18-MEA DEPOSITION ON HAIR 37 ether sulfate (2.5 E.O.) with 2 wt% N,N-bis (2-hydroxyethyl)-dodecanamide solution adjusted to pH 7 with phosphoric acid], are shown in Figure 4. The chemical structures of these surfactants are shown in Figure 5, and the conditioner formulations are listed in Table II. When alkaline-color-treated weathered hair was treated with the 18-MEA/ SPDA complex (conditioner 1), the contact angle became nearly 90°, approaching that of normal hair. To further investigate the differences in the dynamic contact angles, analysis of variance (ANOVA) was conducted. It demonstrated that there were signifi cant differ- ences in the contact angle between the hair treated with the 18-MEA/SPDA complex (conditioner 1) and alkaline-color-treated weathered hair, and that there were not sig- nifi cant differences in the contact angle between the hair treated with 18-MEA/SPDA complex (conditioner 1) and normal hair. This means that the surface of alkaline-color- treated weathered hair treated with the 18-MEA/SPDA complex (conditioner 1) could maintain its hydrophobicity even 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 pH7 with phosphoric acid], while the hair treated with other complexes could not. Figures 6 shows the dynamic friction coeffi cient of alkaline-color-treated weathered hair treated with 18-MEA/SPDA, 18-MEA/DAPS, and 18-MEA/STAC complexes. The dy- namic friction coeffi cient of alkaline-color-treated weathered hair treated with the 18- MEA/SPDA was the nearest to that of normal hair, and it was much lower than that of hair treated with the other complexes. To further investigate the differences in the dy- namic friction coeffi cient, analysis of variance (ANOVA) was conducted. The results of ANOVA showed that there was a signifi cant difference in the dynamic friction coeffi cient between the hair treated with the 18-MEA/SPDA complex (conditioner 1) and alkaline- color-treated weathered hair, and that there were no signifi cant differences in the dynamic friction coeffi cient between the hair treated with the 18-MEA/SPDA complex (condi- tioner 1) and normal hair. That means that the surface of alkaline-color-treated weathered Figure 4. Contact angle of alkaline-color-treated weathered hair treated with 18-MEA complexes after shampooing. The bars represent means for n=7 the whiskers represent the standard deviations. The p-value was obtained from ANOVA analysis. (a) Normal hair. (b) Alkaline-color-treated weather hair. (c) 18-MEA/ SPDA (conditioner 1). (d) 18-MEA/DAPS (conditioner 2). (e) 18-MEA/STAC (conditioner 3). (f) Control (conditioner 6). Figure 5. Chemical structures of surfactants. (a) Stearoxypropyldimethylamine (SPDA). (b) Dimethylam- inopropylstearamide (DAPS). (c) Stearyltrimethylammonium chloride (STAC).

JOURNAL OF COSMETIC SCIENCE 38 hair treated with the 18-MEA/SPDA complex (conditioner 1) could maintain its low fric- tion even 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 pH7 with phosphoric acid], while the hair treated with other complexes could not. Figure 7 shows the amount of 18-MEA sorption in alkaline-color-treated weathered hair treated with 18-MEA/SPDA, 18-MEA/DAPS, and 18-MEA/STAC complexes measured by LC-MS. Figure 8 shows the relative ion yield of 18-MEA versus the total ion yield of alkaline-color-treated weathered hair treated with 18-MEA/SPDA, 18-MEA/DAPS, and 18-MEA/STAC complexes measured by TOF-SIMS. As we expect from the contact angle and surface friction results, the amount of 18-MEA absorbed on the surface of alkaline- color-treated weathered hair treated with the 18-MEA/SPDA complex was much higher than that of hair treated with the other complexes. Figure 6. Dynamic friction coeffi cient of alkaline-color-treated weathered hair treated with 18-MEA com- plexes after shampooing. The bars represent means for n=5 the whiskers represent the standard deviations. The p-value was obtained from ANOVA analysis. (a) Normal hair. (b) Alkaline-color-treated weathered hair. (c) 18-MEA/SPDA (conditioner 1). (d) 18-MEA/DAPS (conditioner 2). (e) 18-MEA/STAC (conditioner 3). (f) Control (conditioner 6). Figure 7. Amount of 18-MEA sorption of alkaline-color-treated weathered hair treated with 18-MEA com- plexes after shampooing, measured by LC-MS. The bars represent means for n=3 the whiskers represent the standard deviations. (a) 18-MEA/SPDA (conditioner 1). (b) 18-MEA/DAPS (conditioner 2). (c) 18-MEA/ STAC (conditioner 3).