EFFECT OF ANTEISO-BRANCH MOIETY OF 18-MEA 511 (90 times) was done between every interval of alkaline coloring. This resulted in a process of alkaline coloring combined with daily weathering, that simulated a one-year period, assuming the hair is alkaline colored every three months. The model weathering treat- ment consists of a series of daily hair care procedures: shampooing, conditioning, drying with a hot dryer, and brushing. Hair tresses (5 g) were treated with an alkaline-colored lotion (3.5 wt% hydrogen peroxide, 0.76 wt% ammonia, 5.6 wt% ammonium bicarbon- ate, 2.0 wt% cethyl trimethylammonium chloride, 0.05 wt% EDTA/2Na, and water) for 20 minutes at room temperature at a liquor:fi ber ratio of 1:1. The tresses were then rinsed for one minute under running water. One-half milliliter of a plain shampoo (15 wt% of sodium polyoxyethylene lauryl ether sulfate (2.5 E.O.) with 2 wt% N,N-bis(2-hydroxyethyl)- dodecanamide solution adjusted to pH7 with phosphoric acid) was applied to the wet hair tresses, which were massaged by hand for 30 seconds. The hair tresses were then rinsed for 30 seconds under running water. One-half milliliter of a plain conditioner (2 wt% SPDA, 0.5 wt% benzyl alcohol, 3.0 wt% stearyl alcohol, 0.6 wt% lactic acid, and water) was applied to the wet hair tresses and distributed manually for 30 seconds, then left on for one minute. The hair tresses were rinsed for 30 seconds under running water. The hair tresses were then towel dried, dried under a hot dryer for three minutes, and brushed 20 times. Mica in conditioner treatment. A fresh mica sheet was used as a model for the hydrophilic surface of alkaline-color-treated weathered hair. Mica sheets of approximately 10 × 10 × 0.1-mm were cleaved on both sides immediately prior to use. They were then immersed in a conditioner solution for one minute at 40°C. The mica sheets were then rinsed under running distilled water for 30 seconds and naturally dried. Chemicals. The investigators obtained 18-methyleicosanic acid (18-MEA), 19-methylei- cosanic acid (19-MEA), and stearoxypropyldimethylamine (SPDA) by chemical synthesis (16,17). Other chemicals were commercially available. METHODS Measurement of dynamic contact angles of hair. The wetting forces of hair were measured by the Wilhelmy method, using a K100MK2 tensiometer (Kruss). Single hair fi bers were scanned over 3 mm at a velocity of 2 mm/min for the advancing mode. Dynamic contact angles were calculated from where F is the wetting force, d is the diameter of the hair, γ is the surface tension of water, and θ is the contact angle of the fi ber surface. The hair fi ber diameter was measured on the transverse section of each fi ber with a rotating fi ber diameter measurement system equipped with a laser (Kato Tech Co.) at 20°C and relative humidity (RH) of 65%. The wetting force measurements were also performed at 20°C, 65% RH. Quantitative analysis of fatty acids. The amount of fatty acids absorbed to the hair fi ber was measured using liquid chromatography/mass spectrometry (LC-MS, Agilent Technolo- gies, Palo Alto, CA). Hair fi bers were immersed in chloroform/methanol (1:1 by volume) for one hour at room temperature. The extracts were dried using a nitrogen stream. The residues were then dissolved in chloroform/methanol (1:9 by volume). In the system, an F = d p g cosq

JOURNAL OF COSMETIC SCIENCE 512 1100 binary pump was connected to two mobile phases [M1, methanol/water (8:2 by volume) containing 100 mM ammonium acetate and 50 mM acetic acid and M2, meth- anol containing 100 mM ammonium acetate and 50 mM acetic acid] that were eluted at a fl ow rate of 0.2 ml/minute. The mobile phases were programmed consecutively, as fol- lows: a linear gradient of M1 100–0% (M2 0–100%) between 0 and 20 minutes, an iso- cratic elution of M1 0% (M2 100%) for 10 minutes, and an isocratic elution of M1 100% (M2 0%) from 30.1 to 40 minutes for column equilibrium (a total run time of 40 min- utes). The injection volume was 5 μl. The column (L-column ODS 2.1-mm inner diam- eter × 150 mm, Chemicals Evaluation and Research Institute, Tokyo, Japan) temperature was maintained at 40°C. ESI measurements in the mass spectrometer were performed with the following settings: polarity, negative heater temperature of nitrogen gas, 350°C fl ow of heated dry nitrogen gas, 11.0l/minute nebulizer gas pressure, 30 psi capillary voltage, −4000V fragmenter voltage, 200V. The selected ion monitoring (SIM) measure- ment in negative ion ESI was performed using unit mass resolution mode. To detect deprotonated ions for 18-MEA, 19-MEA, or n-HEA, m/z = 325.2 was monitored. Measurement of surface properties of mica by atomic force microscopy (AFM). AFM images of the adsorbed layer on the mica surfaces were obtained using a Nanoscope IIIa multi-mode AFM (Veeco Instruments, Santa Barbara, CA) with an E-scanner. Tapping mode imaging was used to obtain the topographic images of the adsorbed membrane layers. To ensure that imaging the membrane caused no damage, the tapping force was set at the lowest possible level. The nominal spring constants of the cantilevers are reported by the manu- facturer to be 20–100 N/m. All images presented in this work were obtained reproducibly over at least three spots on the sample surfaces. The images were acquired with a scan rate of either 0.5 or 1.0 Hz and were fl attened with a fi rst-order polynomial prior to analysis. The mechanical properties of the adsorbed membrane were analyzed by the AFM scratch- ing method (18–21). Scratching of the adsorbed membrane was performed in contact mode at a constant force, and a micro-fabricated tip made of silicon nitride (Si-N) and a cantilever, having a spring constant of 0.38 N/m, were used. First, an image (typically, 5 μm × 5 μm) of the adsorbed membrane was acquired then, a smaller area (typically 1 μm × 1 μm) was scanned while loading the hard tip onto the surface. Following this, the scanning was repeated over the larger area. This method is hereafter called “scratching.” Thus, if the absorbed layer was strongly bound to the surface, it was harder to remove. Measurements of the thicknesses of the adsorbed layers on the mica surfaces were ob- tained using a NanoScope V multi-mode AFM, equipped with an environment control cell, and the substrate temperature was controlled using a heating stage, which has been modifi ed to be programmable. First, the membrane thickness was measured at room temperature then, the temperature of the sample stage decreased at a rate of 1°C/minute to a temperature (25°C, 15°C, 5°C, 0°C, −5°C, and −10°C) where it was maintained for at least an hour. RESULTS AND DISCUSSION DYNAMIC CONTACT ANGLE MEASUREMENTS The contact angles of normal hair and alkaline-color-treated weathered hair are shown in Figure 2. The contact angle of normal hair was around 91.4° ± 4.6°, which means