CATIONIC POLYMER DEPOSITION ON HAIR 123 ers with radiolabeled polymers. Surprisingly good agreement between the two methods was obtained in the case of polyquaternium-10 deposition on hair (17). Goddard also studied the deposition of radiolabeled polyquaternium-10 from various simple surfactant platforms (5). The surfactants of most commercial relevance included triethanolamine lauryl sulfate (TEALS) and sodium laureth-3 sulfate (SLES). We repro- duced these deposition studies as closely as possible using fluorescently labeled polyquaternium-10 samples of charge and molecular weight characteristics similar to those of the polymers employed by Goddard in his studies. The results of our investi- gations are shown in Figure 1. The reproducibility of the deposition measurements for both labeling techniques from the strongly anionic surfactant, TEALS, is good. However, we note that from the milder surfactant system, SLES, deposition of the radiolabeled cationic polymer is greater than that seen for the fluorescently labeled polymer. The reasons for this discrepancy are unknown. One possible explanation is that the dye attached to the polymer somehow affects its deposition on hair when used in a milder surfactant system. Other factors might account for the discrepancy as well. For example, one cannot exclude the possi- bility of changes in the raw materials used in the original studies twenty-five years ago. Also, Goddard performed his deposition studies on virgin brown hair, while we have conducted ours on virgin blond. We do not believe this change accounts for the differ- ences noted. To assess whether or not the attached dye affects the behavior of the modified polyquaternium-10 in the presence of strongly anionic surfactants, we investigated the solution rheology of the labeled polymer both alone and in the presence of sodium dodecyl sulfate, SDS, at a concentration high enough to cause gelling of the polymer solution. This latter polymer/surfactant solution behavior was described previously by Goddard (18). The interaction of the cationic polymer and anionic surfactant leading to coacervate phases has been investigated microscopically (19). •mer La•l T•e and Wash •m bet ß Surfac•3 nt 15% ß Cationic Polymer 1.5% ß Laurarnide DEA 2.0% ß DMDM Hydantoin 0.4% ß Water q.s. to 100 Figure 1. Comparative study between radiolabeled polyquaternium-10 (grey bars) and fluorescently labeled polyquaternium-10 (black bars) from shampoos comprised of the ingredients shown in the small appended table (5). The data on the left was taken from a TEALS-containing shampoo and the data on the right from a shampoo with SLES. Data was generated for one and five wash cycles.

124 JOURNAL OF COSMETIC SCIENCE Examination of the solution viscosity of labeled and unlabeled Polymer A shows that the labeled polymer provides a slightly higher viscosity, but its shear-thinning rheology is comparable to that of the unlabeled polymer (Figure 2). The viscosity increase may be attributed to subtle changes of the hydrophobic or electrostatic interactions occurring between polymer chains upon attachment of a few dye residues. The effects intensify in the case of very-high-molecular-weight polymers. It is well known that slight changes in hydrophobicity cause significant changes in the solution behavior of high-molecular- weight polymers. When we examined the same two polymers in the presence of 0.25 wt% of SDS, we noted that both polymers build significant aqueous solution viscosity, as demonstrated earlier by Goddard (Figure 2). In this case too, labeled and unlabeled polymers produce gels of identical viscosity, although the labeled polymer solutions show some indication of enhanced sensitivity to high shear, as indicated by the disruption of solution viscosity at lower shear rate for this gel. However, we do not consider this change to be significant enough to interfere with the expected deposition mechanism for these polymers. QUANTITATIVE ANALYSIS OF POLYMER DEPOSITION ON HAIR It is generally acknowledged that cationic polymers deposited onto hair from shampoos bind to the surface as an associative complex of polymer and surfactant. Therefore, it is not possible to extrapolate deposition data obtained from simple polymer solutions to the behavior of the same cationic polymer in the presence of surfactants. For this reason, •' 1.00E+01 1.00E-01 Shear Stress (Pa) Figure 2. Viscosity versus shear rate response for labeled (¸, O) and unlabeled (0, ß) Polymer A as 1 wt% solutions (closed symbols) and as 1 wt% solutions gelled with 0.25 wt% SDS (open symbols).