14 JOURNAL OF COSMETIC SCIENCE
Micro-beam X-ray
(5 J1 m)
Diffraction
Hair fiber: 50 -.,100 J1 m
Figure 2. SAXS experiment.
equal tilt to the hair axis. This diffraction pattern shows the same profile that was
estimated to diffract from the cuticle CMC in previous reports (6,7).
A one-dimensional intensity profile produced from the diffraction pattern is demon-
strated in Figure 3. The intensity {I(S) x S4} was plotted versus reciprocal spacing (S)
according to an analytical method proposed by Ohta et al. (7). Reciprocal spacing (S) was
used to represent the index for the distance from the center of the diffraction pattern,
where S =1/d =(2/A) x sin(20/2), with A representing the wavelength of the X-ray, 20
the scattering angle, and d the repeat distance. Using this method, we estimated the
thickness of the �- and 8-layers in the CMC. The region of S 0.2 shown in Figure 3
contains four peaks of I(S) x S4 .The spans of the peaks differed among the hair samples,
which reflected differences in CMC structure. All intensity profiles analyzed in the
present study contained at least three peaks of I(S) x S4 in the region of S 0.2. The
analytical region (S 0.2) was considered wide enough for correct estimation of the
thickness of the �- and 8-layers.
EFFECTS OF SOL VENT EXTRACTION ON CMC STRUCTURE
SAXS experiments were performed using hair samples extracted with the four solvents.
The estimated values of thickness of the �- and 8-layers differed, based on the solvent
used, as shown in Figure 4. The thickness of the �-layer was decreased by extraction with
acetone and hexane, while it was not changed by extraction with methanol or chloro-
form/methanol. In addition, the thickness of the 8-layer was decreased by extraction

CMC STRUCTURE IN HAIR CUTICLE 15
0.020
�
0.015
rJJ
X
,.-.__0.010
rJJ
0.005
0
0 0.05 0.10 0.15 0.20
Figure 3. One-dimensional equatorial profile extracted from SAXS pattern, obtained as shown in Figure 2.
We estimated the thickness of the 13- and a-layers from the one-dimensional equatorial profile according
to the method of Ohta et al. (7), using the following formula: l(S) x S4 =a x {cos[TI x S x (13 +o)}}2 x
{sin(TI x S x l3)} 2 ,where S is reciprocal spacing [=(2/A)sin(20/2)} and I is intensity.
with methanol, acetone, and chloroform/methanol, and did not significantly change
with hexane.
The relationships between the CMC structure and extent of hair dyeing are shown in
Figure 5. The average values for the extent of hair dyeing (�E) with each of the
treatments shown in Figure 1 were plotted with the average values of thickness of the
�- and o-layers shown in Figure 4. There was a significant correlation between the extent
of hair dyeing and the thickness of the o-layer, whereas no correlation was seen between
the extent of hair dyeing and the thickness of the �-layer.
DISCUSSION
Using a micro beam X-ray method, we observed the CMC structure without the prestain-
ing or slicing of hair fibers under typical ambient conditions (30°C, 50% relative humidity).
We considered that the present SAXS technique was able to obtain information regard-
ing hair structure under natural conditions, as the hair samples did not require prestain-
ing. Structurai changes in rhe cmicle CMC weie found to be Giuscd by extraction .vith
the various solvents, which seemed to reflect their hydrophobicity. Methanol, which has