76 JOURNAL OF COSMETIC SCIENCE Figure 10. (a) 25 Kx magnification SEM image of bleached hair fiber surface. (b) 25 Kx magnification SEM image of treated hair fiber surface.

HAIR SURFACE CHEMISTRY 77 1 % N and 12.3% Si. From this result it is evident that a homogeneously mixed overlayer of the diester quat and dimethicone can not be present on the surface. The observed Si concentration on the treated sample is 12. 5 % indicating that all of the observed signal would need to come from such a mixed overlayer in order to achieve this Si content. Clearly however, there is signal still originating from the substrate hair in the form of S, peptide N and Ca. In addition the nitrogen level (as quat) is too high so the quat either needs to be present in lesser quantity or itself attenuated. The more likely situation is that the quat is more closely associated with the hair surface and the dimethicone is on top of the quat. This is a more appealing situation for the following reasons: 1. The surface spectroscopic compositional data are more in keeping with a segregated layer structure. 2. The polar quat group is known to preferentially interact with the polar hair fiber surface, specifically the surface sulfonate groups. 3. Surface free energy would be minimized by having the silicone at the hair exterior. CONCLUSIONS Through the illustrations provided in this paper the value of direct spectroscopic in­ vestigation of fiber surface chemistry is demonstrated. Combined with the morphologi­ cal information available from modern SEM, a thorough description of treatment effects can be gathered. XPS data clearly show chemical effect resulting from bleaching and conditioning treat­ ments. Bleaching effects resulted in the removal of a hydrocarbon overlayer and the oxidation of surface functional groups. Increasing time, pH or the addition of surfactant were all seen to enhance the ability of the peroxide to chemically alter the hair fiber surface. Absorption of conditioning molecules onto the hair fiber can be measured by the presence of unique elemental or chemical states. Estimations of overlayer thickness and structure can be made based on the surface sensitive data. REFERENCES (1) J. Alan Swift, "Fundamentals of Human Hair Science" (Michelle Press, Dorset, England, 1997). (2) C.R. Robbins, "Chemical and Physical Behavior of Human Hair" (Springer-Verlag, New York, 1988). (3) M. M. Millard, Anal. Chem., 44, 828 (1972). (4) B. C. Beard and J. Hare,]. Surfact. Deterg., 5, 145 (2002). (5) Michael A. Stranick, Surf Interface Anal., 24, 522 (1996). (6) S. Tanuma, C. J. Powell, and D.R. Penn, Surf Interface Anal., 21, 165 (1993). (7) J. H. Scofield,]. Electron Spec. Rel. Phen., 8, 129 (1976).