[Soft Matter Café] Dye-surfactant interactions and their implication on hair dyeing

Surfactants are an important component of commercial hair dyeing formulations, which renders it crucial to understand their interaction with hair dye molecules to facilitate a systematic formulation design. Knowledge about the driving forces for dye-surfactant interaction can be obtained by identifying the location of dye molecules in surfactant micelles. A combination of NMR-spectroscopy and contrast matching in small-angle neutron scattering was successfully employed for this purpose. The complementary use of both techniques permitted to unambiguously identify the location of dye molecules in DTAB micelles. It was furthermore used to discern the solubilisation locus of dye molecules in micelles of the non-ionic surfactant C12E5 as a function of the pH of the dye-surfactant solution. In the course of the presentation, the co-assembly of dye with DTAB and with C12E5 and its implication on hair dyeing is discussed. In addition to that, the feasibility of SANS contrast matching for the localisation of dye molecules in micelles of low molecular weight surfactant is demonstrated.

Soft Matter 19, 4579–4587 (2023) | Soft Matter 19, 4588–4598 (2023) | Nanoscale Advances 5, 5367–5384 (2023).

About the speaker: Wenke Müller graduated from the University of Potsdam in Germany with a master’s degree in chemistry and is now completing her PhD-thesis with the title “Solution behaviour of dissociative direct dyes in the presence of surfactants” at the Institute Laue-Langevin (France) in collaboration with the University of Paderborn (Germany) and the company KAO Germany GmbH (Germany).