Skip to main content
Concentration, Temperature, and pH Dependence of Sunset-Yellow Aggregates in Aqueous Solutions: An X-Ray Investigation
Physical Review E
  • Leela Joshi, Kent State University - Kent Campus
  • Shin-Woong Kang, Chonbuk National University
  • Dena Mae Agra-Kooijman, Kent State University - Kent Campus
  • Satyendra Kumar, Kent State University - Kent Campus
Publication Date
Document Type
  • Chromonic Mesophases,
  • Liquid Crystals,
  • Surfactant,
  • Micelles,
  • Growth,
  • Behavior,
  • Systems,
  • Phase,
  • Dye

The dye sunset yellow (SY) forms columnar aggregates via π-π 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.


Copyright 2009 American Physical Society. Available on publisher's site at

Citation Information
Leela Joshi, Shin-Woong Kang, Dena Mae Agra-Kooijman and Satyendra Kumar. "Concentration, Temperature, and pH Dependence of Sunset-Yellow Aggregates in Aqueous Solutions: An X-Ray Investigation" Physical Review E Vol. 80 Iss. 4 (2009)
Available at: