]. Cosmet. Sci., 58, 451-476 CTuly/August 2007) Semi-permanent split end mending with a polyelectrolyte complex R. RIGOLETTO, Y. ZHOU, and L. FOLTIS, International Specialty Products, 1361 Alps Road, Wayne, N.J. 07470. Synopsis Split ends form through mechanical stresses during grooming procedures and are more likely to appear in hair damaged as a result of excessive combing forces. Although there are no conventional systems that will permanently mend split ends, a semi-permanent mending composition has been achieved through a poly- electrolyte complex. The complex is formed as a result of the ionic association of a cationic polymer, Polyquaternium-28, and an anionic polymer, PVM/MA Copolymer. Hair tresses containing tagged split ends are used in measuring mending efficacy. The tagging allows the fate of the split ends to be determined after different types of treatment regimens which test the durability of the mend. Monitoring of the repair and mending durability is carried out with the aid of a stereomicroscope. Results obtained with this method indicate that the complex both by itself and when formulated into a simple lotion provided a high level of split end mending not only after initial treatment but more importantly after combing showing the durability of the mend. Cumulative effects and durability to washing indicate that the polymer complex does not build up on the hair and rinses off with shampoo making possible its usage as a post shampoo treatment. The formulated lotion has higher durability performance as compared to a commercial product with a split end mending claim. The proposed mechanism of action entails a crosslinking microgel structure that infiltrates the damaged hair sites binding them together. This model is supported by the analysis of phase behavior, viscometry, Scanning Electron Microscopy, and absorption of ionic dyes. INTRODUCTION The manifestation of damaged hair as seen macroscopically as we view whole hair attributes is based on the state of each of the individual fibers taken collectively. Different types of damage are observed on a microscopic scale using scanning electron microscopy as a diagnostic tool (1). These consist of transverse fractures through the hair's cuticle, transverse fractures of the whole fiber, delamination within the cuticle, longitudinal splitting of the hair shaft (split ends), and multiple longitudinal splitting of the hair shaft (trichorrhexis nodosa) (2). Each of these structural maladies when multiplied by the number of fibers is portrayed in whole hair attributes such as dullness, lack of manageability or stylability, rough texture, and poor combability. The hair as a whole based on the state of the individual fibers looks unhealthy. There are multiple causes for this damage and encompass physical, chemical, and en- vironmental factors. Versatility of hair styles is a major cause of the predominance of hair damage. Consumers desire products that allow them to express their individuality and personal style to a greater extent. Keeping up with the latest hair style fashion includes 451

452 JOURNAL OF COSMETIC SCIENCE oxidative hair coloring and permanent waving. Also styling agents in combination with styling implements such as curling and flat irons allows one to have a different hair style even from one day to the next. The result of this increased amount of styling has its effect on the quality and condition of the hair. This is compounded with longer hair styles since the ends of the hair are older and have experienced more weathering as well as the aggressive styling treatments. Eventually the hair becomes dull, unmanageable, coarse to the touch, and hard to comb. When viewing these damaged fibers on a microscopic scale one realizes the cause of what is observed on the macroscopic scale. With the predomi- nance of aggressive styling behaviors it is clear that there is a market need for compo- sitions and products that are able to not just prevent hair damage but, what is more challenging, affect its repair. One manifestation of damage that affects whole hair attributes are fibers that have split longitudinally at their tip ends. The technical term for split ends is trichoptilosis. The theory of split end formation as proposed by Swift is fully elaborated in an article entitled Mechanism of split--end formation in human head hair (3) and is depicted in Figure 1. A clue that led to the theory on the mechanism of split end formation was from an SEM of a split end fiber. It was observed that the split occurred in such a manner that it formed parallel to the major axis of the hair diameter (4). Swift theorized that when hair is combed the elliptically shaped hair fibers preferentially orientates so that the major axis is parallel to the surface of the comb tooth. As the comb traverses the hair, shear stresses are produced parallel and longitudinal to the major axis of the fiber. The degree of shear stress is distributed parabolically along the minor axis of the hair so that the shear plane suffering the most shear stress would be that running parallel to the major axis of the hair. When the shear force becomes great enough tiny fractures occur along this axis and eventually will propagate to the end of the fiber. As the comb is pulled through the hair the bending is propagated from root to tip it is not a static bend. As the comb reaches the tip end of the tress the collection of fibers tend to snarl increasing the shear stresses to a greater extent at the tip than anywhere else along the fiber length. Fibers are dynamically bent over 180 degrees as observed under a stereo- Shear stress y axis Figure 1. Mechanism of split end formation showing the distribution of shear stresses in fiber during combing. Depiction of theory proposed by Swift (3).