Chemical Bonds and Hair Behavior: A Review

This review examines the role of various chemical bonds in determining hair behavior, focusing on the mechanical properties of hair fibers. Hair is composed of keratin proteins, stabilized by hydrophobic interactions, hydrogen bonds, salt bridges, disulfide bonds, and isodipeptide bridges. Disulfide bonds significantly influence hair's elasticity, especially in wet conditions, as shown by stress–strain curves for natural and chemically treated hair. The review also discusses how treatments like bleaching and perming affect these bonds. The findings suggest that disulfide bonds are crucial for maintaining hair's structural integrity under wet conditions, while other bonds contribute under dry conditions.