2005 ANNUAL SCIENTIFIC MEETING Electrolyte and Order of Addition Effects. The effect of a monovalent electrolyte (NaCl) on coacervate amount and structure was investigated for three of the above cationic polymer/anionic surfactant systems JR400, JR30M and LRJ0M. These polymers were chosen because they exhibited coacervate formation and structuring in the absence of salt and they also provide direct analysis of the impacts of both molecular weight (JR400 vs. JRJ0M) and charge density (LRJ0M vs. JRJ0M). Using high-throughput techniques, six orders of addition were investigated for systems that contain cationic polymer, anionic surfactant, sodium chloride and water. Aqueous solutions of the component ingredients (Polymer, surfactant and salt) were added sequentially to each vial then subsequently mixed by vortexing. Representative results of these Salt Addition Order studies are shown in Figure 3. �2 potynw,,awtac:tard..watert,. �J �. WIAf/11 .... polymef Figure 3. Salt Addition Order results for JR400. Graphs on left show coacervate amount (phase separation) and graphs on right show coacervate structure (birefringence). JRJ0M and LRJOM results show the same trends as JR400, but absolute numbers are different due to molecular weight and charge density differences. The regions of birefringence do not always coincide with the regions of phase separation. Therefore, there are phase separated coacervates that do not have micellar liquid crystalline structure and mesomorphically structured regions that appear to exist in a single-phase. The differences observed in these diagrams can be explained on the basis that intimate contact of polyelectrolyte with salt causes the polyion to collapse and the salt shields the ion-ion interaction between the surfactant anions and the polyion. Therefore, coacervate formation is prevented in the ion-exchange region of low surfactant concentration and high polymer concentration. Alternatively, intimate contact of surfactant and salt will increase the intrinsic size of the surfactant micelles and reduce the micellar surface charge density. Subsequent interaction of the expanded polyion with these large surfactant micelles results in the formation of coacervate at relativity high concentrations of surfactant and low concentrations of polyelectrolyte. CONCLUSIONS High-throughput screening formulation methods developed in our research group have allowed us to develop predictive models for coacervate amount and coacervate structure formed in three component systems. Using these methods we have also observed significant changes in the compositional region of coacervate composition depending upon the order of addition of the component ingredients. These changes can be rationalized by consideration of the polyion conformation and the mice liar size and structure when these components are initially mixed. ACKNOWLEDGEMENTS The authors wish to thank Amerchol and Stepan Co. for supplies and The Society of Cosmetic Chemists for funding. 83

84 JOURNAL OF COSMETIC SCIENCE THE PHYSICAL CHEMISTRY OF HAIR FIBER ARRAY-WATER INTERACTIONS The problem Miklos M. Breuer, Ph.D. 1501 Beacon Street, Brookline, MA 02446 mbreuer@msn.com Fiber to fiber interactions are known to affect the behavior and esthetic attributes ofhair-do-s (coiffures). Whereas the effects of atmospheric on properties of single hair fibers have been extensively studied, the influence of humidity on inter-fiber interactions is still not well understood. Although wet-combing has being widely used as an empirical technique for evaluating hair damage and hair conditioning product efficacy, the physical chemical factors linking the experimentally measured combing forces with characteristic quantities of water-hair surface interactions, are still unknown. Similarly, the reasons for the tendency of long, straight hair to clump into unseemly, streaky bundles at high humidity are still unclear. In a recent publication in Nature, Jose Bico et al. 1 outlined a quantitative model linking the physical properties of fiber assemblies to their macroscopic behavior. I developed this model further and to applied it to specific practical problems that cosmetic scientists, who work on hair product development, encounter in their day to day work. Thus, in this paper I propose to describe the quantitative relationships that exist between the characteristic physico-chemical properties of single hair fibers ( e.g. fiber-surface energy, fiber- coarseness, fiber-rheology, hair fiber density, etc), and the behavior of hair fiber assemblies. In particular, I propose to discuss the effects of single fiber properties on a.) the wet-combing forces b.) the extent of clumping (i.e. splitting into bundles, average bundle size, etc.) that occurs especially when coiffures of long straight hair are exposed to atmospheric humidity, and c.) the amount of inter-fibrillar water that hair arrays absorb and retain at various humidity conditions. The Model Initially model looks at the behavior of two adjacent fibers with square cross-sections that are brought into contact with water (Figure l , 2). The fibers are made ofan elastic material having a bending stiffness ofK, and a surface energy ofy,. When brought into contact with water, owing to capillary forces, the two fibers will absorb inter-fibrillar water and stick together. (Fig 2) The length of the inter-fiber water column will be determined by an equilibrium between the capillary forces that pull the fibers together and the counteracting elastic bending forces that try to restore the fibers to their original configurations. (the magnitude of gravitational forces is negligible in this instance). The length of the inter-fiber water column will also depend on the thermodynamic potential (humidity) of the water in the surrounding atmosphere. The equations describing this model can be written as: (1) Where K, d, p, My, 9, R,T, hare the bending stiffness, the inter-fiber distance, the density of water, the surface energy of water, the contact angle of water on the fiber surface, the molecular weight of water, the gas constant, the absolute temperature and the atmospheric humidity, respectively. Furthermore, Ld, the length of dry section of the fiber is defined by