Date of Award
© 2014 Benjamin R. Mercado. All rights reserved. Access to this work is restricted to users within the Swarthmore College network and may only be used for non-commercial, educational, and research purposes. Sharing with users outside of the Swarthmore College network is expressly prohibited. For all other uses, including reproduction and distribution, please contact the copyright holder.
Bachelor of Arts
Chemistry & Biochemistry
Peter J. Collings
In this research I have studied the assembly equilibria and kinetics of the infrared laser dye IR-806 at concentrations below the liquid crystal phase. Using UV-vis spectroscopy I determined that there is a significant isosbestic point present at about 722 nm as assembly occurs with incremental changes in temperature at a single concentration of IR-806. This indicates that all assembly sizes are electronically similar in solution. In addition, it was determined from UV-vis that the assembly process is extremely cooperative with a change in ∆H of the growth step of -65.3 ± 0.9 kJ/mol. In addition, a stopped-flow kinetics apparatus at the Fox Chase Cancer Center in Philadelphia, PA was used to assess the kinetics of assembly and disassembly. Assembly was examined by quickly adding NaCl to a solution of IR-806 and disassembly was investigated by a sudden 1:10 dilution with water. While the assembly kinetics proved difficult to analyze, the disassembly kinetics yielded an interesting "two-part" kinetics curve where two rate constants were clearly visible. The slower rate constant yielded a linear Arrhenius plot with Eₐ = 48.2 ± 0.2 kJ/mol. All experimental data were compared to the cooperative model for assembly known as nucleation and growth. This model was consistent in all noticeable ways with both the equilibrium and kinetics data. Through further analysis of the kinetics data in tandem with the absorption data showing the isosbestic point, I conclude that nucleation and growth is a viable model for this assembly process though other models are not entirely ruled out.
Mercado, Benjamin R. , '14, "Thermodynamic and Kinetic Characteristics of Assembly in the Chromonic Liquid Crystal IR-806" (2014). Senior Theses, Projects, and Awards. 214.