SYNTHETIC HAIR CONDITIONING POLYMERS 29 panelists indicated a slight preference for the reference tresses for dry feel and dry comb- ing, but in the wet feel and wet combing categories, they indicated a slight preference for tresses treated with P2-containing formulation. In the comparison of hair tresses treated with PQ-67 and P3, the panelists indicated a very slight preference for tresses treated with the P3-containing formulation in wet feel and wet combing properties, whereas for dry feel and dry combing, they did not observe differences between tresses treated with the PQ-67- and P3-containing formulations. Finally, for hair tresses treated with formu- lations containing P3 or P1, the panelists indicated a strong preference in all four categories for tresses treated with P3 formulation. In summary, among shampoo formulations pre- pared with the three new synthetic polymers, panelists had either a very slight or equivalent preference for the formulation prepared with P3 compared with PQ-67. This is in agree- ment with wet combing results obtained using the automated parallel tensile tester, in which P3 was identifi ed as the most effective synthetic conditioning polymer in this study. SILICONE DEPOSITION Conditioning polymers are also used to deliver silicone conditioners to the hair during the wash/rinse process therefore, the effect of polymer additives on silicone deposition was stud- ied. Figure 4 summarizes the results of this study. Cationic guar and UCARE™ JR30M were used for comparison of silicone deposition as they are often used in silicone-containing sham- poos. The formulation with cationic guar enabled deposition of 597 ppm silicone, whereas the formulation with P3 enabled deposition of 5,000 ppm silicone ( 8-fold increase). Beyond the general structure–property relationships known for conditioning polymers (36), the spe- cifi c polymer structural features responsible for the observed differences in silicone deposition onto the hair strands, and wet and dry combing work and feel properties are unknown at this time, but could involve nuanced differences in polymer molecular weight, charge density and distribution, and interaction with the shampoo surfactants, as well as the manner in which the polymer interacts with the hair strand during washing and rinsing (37). The increased silicone deposition exhibited by this polymer in this preliminary study leads to the question of whether it will behave like cationic guar, which suffers from enabling excessive silicone build-up over time on hair (30) further characterization beyond the scope of this initial work will be needed. However, the high silicone deposition levels enabled by P3-based Table VI Results from the Panel Study: Fraction of Panelists (%) Who Preferred the Shampoo Containing the Listed Polymer Polymer Wet feel Wet comb Dry feel Dry comb PQ-67 80 80 80 80 P1 20 20 20 20 PQ-67 30 30 60 60 P2 70 70 40 40 PQ-67 40 40 50 50 P3 60 60 50 50 P1 20 20 20 20 P3 80 80 80 80

JOURNAL OF COSMETIC SCIENCE 30 shampoos may give the formulator some fl exibility to balance combing/feel with deposi- tion, possibly enabling use of less polymer or less silicone (an expensive component) in the formulation. C ONCLUSIONS I t has been demonstrated in this preliminary work that a high throughput combinato- rial synthesis and screening approach can be used to identify the compositions of po- tential high-performance synthetic cationic conditioning polymers. A high throughput method for polymer synthesis was used to prepare cationic polymer candidates which were characterized by monomer conversion, % polymer solids, molecular weight and PDI, haze, and viscosity. Shampoo formulations were prepared in a single shampoo base with those polymers that demonstrated the required clarity and high monomer conver- sion in high throughput screens. Hair tresses were treated with these shampoo formulations for subsequent testing of wet combing and wet feel in initial performance screens. Numerous polymers in the tested shampoo formulations enabled substantial reduction in wet combing work, apparently showing greater wet comb performance than a shampoo formulation made with a cellulosic polymer, PQ-67. A shampoo formulation contain- ing polymer P3 was only slightly hazy and exhibited lower wet combing work relative to a PQ-67-based shampoo. A panel study indicated similar performance of PQ-67- and P3-containing shampoo formulations. A shampoo formulation with P3 enabled greater silicone deposition (by 8-fold) than a formulation made with cationic guar. P3 is a wholly vinyl monomer-based cationic conditioning polymer with hair conditioning effi ciency equal to or greater than that of PQ-67 in the shampoo formulation studied. Further studies will be needed to elucidate the specifi c polymer microstructural basis of the observed conditioning effi cacy in this one formulation, as well as the range of formulations and treatments in which it is effective. A CKNOWLEDGMENTS W e are grateful to the Dow Chemical Company, to FreeSlate (now Unchained Labs), and to Damian Hajduk, Robert Mussell, Greg Cardoen, and Curtis Schwartz for their support Figure 4. Silicone deposition onto hair from shampoo formulations containing different conditioning poly- mers. Dark bars are error bars.