Effect of the surfactant head-group size dependence of the dye-surfactant interactions on the lyotropic uniaxial to biaxial nematic phase transitions

• Published in: Journal of molecular liquids Vol. 332; p. 115842
• Main Authors: Akpinar, Erol, Uygur, Nazli, Ordu, Oznur Demir, Reis, Dennys, Neto, Antônio Martins Figueiredo
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 15.06.2021
• Subjects: Anionic azo dye Sunset Yellow; Laser conoscopy; Lyotropic uniaxial and biaxial nematic phases; Polarizing optical microscopy; Small-angle X-ray scattering; Surfactant-dye interaction; Surfactant-dye interaction; Polarizing optical microscopy; Lyotropic uniaxial and biaxial nematic phases; Anionic azo dye Sunset Yellow; Laser conoscopy; Small-angle X-ray scattering
• ISSN: 0167-7322; 1873-3166
• DOI: 10.1016/j.molliq.2021.115842

In the present study, the interactions of the anionic azo dye Sunset Yellow with dodecylalkylammonium bromide (DAABr) surfactants in lyotropic mixtures have been investigated for the stabilization of the different lyotropic nematic phases. Sunset Yellow doped mixtures of DAABr surfactants, with different head-group size, were studied by polarizing optical microscopy, laser conoscopy, and small-angle X-ray scattering. It was found that the extent of the interaction of Sunset Yellow with DAABr surfactant head groups on micelle surfaces affects the stabilization of different nematic phases, by causing the change in the micellar structural parameters. The results also indicated that the micelle surface curvature should be different in the three nematic phases. [Display omitted] •Extent of surfactant-dye interactions affects the stabilization of nematic phases.•Surfactant head group size is crucial for the stabilization of nematic phases.•Micelle surface curvature should be different in the three nematic phases.