Interactions between diester amide Gemini surfactants and polymers, and their application in hair dyes

In this study, the interaction between a diester amide Gemini surfactant (C12–E2Ph–C12) and the non-ionic polymer polyethylene glycol (PEG) with average molecular weights of 6000 g mol−1 and 10,000 g mol−1 was investigated using the surface tension method. The study showed no discernible interaction between them. Further examinations, using surface tension, micropolarity and turbidity methods were conducted to investigate the interaction between C12–E2Ph–C12 and the anionic polymer sodium alginate (NaAlg). C12–E2Ph–C12 and NaAlg molecules bind together to form aggregates with a pearl necklace-like structure, driven by electrostatic attraction. This interaction is evident in both the surface tension and micropolarity curves, where double plateaus appear. The inorganic salt NaCl exhibited a dual influence on the interaction between C12–E2Ph–C12 and NaAlg, manifesting as either salt enhancement or reduction, depending on their competitive effects. Additionally, the dyeing performance of the different surfactants on two types of dyes was investigated using a colorimeter. C12–E2Ph–C12 showed favorable effects on dyeing uniformity, color fastness, and improvement of hair tensile strength. Hair dyeing results were satisfactory when C12–E2Ph–C12 was included as a uniform coloring agent and NaAlg was used as a thickening agent in the hair dye formulation.