JOURNAL OF COSMETIC SCIENCE 16 (28) Z. Abdel Naser and A.-R. Rowa, Knowle d ge and attitudes of Palestinian University students toward the use of sunscreens, 5(3), 120–122 (2012). (29) US Food and Drug Administration, 2016. FDA authority over cosmetics: how cosmetics are not FDA- approved, but are FDA-regulated. fda. gov/Cosmetics/GuidanceRegulation/LawsRegulations/ucm074162. htm and ‘Prohibited and Restricted Ingredients’, fda. gov/Cosmetics/GuidanceRegulation/Laws Regulations/ ucm127406. htm notes to, pp.88–102. (30) FDA, Inactive Ingredients Database Do w nload. Draft Guidance (US Food and Drug Administration, Rockville, MD, 2016). (31) Qu D, Seehra GP. Improving the accuracy of skin elasticity measurement by using Q-parameters in Cutometer. J Cosmet Sci. 2016 Jan-Feb 67(1):37–44.

J. Cosmet. Sci., 72, 17–32 (January/February 2021) 17 Application of Combinatorial Methods for the Identifi cation of Synthetic Hair-Conditioning Polymers THOMAS H. KALANTAR, MLADEN LADIKA, TATIANA V. DROVETSKAYA, ADAM SAFIR, STEVEN ZONG, XINNAN ZHANG, and SUSAN L. JORDAN , Herbert D. Doan R&D Center, The Dow Chemical Company, Midland, MI (T.H.K., M.L.), FreeSlate, Inc., Sunnyvale, CA (A.S., S.Z., X.Z.), The Dow Chemical Company, Bound Brook, NJ (S.L.J., T.V.D.) Accepted for publication August 31, 2020. Synopsis Cationic conditioning polymers have a role as deposition aids for depositing benefi t agents such as silicone polymers and are used in shampoo formulations to provide improved combing properties, feel, and look. The objective of this work was to develop synthetic high-performance polymeric conditioning agents that exhibit conditioning performance as good as, or better than, the current commercially available polymers. We describe the application of high throughput methods to identify high-performance synthetic hair-conditioning polymers through using high throughput combinatorial methods for polymer synthesis and screening to prepare several hundred cationic polymer candidates. Shampoo formulations were then formulated with these polymers hair tresses were treated with these formulations and tested via a parallel automated wet combing method. Three high-performing polymer candidates were selected for further evaluation, prepared on a larger scale and evaluated via a panel study. A (3-acrylamidopropyl)trimethylammonium chloride-vinyl monomer-based cationic copolymer is shown to exhibit hair conditioning effi ciency equal to or greater than that of a high-performance cellulose ether-based polymer, SOFTCAT™ SL-5 (Polyquaternium-67) in a shampoo formulation. I NTRODUCTION AND BACKGROUND Cationic conditioning polymers are used in shampoo and body wash formulations to provide improved combing properties, feel, and appearance (1–3). The impact of these polymers on hair and skin conditioning is dependent on many factors relative to the polymer itself (polymer architecture, molecular weight, charge density and distribu- tion, presence or absence of hydrophilic and hydrophobic moieties, etc.) as well as on the properties of the shampoo, conditioner, body wash, or two-in-one formulation in which Address all correspondence to Thomas H. Kalantar at tkalantar@dow.com and Susan L. Jordan at susan. jordan@dupont.com