Properties of the uniaxial and biaxial nematic phases of the dodecyltrimethylammonium bromide/1-dodecanol/water lyotropic mixture including azo dye and drug molecules

ABSTRACT

Lyotropic nematic phase properties of novel mixtures of dodecyltrimethylammonium bromide (DTMABr)/1-dodecanol (DDeOH)/water, doping with anionic azo dyes (amaranth and tartrazine) and a drug molecule disodium cromoglycate (cromolyn, DSCG), were investigated. The textures of the uniaxial and biaxial nematic phases were observed by polarizing optical microscopy (POM). Uniaxial-to-biaxial nematic phase transitions were determined from the temperature dependence of the birefringences via laser conoscopy. Partial phase diagrams of the mixtures were constructed as a function of concentrations of dyes and drug molecules by combining the POM and laser conoscopy results. Small-angle X-ray scattering (SAXS) was performed to evaluate micellar structure parameters. The results indicate that those dyes and drug molecules have a greater effect on (a) the nematic-nematic phase transition temperatures, (b) the biaxial-nematic phase-domain range in the partial phase diagrams, and (c) micelle-shape anisotropy, comparing to the addition of other conventional inorganic electrolyte ions. Furthermore, dye and drug molecules may be sequenced in the Hofmeister series of ions, considering the number of ionic groups in their molecular structures and also the chaotropic and/or kosmotropic degrees of the ionic groups. Since these molecules may have a resonance structure (e.g. DSCG), as a result of the existence of the aromatic parts in their structures, this resonance structure should be considered to investigate their effects on the stabilization of the lyotropic nematic phases.

KEYWORDS:

• Lyotropic nematic phases
• biaxial phase
• nematic-nematic phase transitions
• surfactant-dye/drug interactions
• birefringences
• partial phase diagram
• polarizing optical microscopy
• laser conoscopy

Acknowledgements

Erol Akpinar (EA) and Antonio M. F. Neto (AMFN) designed the experimental parts of the studies, then analyzed and discussed the results. EA and Merve Tabak performed the experimental work. SAXS data analysis and discussions were performed by AMFN and Dennys Reis.

Disclosure statement

No potential conflict of interest was reported by the author(s).

Correction Statement

This article has been corrected with minor changes. These changes do not impact the academic content of the article.

Additional information

Funding

This work was supported by Bolu Abant Izzet Baysal University Directorate of Research Projects: [Grant Number 2022.03.03.1555]; The National Council for Scientific and Technological Development (CNPq): [Grant Number 465259/2014-6]; The São Paulo Research Foundation (FAPESP: [Grant Number 2014/50983-3; 2016/24531-3]; The Scientific and Technological Research Council of Turkey (TÜBİTAK): [Grant Number 120Z721].