We propose a method of prediction for hair breakage induced by change of molecular structure. The changes inside hair by cyclical extension were investigated using infrared (IR) spectroscopy coupled with multivariate curve resolution (MCR) and two-dimensional correlation spectroscopy (2D-COS). In bleached hair, cyclical extension stresses at 5% strain levels were seen to increase the signal of CH2 and that of component primarily derived from C=O at 55 cycles, SO3H signal at 75 cycles, ultimately leading to fiber breakage. The CH2 profile of bleached hair significantly increased at 55 cycles compared to before extension in almost agreement with component profile primarily derived from C=O. This agreement behavior was likely to surface translocation of the lipids such as wax esters and triacylglycerols inside hair caused by cyclical extension. Two-dimensional correlation spectra indicated that SO3H was produced by way of a cystine oxide by cyclical extension. In contrast, only CH2 signal gradually increased without breakage in untreated hair. Thus, the method proposed in this study monitoring three functional groups is expected to have potential application in prediction of hair breakage by cyclical extension such as everyday grooming actions.
Keywords: Cyclical extension; Hair; Infrared spectroscopy; Multivariate curve resolution; Structural change; Two-dimensional correlation spectroscopy.
© 2022. The Author(s), under exclusive licence to The Japan Society for Analytical Chemistry.