SURFACTANT INTERACTIONS 271 Table II Deposition From Detergent Cleaning of SAC: Radiotracer Measurements •'2 Treatment 3 SAC per gram wool (mg) Detergent per gram wool (mg) Total deposit 4 1% SAC 6.68 (0.40) -- 6.68 (0.40) 5% ALS -- 1.94 (0.18) 1.94 (0.18) 1% SAC/5% ALS 4.58 (0.72) 4.09 (0.57) 6.73 (0.94) 5% SDES-2 -- 1.86 (0.22) [ 1.86 (0.22) 1% SAC/5% SDES-2 2.52 (0.47) 2.12 (0.33) 2.78 (0.57) • Numbers in parentheses are standard deviations. 2 Measured values connected by a vertical line were not significantly different. 3 0.3 ml of each treatment was applied. 4 Total deposits for conditioner/detergent washes are calculated by summing conditioner plus detergent deposits minus the detergent deposits on clean wool. seen that ALS deposition on conditioner-treated swatches was more than twice that on clean substrates. This confirms that lauryl sulfate anions interact with cationic SAC to form an insoluble complex. In the case of SDES-2, binding to clean or conditioner- treated swatches was virtually the same, proving, as was indicated by light scattering, that SDES-2 does not interact with SAC to form insoluble complexes on keratin sub- strates. The last column in Table II lists the total amount of deposit found on swatches after different treatments. For SAC-treated swatches washed with ALS, it can be seen that no net cleaning occurred: although some conditioner was removed by ALS, this was re- placed by detergent binding to the remaining SAC. In the case of the SDES-2 wash, on the other hand, the net effect was to remove 60% of the original deposit, thus again demonstrating the superiority of SDES-2 in cleaning conditioner. It should be noted in Table II that the amount of total deposit measured after washing conditioner-treated wool with detergent was adjusted by subtracting that amount of deposit measured after washing clean wool. This does not mean to imply that the subtracted detergent was not part of the conditioner/detergent complex, but was done simply to emphasize the excess of deposit resulting from washing conditioner-treated wool over that resulting from washing clean wool alone. Table III shows the results of radiotracer experiments in which CTAC was substituted for SAC. The results in this case were similar to those obtained with the latter condi- tioner. Almost three times as much ALS bound to CTAC-treated swatches as SDES-2, Table III Deposition From Detergent Cleaning of CTAC: Radiotracer Measurements • Treatment 2 CTAC per gram wool (mg) Detergent per gram wool (mg) 1.7% CTAC 7.13 (0.58) 1.7% CTAC/20% ALS 4.25 (0.13) 1.7% CTAC/5% ALS -- 1.7% CTAC/20% SDES-2 2.88 (0.33) 1.7% CTAC/5% SDES-2 -- 4.30 (0.63) 1.47 (0.15) Numbers in parentheses are standard deviations. 0.3 ml of each treatment was applied.

272 JOURNAL OF THE SOCIETY OF COSMETIC CHEMISTS indicating, as with SAC, that while CTAC does not interact with SDES-2 to form an insoluble complex, it does form such complexes with ALS on the wool surface. Because of this complex formation, only 40% of deposited CTAC was removed from wool swatches by ALSvs 60% by SDES-2. Total deposits could not be directly calculated because different concentrations of detergent were used in different experiments. It seems clear from the data, however, that, as with SAC, washing CTAC-treated swatches with ALS would result in little or no net cleaning. SURFACTANT SERIES EXPERIMENTS The preceding radiotracer experiments confirmed that light scattering can be used to evaluate cleaning of conditioners by surfactants. Using this methodology, the condi- tioner cleaning efficiency of a series of alkyl ether sulfates having carbon chain lengths of 6, 8, 10, and 12 and degrees of ethoxylation of 1, 3, and 5 was evaluated. Table IV presents the results for those detergents having a degree of ethoxylation of one. The results indicate that alkyl (lEO) ether sulfates with carbon chain lengths of 6, 8, and 10 are all effective in removing SAC from hair. The same was not found to be true for the C12 detergent, SLES-1EO, which, like TEALS, dulled the hair as a result of complex formation with SAC. The light-scattering results for the 3EO and 5EO detergents tested were found to be similar to those obtained with the corresponding lEO species. This indicates that, at least up to 5EO, formation of insoluble detergent:conditioner complexes is determined primarily by the length of the hydrophobic portion of the detergent rather than by the degree of ethoxylation. CLEANING OF SAC/TEALS COMPLEXES The preceding material showed that shorter-chain alkyl ether sulfates were superior to conventional, C12-based detergents in cleaning SAC and CTAC, because they do not form the insoluble conditioner:detergent complexes on hair that are formed by the latter surfactants. The above-mentioned experiments gave no indication, however, of the effectiveness of Table IV Shine of SAC/Detergent-Treated Hair • Treatment Shine 2 SODS 1.72 (0.23) SAC/C6- lEO 3 1.79 (0.22) SAC/C8- lEO 1.57 (0.09) SAC/C 10- lEO 1.58 (0.16) SAC/C 12- lEO 0.88 (0.07) SAC/TEALS 0.67 (0.07) • Shine values connected by a vertical line were not significantly different. 2 Numbers in parentheses are standard deviations. 3 This is a sodium hexyl ether sulfate substituted with one ethoxy group. The following surfactants in the column are all alkyl (lEO) ether sulfates with the designated carbon chain lengths.