Analysis of IR-806 Aggregation and Chromonic Liquid Crystal Properties
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2011
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Swarthmore College. Dept. of Physics & Astronomy
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Thesis (B.A.)
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Abstract
IR-S06 is an infrared absorbing chromonic liquid crystal that forms a liquid crystal phase
at around 0.45 wt% at room temperature. It has a unique coexistence region whereby
there is not ever a distinct separation of phase between the isotropic liquid and liquid crystal
regions, only a decrease in birefringence everywhere. Also, IR-S06's most stable conformation
(in gas form) was obtained, and it was found to be most stable in its AA conformation.
Unfortunately, it was discovered that IR-S06 is not stable in solution, quickly degrading in
acidic environments, and not completely stable in any aqueous environment. The decay
times of a 0.0005 wt% solution were 21 ± 1.6 hours at pH 2.S and lOS ± 1.6 hours at pH
7.3. It is least stable at low concentrations, but was also found to degrade in solution at
liquid crystal phase concentrations.
IR-S06 exhibits a very dynamic absorption spectra, with three distinct peaks that vary
in amplitude depending on concentration. These peaks can be connected to the formation
of different aggregate species in solution as concentration changes. Analysis of these peaks
support the idea that there is a distinct structural change between the aggregates before the
liquid crystal phase. Analysis of the low concentration peak amplitude (or monomer peak)
allowed for a calculation of stacking free energy change. IR-S06 was found to have a stacking
free energy change of 9.01 ± 0.12 kET.
Although it may not have long term applications due to its instability in solution, IR-S06
might be able to shed light on how other chromonics aggregate at concentrations lower than
their liquid crystal phase. This report discusses the investigation of such chromonic and
liquid crystal properties not only with the purpose of learning more about IR-S06, but also
of applying this insight to other chromonic liquid crystals.