ESCA OF POLYMERS ON HAIR 237 group contained in these polymers can serve as an effective tag. Finally, the cellulosic polymers examined have a much higher oxygen content than the native hair surface. This oxygen is in the form of alcohol/ether linkages, and thus deposition would also be expected to increase significantly the observed C- O fraction in the carbon high-resolu- tion spectrum. TREATMENT WITH CELLULOSIC POLYMERS All of the aforementioned effects are observed upon treatment of the hair with the cationic cellulosic polymers. Table III gives the measured surface compositions of hair which was treated with 0.1% aqueous solutions of Polyquaternium-10 and Polyquater- nium-24, sampling again from the center portion of the treated tress. Deposition is evident from the reduced nitrogen and sulfur levels, with a concurrent increase in the surface oxygen concentration. The high resolution results (Table IV) are consistent with this conclusion. As illustrated in Figure 2, large increases in alcohol/ether carbon func- tionality are observed on these polymer-treated surfaces. This ether/alcohol form of carbon is attributed to the cellulosic backbone and side chain substitution of these polymers. The quaternary nitrogen group contained in these polymers is also readily detected by its characteristic binding energy shift (Figure 3). The large increase in the cellulosic region of the spectra produced by exposure to Poly- quaternium-24 indicates that it is retained to a greater degree than Polyquaternium-10, reflecting interesting differences in the adsorption properties of these two polymers. The binding of Polyquaternium-10 will be occasioned principally by electrostatic forces, and in this case will reflect the areas of negative charge concentration on the hair surface. On the other hand, Polyquaternium-24, in addition to this type of binding, can, by the nature of its hydrophobic groups, attach to the hydrophobic areas of the hair fibers. The combination of these properties in this polymer leads to higher adsorption. While these qualitative statements are of interest, it is important to attempt to deter- mine the degree of polymer surface coverage quantitatively. This can be done in several ways. The simplest approach is to assume a heterogeneous surface coverage with inter- dispersed areas of bare and polymer-covered hair. This assumption is supported by wetting force measurements on Polyquaternium-10 treated hair (6,7). Under these con- ditions, the surface coverage can be determined from the measured C/O ratio since the observed ratio is a linear combination of the contributions of each of the two types of surfaces according to equation 1. Measured (C/O) = X(C/O)poly ' + (1 - X)(C/O)hair (1) Table III Surface Composition of Polymer-Treated Hair Atomic % Treatment C O N S None (control) 76.7 12.8 6.4 2.5 Polyquaternium- 10 79.6 16.2 2.6 0.8 Polyquaternium-24 73.0 21.1 2.8 1.3

238 JOURNAL OF THE SOCIETY OF COSMETIC CHEMISTS Table IV High-Resolution Results: Polymer-Treated Hair Atomic % Carbon Nitrogen Treatment CH C - O C = O Amide N + None (control) 61.6 8.2 6.7 6.4 -- Polyquaternium- 10 51.6 22.6 5.4 1.9 0.68 Polyquaternium-24 42.7 26.9 3.4 2.3 0.50 The (C/O)poly values used in the equation were calculated from the known molecular structures of these materials, while (C/O)hai• was taken from the control data in Table I. This calculation gives a surface coverage of 25% and 66% for the samples treated with Polyquaternium-10 and Polyquaternium-24, respectively. These results are interesting in light of previous work reported in this area. Recent data obtained using a modified Wilhelmy balance technique to determine wetting forces on individual hair fibers (6,7) showed an inhomogeneous distribution of Polyquaternium- 10 on treated fibers. Using the data given in these two publications results in a com- puted fractional polymer surface coverage of 23% for hair treated with Polyquaternium- 10 under conditions similar to those used in the present study. Obviously, the correla- tion is quite good. The inhomogeneous deposition behavior of this molecule may well reflect the inhomogeneous nature of the keratin substrate itself. DESIGNED EXPERIMENT FOR TREATMENT REPRODUCIBILITY The previous experiment clearly demonstrates the ability of ESCA to detect the adsorp- 299.8 Figure 2. Carbon Is high-resolution spectrum. A: control. B: Polyquaternium~10. C: Polyquaternium-24.