Effective Penetration of the Oxidized Keratin‐Rebonding Materials Into Hair Shafts Based on Charge Conversion

The study explores a novel approach to enhance the penetration of hair-rebonding materials into damaged hair shafts by using β-carboxylic acid amide moieties that convert from negative to positive charges under mild acidification. This charge conversion facilitates deeper penetration of the rebonding agents, specifically in the compound CTA2-BADG, which showed the most effective restoration of hair surface morphology and improved tensile strength. The effectiveness of this approach was confirmed through various analytical techniques, suggesting that charge-conversion chemistry is a promising method for delivering cationic bioactive agents into the interior of damaged hair.