2006 TRI/PRINCETON CONFERENCE 453 microscope (Figure 2). The major stress then leading to hair fracture is not just one of stretching such as is measured by tensile strength, but rather flexure or bending (5 ). Combing, then, is the major route that fibers tend to split since these shear forces are necessary to fracture the hair which eventually will lead to a split end. However there are many factors which weaken the hair that predispose it to split during the combing process (6). There are many references on the effects of UV on the degradation of the different structures of hair. One reference is a review of our current understanding of the subject and options for photoprotection (7). Other damaging factors that are noteworthy to mention are chemical processing such as bleaching (8), thermal (9), thermal- mechanical damage (brush and blow dry) (10), and damage from surfactants which can be translated to multiple shampooing (11). Even if hair has not been purposely damaged, the hair at the tip end being older than at the root has suffered more wear and tear and would tend to split during combing. It is necessary therefore when designing a test method that will be used to test the efficacy of a composition to mend split ends to incorporate into the procedure the same combing forces that are present during everyday grooming. Without this the fibers will not be subjected to the same degree of shear forces during combing and the durability of the mended fiber cannot be assessed. This aspect of testing the durability of the split end mend has been incorporated into the test method used in this study. Subjecting hair to realistic combing forces allows the assessment of not only the initial mending after treatment, but more importantly the durability of the mend such as a post combing treatment. With this method various Figure 2. Dynamic bending of hair as comb is passed through cress.

454 JOURNAL OF COSMETIC SCIENCE polymer systems were tested for their ability to mend split ends. The experimentation evolved from testing individual polymers to polymer blends where it was discovered that a polyelectrolyte complex, formed between the ionic interactions of two oppositely charged polymers, provided positive effects in the mending process. The novel compo- sition was found to have durability to a post combing treatment and was still able to be washed off the hair after a post shampoo treatment. Based on these features it was characterized as a semi-permanent hair repair effect. Besides a description of the poly- electrolyte complex used in this study, as well as test results, a proposed theory of the mechanism of mending is described. This mechanism serves as a model for designing other complexes that will have the same hair mending effect. MATERIALS AND METHODS MATERIALS Natural brown hair tresses are supplied by International Hair Importers and are made with their patented swatching process to be 3.5 grams of loose hair, 6.5 inches in length from the bottom of the sewn end to the tip of the hair, and 1 3/4 inches across. Brand of combs used in the experiments are Sally's Beauty Supply. Fine teeth section of the comb contains eight teeth per centimeter. The free acid form of the copolymer of methyl vinyl ether and maleic anhydride (INCI: PVM/MA Copolymer) is supplied by International Specialty Products under the trade name Gantrez® S-97 BF Polymer. The copolymer of vinyl pyrrolidone and methacryl- amidopropyltrimethyl ammonium chloride (VP/MAPTAC Copolymer INCI: Polyquaternium-28) is supplied by International Specialty Products under the trade name Conditioneze® NT-20. This is a 20% (w/w) solution in water. These ingredients are used as supplied and not purified or modified in any way. Figure 3 illustrates the structures of these compounds. A commercial product with a split end mending claim was used as a benchmark. Its' ingredient label is: Aqua/Water, Cyclopentasiloxane, Propylene Glycol, Hydroxypropyl Guar, Phenoxyethanol, Peg 40 Hydrogenated Castor Oil, PEG/PPG-17/18 Dimethi- cone, Behentrimonium Chloride, Aminomethyl Propanol, Trideceth-12, Polyquate- rium-4, Dimethiconol, Limonene, Linolool, Benzyl Salicylate, Amodimethicone, Alpha- Isomethyl Ionene, Perea Gratissima/Avocado Oil, Carbomer, Potato Starch Modified, Methyl Paraben, Butylphenyl Methylpropional, Citronella!, Cetrimonium Chloride, Laureth-23, Laureth-4, Prunus Armeniaca/Apricot Kernel Oil, Coumarin, Hexyl Cin- namol, Parfum/Fragrance, F.I.L. Cl638713 EQUIPMENT • Nikon SMZ 1500 Stereomicroscope • Linksys 2.2 program for digital imagery (Linksys for Windows, Linkam Scientific Instruments Inc., 8 Epsom Downs Metro Center, Waterfield, Tadsworth, Surrey, KT205HT, U.K.) • Thermal/Mechanical Styling Apparatus custom built at ISP to produce tresses with split ends. • Amray model 1820/D digital Scanning Electron Microscope (SEM) with a LaB6