MOLECULAR FORCES IN PERMANENT WAVING 339 IMMERSION IN-- ':i 13E•:.I•I NI•TGAAF'TE i NH,•H50, .. ii:.:RoeSO:Li . , . .... ß •. .-.? .... .-':• .:. ..... : ::-.:. •- :• .'- - .! :• " i•- . ,• • ,. ß : Figure 6.--Relaxation of conventional permanent wave by immersion in various media. Hair tresses were waved by a conventional method involving processing with thioglycolate lotion for 15 min., water rinse, 30-min. wait and peroxide neu- tralization. Relaxation was produced by immersion and agitation in the follow- ing solutions: 0.15 Nammonium thioglycolate at pH 9 for 5 min. 0.5 N ammo- nium bisulfite at pH 6 for 20 min. 40% resorcinol for 15 min. 10 M lithium bromide at 80øC. for 15 min. lize or relax them by reaction with agents which rupture secondary bonds. Similarly if permanent waves produced by conventional reduction and re- oxidation of disulfides are presumed to be stabilized principally by disulfide cross links then it should be possible to destabilize them by treatment with agents which rupture disulfide groups but not with secondary bond breakers. An experiment was devised to examine the extent of curl re- laxation obtained after exposure to various media. Waved hair tresses were prepared by waving in an inert atmosphere for eighteen hours as described above in the preceding section and Fig. 5. Another set of tresses was prepared by a process simulating current commercial practice (second section, Fig. 2, left-hand tress). The hair tresses were then im- mersed and agitated in solutions which rupture disulfide bonds (0.5 M ammonium bisulfite at pH 6 for twenty minutes or 0.15 N ammonium thioglycolate at pH 9 for five minutes) or in nonreductive solutions of hydrogen bond breakers (40 per cent resorcinol for fifteen minutes or 10 M LiBr at 80øC. for fifteen minutes). After relaxation in these media, the hair tresses were washed vigorously and dried. The behavior of hair waved in the conventional manner with thioglycolate is shown in Fig. 6. It is clear that loss of curl follows relaxation in disulfide reducing agents but not after treatment with hydrogen bond breakers. In contrast is the behavior of hair waved in the inert atmosphere and stabilized by secondary bond rebuilding as shown in Fig. 7. Here substantial relaxation of curl is observed on treatment with the hydrogen bond breaking solutions whereas the reducing agents scarcely affect the wave level. It can therefore be concluded that stabilization of imparted curl can come about from the utilization either of covalent disulfide bonds or of the

340 JOURNAL OF THE SOCIETY OF COSMETIC CHEMISTS mAX AFTER IMMERSION IN- / : I:::: RESORCIN::Br:ILi .. .¾ . Figure 7. Relation of waves produced in an inert atmosphere. Hair tresses were waved in helium gas with thioglycolate lotion. Relaxation was produced by immersion and agitation in the following solutions: 0.15 N ammonium thioglycolate at pH 9 for 5 min. 0.5 N ammonium bisulfite at pH 6 for 20 min. 40% resorcinol for 15 min. 10 M lithium bromide at 80 ø C. for 15 min. secondary bonds that are present in hair. Which of these types of molec- ular forces are invoked will depend on the details of the process employed. WAVING IN THE ABSENCE OF REDUCING AGENT In view of some of the findings described above, it would seem natural to wonder whether waving can be accomplished through the use of secondary bond breaking agents alone, i.e. in the absence of reducing agent. Experi- ments conducted at room temperature with a variety of secondary bond breakers failed to demonstrate any kind of waving activity. At elevated temperatures, it was possible to show that some degree of waving was feasible. Figure 8 shows some of the results with potent solutions of hydrogen bond br,eakers. Immersion of hair on a rod in concentrated solutions of LiBr at 80øC. and slow d'ilution of the solution over a period of ':: .Li 8r HC, O NH• !t:': H2 NCON Figure 8.--Waving with solutions of secondary bond breakers. Hair tresses were wrapped on a rod 0.2 in. in diameter and immersed in sat- urated urea at 80øC. for 3 hr., 85% formamide at 100øC. for 10 min. or lithium bromide at 80øC. in the latter case the solution was 10 34 in- itially and water was added slowly to reduce the concentration to zero over 11/•. hr. The sulfhydryl content of the hair after treatment was 0.04 meq./gm. in all cases.