From Fundamental Self-Assembly Studies to Applications in Everyday Life: The Formation of a Supramolecular Shampoo

Amino acid-based surfactants are promising ingredients for cosmetic formulations, combining mildness with intrinsic self-assembly properties. A recent challenge in the cosmetic field is the replacement of synthetic polymers, used as rheological modifiers, with sustainable and biodegradable alternatives. In this work, sodium cocoyl glycinate (SCG) and sodium cocoyl alaninate (SCA) were investigated as both surfactants and supramolecular gelators for the development of a "supramolecular shampoo". pK_a analysis and rheological studies revealed that SCG forms robust gel networks at pH 5, whereas SCA shows limited stability. The progressive incorporation of typical cosmetic ingredients, including cocamidopropyl betaine (CAPB), preservatives, conditioning agents, and fragrance, led to a controlled decrease in mechanical strength while preserving pseudoplastic behavior. The final formulation remained stable under accelerated aging and freeze-thaw conditions for months. These results demonstrate that supramolecular structuring offers a viable and sustainable alternative to conventional polymer-based systems in shampoo formulations.