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j. Cosmet. sci., 52, 51-65 (January/February 2001) Quantitative methods for evaluating optical and frictional properties of cationic polymers WENJUN WU, JOY ALKEMA, GREG D. SHAY, and DAVID R. BASSET, Union Carbide Corporation, Cary, NC 27511. Accepted for pz/blication Jam/ary 15, 2001. Presented in part at the annual Scientific Seminar of the Society of Cosmetic Chemists, Chicago, May 6-7, 1999. Synopsis This paper presents three quantitative methods to examine gloss, opacity, and friction of cationic polymers. The adsorption of cationic polymers onto hair and skin can be regarded as a thin film coating. Therefore, optical and frictional properties of polymer films are of significant relevance to the applications of cationic polymers in hair care products. Such properties reflect the desirable hair condition attributes consumers seek in shampoo and conditioner products. Using these test methods, polyquaternium-10 and cationic guar samples of varying molecular weight and cationic substitution were compared. The effect of an artionic surfactant, sodium dodecyl sulfate (SDS), on polymer film properties was also investigated. Neat guar hydroxypropyl trimonium chloride imparts less friction than polyquaternium-10 but dulls the substrate employed in this study. The optical data show that polyquaternium-10 provides greater film clarity and gloss than cationic guars. In the presence of SDS, polyquaternium-10 also displays similar or lower friction than cationic guar. The comparative optical and frictional results are in good agreement with the visual assessment of the cationic polymer films. These results clearly demonstrate that polyquaternium-10 exhibits superior film properties in the forms of both neat polymer and polymer/surfactant complex. In addition, microscopic techniques such as scanning elec- tron microscopy (SEM) and atomic force microscopy (AFM) provide powerful explanations for the differences noted between the two popular classes of cationic polymers. The test methods described in this paper can be utilized to differentiate the upper performance potential of cationic polymers. These objective and standardized test methods derived from the coatings industry are not affected by the variability of hair or the formulation complexity of end products. They can be useful tools in the product development process in quickly screening the relative performance of different polymers. INTRODUCTION All hair care products are subject to consumers' sensory assessment. A common practice is to evaluate the hair conditions after product usage. For example, to differentiate cationic polymers, hair tresses are treated with straight polymer solutions or formulated shampoo products containing polymer. The hair condition attributes such as feel, ap- pearance, and ease of combing are then rated subjectively by a group of panelists. 51