Concentration, temperature, andpHdependence of sunset-yellow aggregates in aqueous solutions: An x-ray investigation

Abstract

The dye sunset yellow (SY) forms columnar aggregates via pi-pi stacking in aqueous solutions. These aggregates develop orientational and translational order at elevated concentrations to exhibit the nematic (N) and columnar (C) mesophases. Positional-order correlation lengths of the aggregates in the directions parallel and perpendicular to the stacking direction were measured as functions of temperature, concentration, and ionic content of solutions with synchrotron x-ray scattering in magnetically aligned samples. Average length of aggregates (i.e., the number of SY molecules in an aggregate) grows monotonically with concentration while their effective transverse separation decreases. The scission energy, E , determined from the Arrhenius thermal evolution of the longitudinal correlation length, is found to be 4.3+/-0.3 kBT and 3.5+/-0.2 kBT , in the N and C phases, respectively. Temperature and concentration dependence of E suggests that chromonic aggregation is not an isodesmic process. The aggregate length decreases with decreasing pH when HCl is added to the solution.

NMR Investigations of the Interaction Between the Azo-Dye Sunset Yellow and Fluorophenol

“…30,31 Bulk parameters, such as diffusion coefficients, have also been demonstrated to be useful. 22,32,33 In this study, a combination of both diffusion measurements and changes in the chemical shift of the 19 F moiety on the probe molecule are used to probe the interaction between of fluorophenol isomers with sunset yellow assemblies.…”

“…15,16 The aggregation behaviour of sunset yellow FCF (SSY, sodium (E)-6-hydroxy-5-((4-sulfonatophenyl) diazenyl) naphthalene-2-sulfonate) in both isotropic solution and its liquid crystal phases has been well studied using a variety of techniques, including xray, [17][18][19] optical scattering 18 and NMR spectroscopy. [20][21][22] The association is widely thought to be head-to-tail stacking of the monomer units with a slight twist, typical of H-type aggregation.…”

Influence of Structural Isomerism and Fluorine Atom Substitution on the Self-Association of Naphthoic Acid

“…Previously we have utilised NMR spectroscopy to investigate the selfaggregation of the azo-dye sunset yellow as a function of concentration. 28 This wellstudied system 3,[10][11][12][13]25 provided an ideal demonstration of the utility of NMR spectroscopy for the investigation of aromatic self-aggregation. More recently, we have explored the interaction of a structurally similar small probe molecule with sunset yellow.…”

“…17 Multicomponent systems are also important, probing the role of functional groups in aggregation [18][19][20] and drug delivery. [21][22][23][24] A number of physical techniques can provide information on aggregation processes such as optical absorption, 3 x-ray scattering 3,13,25,26 and nuclear magnetic resonance (NMR) spectroscopy. 10,12,[26][27][28] In general, absorption and scattering based experiments provide information on the bulk properties of a sample, e.g.…”

Aligning lyotropic liquid crystals with silicon oxides

“…Understanding lyotropic liquid crystal alignment configuration is essential, [5,6] and achieving a reproducible and reliable alignment becomes necessary for a number of applications related to biological materials that require the use of aqueous solutions, [7][8][9] especially in the context of chip-onglass. [10] The subject become even more pressing considering that even slight changes in the morphology and oxide content are known to drastically affect the hydrophilicity of the silicon oxide thin films, [11] which depending on the deposition technology employed can show moderate to high hydrophilicity with contact angles with pure water varying between almost 80 and less than 10 degrees.…”