CATIONIC POLYMER DEPOSITION ON HAIR 121 EXPERIMENTAL The preparation, purification, and characterization of fluorescein-modified cationic poly- saccharides have been reported elsewhere (14). The same techniques were used to label the cationic polysaccharides used in this study, namely several cationic hydroxyethyl celluloses (polyquaternium-10) and cationic polygalactomannans (guar hydroxypropyl- trimonium chloride). Table I shows the cationic polymers examined in this study, their solution viscosities, their cationic charge levels, and the levels of fluorescent dye incor- porated. The compositions of the shampoos prepared with the polymers are shown in Table II. Each shampoo was maintained at a pH of 7.0 that provides an optimum pH for fluorescent performance of the dye (13). The polymers were employed at 0.5 wt% in the shampoos for the purposes of this study. Five-gram swatches of virgin blond hair tresses, from one batch of hair purchased from DeMeo Brothers, were washed once with Cl1-15 Pareth-9, a non-ionic surfactant (Union Carbide, Danbury, CT), to remove residual oils and surfactants from the hair. Based on previous work, this treatment was considered to be the most practical for bringing all of the hair fibers into a nearly equivalent ionic state (4). One milliliter of the shampoo formulation was spread at three sites along each tress, and the tress was washed for one minute, rinsed in warm water (30øC) for one minute, and dried using a commercial 1500-watt hair dryer. Each data point represents the average value of measurements from five individual tresses washed one time and, in some cases, ten times with each shampoo. In multiple washing studies, the tresses were dried after each shampoo treatment. One gram of hair was carefully removed from the middle of each tress (unless otherwise specified). It was placed into 99 grams of a 3 wt% NaOH solution. The strongly alkaline solution was kept in the dark at room temperature for 24 hours, whereupon the hair disintegrates and dissolves. The resulting solution was neutralized to pH 7 using aque- ous HC1. All types of hair samples disintegrate in this alkaline medium however, virgin blond hair yields solutions that are nearly void of undissolved residues. Filtration of each solution through a fine fritted glass filter is performed nonetheless. A very small residue was recovered. This residue did not show any fluorescence upon irradiation with a UV light, implying that the amount of polymer trapped, if any at all, is extremely low. The solutions recovered after filtration were then examined by fluorescence spectroscopy, and Table I Cationic Polymers Dye level 4 Polymer INCI name Viscosity 3 (mol g • polymer) Charge level 5 A • Polyquaternium-10 Low 3.2 x 10 5 High B • Polyquaternium-10 Low 1.0 x 10 -4 Low C • Polyquaternium-10 High 5.4 x 10 -5 High D 2 Guar hydroxypropyl trimonium chloride Low 3.7 x 10 5 Low E 2 Guar hydroxypropyl trimonium chloride High 3.6 x 10 -5 Low Available from Amerchol Corporation, Edison, NJ. Available from Rhone-Poulenc, Cranbury, NJ. Low is 1000 cps at 25øC high is 1000 cps at 25øC (Brookfield viscosity). Determined by UV-Vis spectroscopy (14). Low is 1.2% cationic nitrogen high is 1.2% cationic nitrogen.

122 JOURNAL OF COSMETIC SCIENCE Table II Shampoo Ingredients Ingredient • Percent active Ammonium lauryl sulfate 2 14.0 Ammonium laureth-3 sulfate 2 3.9 Cocamidopropyl betaine 2 3 Cationic polymer 0.5 DMDM hydantoin 0.4 Deionized water 78.2 Nomenclature taken from International Cosmetics Ingredients Dictionary. Available from Henkel Corporation, Hoboken, NJ. the quantity of deposited polymer was determined by using standardization curves established previously with known quantities of each labeled polymer (17). Fluorescence images of individual hair fibers were taken using a Zeiss LSM10 laser scanning microscope equipped with Zeiss 20x and 10x objectives. An argon ion laser (488 nm) was used to image green emission. The images were acquired with a digital Sony 3 CCD camera. The hair samples were mounted on clean glass slides using a nonfluorescing aqueous/dry mounting medium (14). Rheological studies were con- ducted on a Bohlin CS rheometer (Bohlin Instruments, Cranbury, NJ) using a double- gap (DG) 40/50 cup and bob geometry. The rheological studies were run at 30øC, and the measurements were averaged over 40 seconds with a 0.1-second delay between measurements. Polymers employed in the rheological studies were dialyzed against distilled water (Spectra/Por © Membranes, 1000 MWCO, Spectrum Company, Houston, TX) and lyophilized prior to use. RESULTS AND DISCUSSION EFFECTS OF THE FLUORESCENT DYE ON POLYMER BEHAVIOR The fluorescent labeling of cationic hydroxyethyl cellulose was reported earlier (14) (Scheme I). The dye is a modified fluorescein. It is linked to the polysaccharide backbone through an ether linkage between a reactive triazine on the dye and an available hydroxyl group on the polysaccharide. The reaction occurs readily with various polysaccharides. For the present study we prepared labeled cationic hydroxyethyl cellulose and cationic polygalactomannan. Determination of the degree of substitution of the dye, and assess- ment of the purity of the resulting polymer, i.e., the absence of unreacted dye, were carried out as described earlier (14). In his seminal studies on the deposition of radiolabeled polyquaternium-10, Goddard reported that in the case of cationic polymers deposited directly from aqueous solution, polymers of lower molecular weight tend to deposit more quickly and more heavily (4,5). Goddard attributed the stronger deposition of the low-molecular-weight polymers to their higher mobility. He took it also as an indication of better penetration of these materials into the intercuticular spaces. Preliminary studies were done to reproduce with the fiuorescently labeled polymers the experiments carried out by Goddard and cowork-