STRUCTURAL ANALYSIS OF PERMANENT WAVED HAIR BY SAXS 127 the permed hair with these treatments. As a result, the difference in IFs orientation found between the convex and concave side of the stretched SLS-immersed hairs were narrowed. DISCUSSION The distance between IFs was found to be larger in permed hair compared with bleached hair. This is believed to be because of changes in intermolecular bonds, including disul- fi de bonds, due to the chemicals used in perming. Furthermore, on comparing the convex and concave sides of permed hair, the FWHM were found to be signifi cantly larger on the convex side. This is possibly because IFs exist in different orientations on the concave and convex sides, as it is wrapped around the rod. According to previous research on naturally curly hair using SAXS, lack of homogeneity in IF orientation between the convex and concave sides of the curl plays a major role in affecting hair curl morphology (10). In case of permed hair, anisotropic IF orientation between the convex and concave sides of the curl seemed to be similarly related to macroscopic hair curl. Figure 4. Distance between IFs and FWHM for bleached hair and permed hair. 1: Mean values for the cortex of bleached hair. 2: Mean values for the convex curvature side of permed hair. 3: Mean values for the concave curvature side of permed hair. t-test was used for statistical analysis with *p 0.05, **p 0.01, ***p 0.001. Figure 5. Distance between IFs and FWHM for permed hair and stretched hair. Black fi lled square convex sides and gray fi lled square concave side. t-test was used for statistical analysis with *p 0.05, **p 0.01, ***p 0.001.

JOURNAL OF COSMETIC SCIENCE 128 It was observed that curl diameter effi ciency of the stretched hair, SLS-immersed hair, and stretched SLS-immersed hair was signifi cantly lower than that of permed hair. Therefore, the changes in microstructure that occur when a permed curl falls out are discussed. First, stretched hair was compared with permed hair. No differences were present in the distances between IFs, whereas FWHM of stretched hair was signifi cantly smaller than that of permed hair. A previous study reported that the sliding of keratin molecule along the IF axis when the hair was stretched (15). It was considered that the stretched treat- ment affected leading IF orientation by causing it to become isotropic. Subsequently, comparison of SLS-immersed hair and permed hair revealed that the dis- tance between IFs in SLS-immersed hair was signifi cantly smaller than that of permed hair. In addition, FWHM in the convex side of the curl in SLS-immersed hair was signifi - cantly smaller than that in permed hair. Therefore, SLS immersion affected leading IF orienta- tion by causing it to become isotropic. Concerning the distance between IFs, it was thought a possibility that the fl ow-out or swelling of Intermediate fi lament associated protein (IFAP) occurred in SLS immersion. Concerning the FWHM, a hypothesis was substantiated in Figure 6. Distance between IFs and FWHM for permed hair and SLS immersed hair. Black fi lled square convex sides and gray fi lled square concave side. t-test was used for statistical analysis with *p 0.05, **p 0.01, ***p 0.001. F igure 7. Distance between IFs and FWHM for permed hair and stretched SLS-immersed hair. Black fi lled square convex sides and gray fi lled square concave side. t-test was used for statistical analysis with *p 0.05, **p 0.01, ***p 0.001.