Date of Award

Spring 2013

Document Type

Restricted Thesis

Terms of Use

© 2013 Kenny Nieser. 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.

Degree Name

Bachelor of Arts

Department

Physics & Astronomy Department

First Advisor

Peter J. Collings

Abstract

Benzopurpurin 4B (BPP) and IR-806 are both dyes that form a chromonic liquid crystal phase at very low concentrations in solution, around 0.35-0.45 wt%. Despite the low concentration, these molecules form assemblies that become large and numerous enough to orientationally order. In previous research of IR-806, the change in the absorption spectra across different concentrations led to the suggestion of a two-stage assembly process of the structures forming the liquid crystal phase. Above a threshold concentration, still below the liquid crystal transition concentration, a sharp change in the dominant absorption peak indicated that a new structure was forming.

Using kinetics, we were able to verify this threshold concentration above which large assemblies of intermediate assemblies begin to form in IR-806 and discover a similar threshold behavior in BPP. After diluting a sample, we record the subsequent change in the absorbance at a chosen wavelength to follow the disassembly process.

We also found that under certain conditions, the addition of NaCl to a sample promoted assembly formation. Thus, we recorded changes in absorbance at a chosen wavelength after the mixing of NaCl in our sample to follow the self-assembly process. We found the disassembly process to occur at an approximately exponential rate, depending on the initial concentration of the sample. As the concentration of the sample increased, the disassembly process was slower, indicating a more complicated assembly had formed which required a longer time to break down. We used an assembly model from protein assembly kinetics known as the Finke-Watzky mechanism to fit our results from assembly data. The Finke-Watzky model fit our data well and showed that an increase in the salt concentration added to our sample caused the assembly process to proceed faster.

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