7 4 JOURNAL OF COSMETIC SCIENCE N(E) Min: 52 Max: 48329 0(1s) C(1s) N(1 s) Si(2s) Si(2p) �-�1L� 602 541.8 481.6 421.4 361.2 301 240.8 180.6 120.4 60.2 -4.57764e-005 Binding Energy (eV) Figure 8. Surface elemental "survey" scan showing the composition of conditioner-treated hair. Element C N 0 s Si Ca Table III Surface Composition of Conditioner-Treated and Bleached Hair Bleached sample 73.2 7.7 15.9 1.9 0.5 0.8 Treated sample 64.8 2.0 19.0 1.5 12.5 0.1 and ester quat. The changes in the C(ls) spectrum indicate the presence of a predomi­ nantly hydrocarbon like layer at the surface, which in this case is due to the methyl groups of the dimethicone and the long change fatty acid esters in the ester quat (Figure 9). High-resolution spectra from the treated surface confirm the presence of the ester quat by the unique R4N + chemical state of nitrogen. The relatively high oxygen content of the ester quat (-9 atom% oxygen) and especially the dimethicone (-23 atom% oxygen) are responsible for increasing the observed oxygen content on the treated hair surface. No evidence for retained chloride (Cl-) from the original salt of the quaternary amine was observed. The absence of the anionic chloride at the surface indicates the solvated chloride did not interact with the hair surface, (hair surface possesses a net negative charge at neutral pH, IEP = 3.7) and was washed away with the rinse. In addition, the absence of negatively charged counter ion indicates that multilayer formation of the quat

C ::::, 0 0 C 0 J: � � 292 . , .. ' 290 HAIR SURFACE CHEMISTRY I-+- Bleached -- Test Formulation I 288 286 Binding Energy, eV 284 282 Figure 9. Overlay of C(ls) spectra from bleached and conditioner-treated hair. 75 a 280 through alkyl tail association did not occur. This observation does however beg the question of surface charge balance with regard to the positively charge quaternary ammonium group. As noted in an earlier publication (4), the quaternary amine groups have a strong binding preference for the surface sulfonate groups, which for their part carry a negative charge. Surface topographic structure as revealed by the SEM indicates a smoothening of the cuticle plateaus after conditioning. Comparison between the bleached and conditioned surfaces at 10 Kx shows this effect (Figure 10 a,b). Indeed this visual result is exactly what one typically associates with the function of a hair conditioner: smoothness, uni­ formity, and repair. Together the spectroscopy and these images demonstrate the over­ layer nature of the conditioning treatment. DISCUSSION The structure of the surface film resulting from the conditioning treatment may be explored in light of it composition and attenuation behavior of the hair fiber substrate. The high concentration of Si at the surface (12.5 atom %) is clearly due to the presence of dimethicone, which also accounts in part for the high oxygen. Of the 2% nitrogen observed at the conditioner treated surface 0.5% is contributed by the characteristic N + chemical state of the quat. Using the compositional information of the surface a homo­ geneous mix of the quat and dimethicone can be calculated to give this composition. For every one molecule of quat there would be one silicone polymer with 25 Si atoms. From this relationship an elemental empirical formula can be calculated for the mixture that would represent the mixed overlayer. The composition would be 70.3% C, 16.4% 0,