CATIONIC POLYMER DEPOSITION ON HAIR 125 we developed the model shampoo system shown in Table II. This shampoo formulation is comprised principally of a strong anionic surfactant, ammonium lauryl sulfate (ALS), a surfactant commonly used in the personal care industry. It closely mimics the TEALS surfacrant used in the model studies described previously. It is critical to keep in mind that the data presented below, strictly speaking, apply only to the deposition onto virgin blond hair of the labeled polymers present in a shampoo prepared according to the formulation presented in Table II. Any changes to the shampoo formulation, or changes in hair type, are likely to change the polymer deposition and adsorption behavior. Influence of cationic polymer viscosity (molecular weight) on ckposition. We investigated the effect of polymer viscosity on the cationic polysaccharide's deposition (Figure 3). For this study, we selected Polymers A and C, two polyquaternium-10 samples of similar cat- ionic substitution but different viscosities, and Polymers D and E, two commercial cationic guar derivatives of similar charge levels but different viscosities. As seen in Figure 3, the influence of polymer molecular weight on polymer deposition is signifi- cant. For both types of cationic polysaccharides, the deposition of the high-viscosity (high-molecular-weight) polymers is significantly higher than the deposition of the corresponding low-viscosity (low-molecular-weight) polymers. For polyquaternium- 10, this trend is the opposite of the sorption behavior reported by Goddard for the polymers when the same polymers were delivered to hair from aqueous solutions, in the absence of surfactant (5)! This result confirms the significant impact of the surfactant on the deposition and adsorption of cationic polymers onto keratin surfaces. This sorption behavior may be related, in part, to the rheology of the polymer/surfactant complexes formed during deposition. Higher-molecular-weight polymers form more viscous asso- ciative complexes, hindering the removal of the deposits from the hair during rinsing. Efjbct of cationic charge level. To assess the effect of charge on polymer deposition from shampoos, we selected Polymers A and B, which vary in their levels of cationic charge. Polymer A has twice the level of cationic charge, compared to Polymer B, but the two polymers have similar molecular weights. We did not detect a significant difference in the amount of polymer deposited from these two shampoos, at least within the range of 35O 0 (0.27) (1.36) (0.44) Polymer A (Ix) Polymer C (1){) Polymer D(1X) Cationic Polymer Type (0.33) .. Polymer E (lx) Figure 3. Deposition data (including relative standard deviations) for low-viscosity polymers A and D and high-viscosity polymers C and E after a single wash cycle.

126 JOURNAL OF COSMETIC SCIENCE experimental error of the technique (Figure 4). Therefore, while it is important that the polymers carry positive charges for deposition to occur, the amount of charge does not affect deposition to the same extent as molecular weight. It should be pointed out that Goddard demonstrated also by radiolabeling studies that cationic charge was essential for polymer adsorption onto hair and skin (5). Efj•ct of multiple washings on polymer deposition. The effect of multiple washing cycles on polymer deposition is critical information that the formulator needs to know in order to understand the mechanism of polymer build-up. The perception of build-up of a prod- uct, such as a conditioning shampoo, as a result of its repetitive use is detrimental to its acceptability by consumers. The study of the effect of multiple washings on cationic polymer deposition was carried out with a low-viscosity polyquaternium-10 sample, Polymer B. In the case of the strong anionic surfactant platform used here, the sorption of polyquaternium-10 is relatively constant through the course of ten washing cycles (Figure 5). No significant build-up of polyquaternium-10 on the hair tress was detected, within the range of error for the measuring technique. Indeed, polymer build-up de- pends critically on the hair type and on the nature of the shampoo composition, in particular the choice of surfactants, the polymer concentration, and physical properties. Polymer deposition at difj•rent tress locations. It is well known that as hair ages, damage from various physical, environmental, and chemical factors gradually erodes the protective cuticle layers, eventually exposing the native proteins of the hair cortex. Virgin hair has not been exposed to the ravages of chemical dyeing and perming and is, therefore, relatively damage-free. We examined the amount of polymer deposited in three different locations on the virgin blond hair tresses using a shampoo made with high-viscosity polyquaternium-10, Polymer C. Deposition at the distal end and middle of the tress was similar, but there appeared to be slight reduction in deposition at the proximal end of the tress (Figure 6). This was not unexpected, as the proximal end of the tress is newer hair. We should point out also that during preparation, the tresses were rinsed in such a way that the rinse water flowed from the proximal to the distal end of the hair tress. Thus, it is not unreasonable to consider the possibility that rinsing moves the more weakly bonded polymers down the tress. As this rinsing pattern is typical of standard 3O 20 •E,15 •- 0 o & 5 (0.17) (1.36) Figure 4. Effect of cationic polymer charge level on polymer deposition. Single wash data. Polymer A (lx) Polymer B (lx) Polyq uate rn iu m -10 variant