18-MEA DEPOSITION ON HAIR 43 hydrophobic part to the air interface. Therefore, it seems reasonable that 18-MEA/SPDA could provide persistent hydrophobicity to the alkaline-color-treated weathered hair surface. CONCLUSIONS The main conclusions are as follows: 1. The application of a combination of 18-MEA with relatively hydrophobic tertiary amines (DSDA or SPDA) made damaged hair surfaces hydrophobic, and the hydro- phobicity was maintained ever after one instance of shampooing with a plain shampoo [15 wt% of sodium polyoxyethylene lauryl ether sulfate (2.5 E.O.) with 2 wt% N,N- bis(2-hydroxyethyl)-dodecanamide solution adjusted to pH 7 with phosphoric acid]. 2. AFM and ARXPS analysis revealed that 18-MEA/SPDA attaches to a mica surface and forms a layer with high wear resistance, with the alkyl chain (hydrophobic moiety) oriented at an angle of around 25° to the air interface. We believe this attachment and orientation could be similar in human hair. 3. The mechanism of sustainable hydrophobicity of the hair surfaces generated by 18- MEA/SPDA has some characteristics in common with the natural 18-MEA layer formed on untreated healthy hair, including being about 1 nm in thickness, having the hydrophilic area of molecules binding tightly to the surface, and orienting its hydrophobic part to the air interface. ACKNOWLEDGMENTS The authors express their sincere thanks to Mr. Hiroyuki Saijo, Dr. Yoshinori Masukawa, and Mr. Masayuki Okamoto of Kao Corporation for their helpful and fruitful discussions for this study. Our sincere thanks are also due to Dr. Osamu Yamashita of Kao Corpora- tion for this technical support in the logP calculations. REFERENCES (1) D. J. Evans, J. D. Leeder, J. A. Rippon, and D. E. Rivett, Separation and analysis of the surface lipids of the wool fi ber, Proc. 7th Int. Wool Text. Res. Conf., Tokyo, Japan, I, 135–142 (1985). (2) P. W. Wertz and D. T. Dowing, Integral lipids of human hair, Lipids, 23, 878–881 (1988). (3) P. W. Wertz and D. T. Dowing, Integral lipids of mammalian hair, Comp. Biochem. Physiol., 92B, 759– 761 (1989). (4) A. P. Negri, H. J. Cornell, and D. E. Rivett, The nature of covalently bound fatty acids in wool fi bers, Aust. J. Agric. Res., 42, 1285–1292 (1991). (5) A. P. Negri, H. J. Cornell, and D. E. Rivett, Effects of proceeding on the bound and free fatty acid levels in wool, Text. Res. J., 62, 381–387 (1992). (6) S. Naito, M. Ooshika, N. Yorimoto, and Y. Kuroda, The structure of bound lipids of human hair fi bers and its physical properties, Proc. 9th Int. Wool Text. Res. Conf., Biella, Italy, II, 367–374 (1996). (7) D. J. Evans and M. Lanczki, Cleavage of integral surface lipids of wool by aminolysis, Textile Res. J., 67, 435–444 (1997). (8) U. Kalkbrenner, H. Koener, H. Hoecker, and D. E. Rivett, Studies on the composition of the wool cuticle, Proc. 8th Int. Wool Text. Res. Conf., Christuchurch, New Zealand, I, 398–407 (1990). (9) C. M. Carr, I. H. Leaver, and A. E. Hughes, X-ray photoelectron spectroscopic study of the wool fi ber surface, Textile Res. J., 56, 457 (1986).

JOURNAL OF COSMETIC SCIENCE 44 (10) S. Breakspear, J. R. Smith, and G. Luengo, Effect of the covalently linked fatty acid 18-MEA on the nanotribology of hair’s outermost surface, J. Struct. Biol., 149, 235–242 (2005). (11) C. A. Torre, B. Bhusham, J.-Z. Yang, and P. M. Torgerson, Nanotribological effects of silicone type, silicone deposition level, and surfactant type on human hair using atomic force microscopy, J. Cosmet. Sci., 57, 37–56 (2006). (12) L. N. Jones and D. E. Rivett, The role of 18-methyleicosanoic acid in the structure and formation of mammalian hair fi bre, Micron, 28, 469–485 (1997). (13) J. A. Swift, Human hair cuticle: Biologically conspired to the owner’s advantage, J. Cosmet. Sci., 50, 23–47 (1999). (14) M. Yasuda, J. Hair Sci., 95, 7–12 (2004). (15) M. L. Tate, Y. K. Kamath, S. B. Ruetsch, and H.-D. Weigmann, Quantifi cation and prevention of hair damage, J. Sci. Cosmet. Chem., 44, 347–371 (1993). (16) Kao Corporation patents, JP1925274, EP0483689, US5476649. (17) Kao Corporation patent, US6576794 B2. (18) A. P. Negri, H. J. Cornell, and D. E. Rivett, A model for the surface of keratin fi bers, Textile Res. J., 63, 109–115 (1993). (19) H. Zahn, H. Messinger, and H. Hoecker, Covalently linked fatty acids at the surface of wool: Part of the “cuticle cell envelope,” Text. Res. J., 64, 554–555 (1994). (20) R. J. Ward, H. A. Willis, G. A. George, G. B. Guise, R. J. Denning, D. J. Evans, and R. D. Short, Surface analysis of wool by X-ray photoelectron spectroscopy and static secondary ion mass spectroscopy, Text. Res. J., 63, 362–368 (1993).