Date of Award
© 2018 Timothy Ogolla. All rights reserved. This work is freely available courtesy of the author. It may only be used for non-commercial, educational, and research purposes. For all other uses, including reproduction and distribution, please contact the copyright holder.
Bachelor of Arts
Chemistry & Biochemistry
Peter J. Collings
The antihistamine, disodium cromoglycate (DSCG), forms a nematic (N) phase in which the molecules are stacked like a pile of cards to form columnar assemblies; addition of a small amount of chiral molecules can form a chiral nematic (N*) phase, with the assemblies arranged around a helical axis. For thermotropic liquid crystals (TLCs) the pitch is usually measured using the Cano wedge method, and in lyotropic chromonic liquid crystals (LCLCs) the fingerprint texture is typically used. The effect of a dopant on the pitch of a chiral LCLC is quantified using the helical twisting power, which is the slope of the plot of inverse pitch versus dopant concentration. Previously in the Collings group, the Cano method was used to measure the pitch and HTP of various dopants. So, in this work the fingerprint method was used to confirm the validity of the Cano wedge results. A comparison shows that the results from both methods are consistent, and so both are acceptable ways to measure the pitch of chiral LCLCs. In addition, the temperature dependence of the pitch is investigated, to understand the nature of the interaction between the chiral dopant and the chromonic assemblies. The results indicate that the chiral interaction is much more sensitive, to changes in temperature as the transition temperature, Tₘ, is approached, than the assembly size and number density.
Ogolla, Timothy , '18, "Pitch Measurements in a Chiral Lyotropic Chromonic Liquid Crystal: Temperature and Dopant Concentration Dependence of the Pitch" (2018). Senior Theses, Projects, and Awards. 233.
Available for download on Wednesday, January 01, 2025