but considerable adsorption occurred in 10 min, and it was shown by stripping experiments that the polymers penetrated well into the skin. The magnitude of deposition on skin suggests that a beneficial effect might be obtained by a barrier or coagulation effect, for example, against penetrat- ing surfactants. We have, in fact, obtained some qualitative visual evidence