Hair perming via thiol-Michael click reaction: A strategy to avoid oxidative damage.

Abstract

Objectives: Oxidative agents used in conventional hair perming damage hair fibres. This study proposes a novel perming approach employing 1,4-butylenediamine bismaleimide (1,4-BB) as a cross linking agent via thiol-Michael click chemistry to avoid oxidative harm. The perming performance and effects on hair fibre properties were investigated and compared.

Methods: 1,4-BB was synthesized via an acylation reaction and evaluated for cytotoxicity using the MTT assay. Perming efficiency was compared on reduced hair cross linked by 3 wt% H₂O₂, 6 wt% NaBrO₃ and 0.5 wt% 1,4-BB, respectively. Chemical changes during different perming methods were analysed via Raman spectroscopy, fluorescence microscopy, XRD and FT-IR characterization. Perming efficiency and durability were evaluated and explained by calculating the -SH connection ratio via X-ray photoelectron spectroscopy. Mechanical properties, colour and surface properties of hair samples permed by different methods were evaluated and compared.

Results: 1,4-BB was successfully prepared and exhibited no cytotoxicity over a wide concentration range. Click perming using 1,4-BB exhibited comparable perming efficiency and superior durability compared to oxidative perming methods. Higher α-helix keratin content and reduced sulfonate formation contributed to the preservation of hair mechanical properties. Click perming also benefited from the preservation of hair colour and surface properties, including morphology and hydrophobicity.

Conclusion: Thiol-Michael click perming offers a non-oxidative alternative with reduced hair damage and enhanced perming durability.