title: Large assembly formation via a two-step process in a chromonic liquid crystal.
abstract: IR-806 is a near-infrared cyanine dye that forms assemblies in aqueous solutions which in turn orientationally order into a liquid crystal phase at concentrations as low as 0.5 wt %. Unlike many chromonic liquid crystals, the absorption spectrum of IR-806 changes dramatically with concentration, showing an isodesmic assembly process at lower concentrations followed by a second process at higher concentrations that is not isodesmic. The lower concentration assembly process is characterized by a free energy change per molecule of about 9 k(B)T, not unlike other chromonic systems. However, X-ray scattering measurements suggest that the assemblies that form during the higher concentration process are much larger than what is observed for many chromonic liquid crystals. Although there is a transitional region between the liquid crystal and isotropic phases of 10-15 °C, unlike most chromonic liquid crystals, no biphasic region is observed using polarizing microscopy.
authors.affiliation: Department of Physics & Astronomy, Swarthmore College, Swarthmore, Pennsylvania 19081, USA.
authors.forename: Elizabeth A
authors.initials: EA
authors.lastname: Mills
authors.forename: Margaret H
authors.initials: MH
authors.lastname: Regan
authors.forename: Vesna
authors.initials: V
authors.lastname: Stanic
authors.forename: Peter J
authors.initials: PJ
authors.lastname: Collings
mesh_terms: D002867:Chromones / Q000737:chemistry*; D018360:Crystallography, X-Ray; D012542:Scattering, Radiation
chemical_list: D002867:Chromones