J. Cosmet. Sci., 60, 239–250 (March/April 2009) 239 Evaluation of novel synthetic conditioning polymers for shampoos S. L. JORDAN, X. ZHANG, J. AMOS, D. FRANK, R. MENON, R. GALLEY, C. DAVIS, T. KALANTAR, and M. LADIKA, Dow Wolff Cellulosics, A Subsidiary of the Dow Chemical Company, 171 River Road, Piscataway, NJ 08854 (S.L.J, X.Z., J.A., D.F., R.M., R.G., C.D., M.L.), and the Dow Chemical Company, Building 1712, Midland, MI 48674.(T. K.). Synopsis Cationic polymers have traditionally been used in shampoo formulations to impart conditioning properties to hair. In this study, commercial synthetic cationic polymers were investigated using coacervate formation, objective wet comb analysis, silicone deposition and panel studies to determine structure function properties with the goal of developing novel conditioning polymers. New polymers were synthesized and, based on criteria determined in the fi rst part of the study, found to have marginal improvement over existing synthetic cationic conditioning polymers. A novel experimental polymer developed for a different industry was also investigated for conditioning properties. This polymer showed signifi cant enhancement of silicone deposition over current commercial polymers, including cationic guar, even at signifi cantly reduced silicone and polymer concentrations. The experimental polymer exhibited parity or improvement over benchmark polymers in panel studies, and similar performance to other synthetic polymers in objective wet comb studies. BACKGROUND For over thirty years cationic conditioning polymers have been used in anionic shampoo formulations to impart improved look, feel comb properties (1,2). These polymers are also used as deposition aids for benefi t agents such as silicone. Two naturally derived cat- ionic polymers, cationic hydroxyethyl cellulose (polyquaternium 10 or PQ10) and guar hydroxypropyltrimonium chloride (cationic guar) are used extensively in the market to- day. Hydrophobically modifi ed PQ10 (PQ67) was recently introduced as well. Less widely used are various synthetic conditioning polymers including acrylamide and dimethyl diallyl ammonium chloride (polyquaternium 7 or, PQ7) and polyvinyl pyrrolidone and dimethyl aminoethylmethacrylate, (polyquaternium 11 or PQ11) (3). In general, cat- ionic conditioning polymers coexist in shampoos with anionic surfactants in a single phase. As the shampoo is diluted during use and the surfactant approaches the critical micelle concentration (CMC), the cationic polymer forms a complex with the surfactant monomers that phase separates from the bulk solution. This phase separation, or coacer- vation, is known as the Lochhead effect (4–7). The gel-like coacervate contains a high concentration of the cationic polymer which is then deposited onto the negatively charged

JOURNAL OF COSMETIC SCIENCE 240 hair, forming a clear fi lm. Insoluble actives (e.g. silicones) are effectively trapped in the coacervate and deposited along with the polymer. While PQ10 and cationic guar are the most widely used conditioning polymers, the large variety of monomers available to make synthetic polymers has led to an explosion in the development of synthetic cationic polymers. Previous work with PQ10 and the hydro- phobe modifi ed PQ24 and PQ67 showed signifi cant effects of changing parameters such as molecular weight, charge density and hydrophobic substitution on polymer perfor- mance (Figure 1) (4,8,9). Using these structure function relationships, polymers can be fi ne tuned to obtain customized effi cacy for deposition, wet comb and dry conditioning properties. In the case of the naturally derived polymers, the structural changes are limited by the polymer backbone provided by nature. In contrast, the backbone for synthetic polymers can be changed and is limited only by the availability of monomers, giving the synthetic chemist additional “levers” to alter polymer performance. One of the key differences between natural and synthetic polymers is backbone fl exibility in solution. Natural polymers tend to have a more rigid backbone while synthetic poly- mers are more fl exible. While polymer performance is related to the ability to form coacervate and subsequently deposit on hair, the conformation of the polymer on the substrate and the surface properties it imparts to the hair are of equal, if not greater, importance to overall conditioning properties. It is unclear how backbone fl exibility affects polymer conformation and properties on the substrate. According to the Personal Care Product Council website (http://www.personalcare council . org/), there were 88 polyquaternium polymers with INCI names in 2008 compared with 42 Figure 1. Cationic hydroxyethyl cellulose (PQ10, PQ24, and PQ67) can be modifi ed via molecular weight, charge density and hydrophobic substitution. Backbone composition can be designed for synthetic polymers.