Melanin-mimetic multicolor and low-toxicity hair dye

Abstract

Most commercial permanent hair dyeing technologies are based on the oxidative process of p-phenylenediamine and its derivative materials. However, concerns about their toxicological issues have been raised throughout the years. Herein, we report an innovative surface coloration strategy for fabricating melanin-mimetic multicolor and low-toxicity hair dyes through sodium periodate-induced rapid deposition of eumelanin-like polydopamine (PDA) and pheomelanin-like PDA/cysteine co-deposited coatings on the hair surface. The color and morphology of the resulting hair were characterized in detail by several spectroscopy methods and the possible mechanism for the multi-coloring effects and structural differences of the melanin-mimetic coating was proposed. Our strategy eliminates the use of toxic dye precursors or organic solvents, and the favorable safety of the PDA-based formulations is demonstrated. The fabricated dyes can be applied to hair simply by combing, resulting in uniform multi-coloring effects within a short time. Furthermore, the melanin-mimetic hair dyes have excellent durability and ultraviolet protection performance. This work provides a facile and versatile methodology to develop the next generation of safe, sustainable and multicolor hair dyes and pave new avenues for advancing the field of surface coloration, nanoreactors, nanogenerators, energy storage materials and biomimetic sensing devices.

Fig. 1. Schematic of the preparation and coloring procedures of multicolor PDA coating-based hair dyes.

Fig. 2. Effect of reaction times, concentrations of SP and DA on (a) color and (b–e) UV-visible absorption properties of DA/SP solutions (DA solutions were diluted 60-fold before the spectral analysis). (f) SEM images of uncoated and PDA coated hair obtained at different reaction times.

Fig. 3. Photographical images (a) and lightness (b) of uncoated and PDA coated hair obtained at different reaction times, in comparison with another hair sample dyed with a commercial permanent black hair dye. UV transmittance (c) of uncoated and PDA coated hair obtained at different reaction times. Photos of PDA coated hair after 30 min deposition with different concentrations of (d) SP and (e) DA. The light-ness of PDA coated hair obtained using different concentrations of (f) SP and (g) DA, determined with a precision colorimeter.

Fig. 4. (A) ATR-FTIR spectra of uncoated quartz plate (curve a), PDA coatings oxidized by 0.1 wt% (curve b), 0.2 wt% (curve c) and 0.5 wt% (curve d) SP (DA concentration was 1.0 wt%) for 30 min; (B) ATR-FTIR spectra of PDA coatings synthesized with 0.1 wt% (curve a), 0.2 wt% (curve b) and 0.5 wt% (curve c) DA (SP concentration was 0.5 wt%) for 30 min.

Fig. 5. High-resolution C 1s XPS spectra of PDA coatings on hair surface synthesized with (a) 0.2 wt% SP, (b) 1.0 wt% SP (DA concentration was 1.0 wt%); (c) 0.1 wt% DA and (d) 0.5 wt% DA (SP concentration was 0.5 wt%) for 30 min.

Fig. 6. (a) The thermo-responsive phase transition property of PDA/PF127 hydrogel; (b) the hair dyeing process of PDA/PF127 hydrogel-based hair dyes.

Fig. 7. Photographical images of hair samples dyed with (a) commercial permanent black dye, (b) dark black-colored, (c) brown-colored and (d) light brown-colored PDA/PF127 based hair dyes before and after repeated shampoo washing. (e) The corresponding changes in lightness of each hair samples before and after exhaustive shampoo washing.

Fig. 8. (a) Photographical images and (c) color coordinate values of PDA/cysteine co-deposited hair obtained using different doping amounts of cysteine (DA concentration was 1.0 wt%). (b) Photographs and (d) color coordinate values of red-colored hair obtained through PDA/cysteine 1 : 2 co-deposition before and after repeated shampoo washing.