ADHESION FAILURE IN HAIR 369 Figure 19. Adhesion failure from alternating treatments with anionic and cationic surfactants on previously permed hair (1). Photographs reproduced with permission of Springer-Verlag. insoluble complex with the sorbed cationic surfactant (Figure 21). After several repeti­ tive anionic-cationic reactions, buildup of a hydrophobic anionic-cationic complex oc­ curs, producing adhesion failure at this site. These reactions will produce beta­ membrane failure rather than beta-delta failure (see Figure 11). The fact that scale lifting occurs from the reaction ofTGA-treated hair more readily than with bleached hair suggests that this effect is governed more by reaction with the thioester linkage than with the disulfide grouping. Nevertheless, the net effect is to weaken the CMC and increase its tendency to fail under stress. SUMMARY AND CONCLUSIONS Although adhesion failure in hair fibers can occur inside cuticle and cortical cells, it frequently occurs in the cell membrane complex (CMC), often involving interlayer bonding. Therefore, a model of the CMC is presented, based on prior research in which we propose interconnecting bonds between the different layers to assist in our interpre­ tation of hair fracturing mechanisms for cuticle chipping, deep transverse cuticle cracks,

370 JOURNAL OF COSMETIC SCIENCE \ J ...,Peptide, Hydrogen g' Bonds & Salt Links 00dl8 ° ° 0 .£._..peptide Bonds and van der Waals ---van der Waals S-CH2-C02- f=0 f=O =0 \ 1 Peptide, Hydrogen �Bonds & Salt Links oo�o 0 00 0 0 0 �eptide Bonds � and van der Waals � � � � f --¥an der Waals C=O f=O f=O _ "s-CH2-C02- � Figure 20. Reactions of the thioester linkage with TGA in the upper beta layer. \ J ...,Peptide, Hydrogen "7' Bonds & Salt Links oon s 0 OQ (1 Q .£._.peptide Bonds and van der Waats ---van der Waals S-CH2-C02- r=0 r=O =0 J Yeptide, Hydrogen -----::::::,.,,'Bonds & Salt Links oon s 0 OOry o�eptideBonds and van der Waals �an der Waals ._- ... ... .. ...----_rJ•.1•.• .. -. Figure 21. Reactions of thioester with TGA followed by quat & anionic in this same layer. cracks during heat drying, scale lifting by surfactants, and catastrophic failure. Failure in the wet state generally involves hydrophilic layers (endocuticle or the contact zone of the CMC) or bonding between hydrophilic layers, whereas failure in the dry state