Doctor of Philosophy (PhD)
Faculty of Science
This thesis aims to increase understanding of the relationship between molecular structure and liquid crystalline temperature range by exploring the effects of oxidation, thionation, and dimerization on the self-assembly and properties of novel discotic materials. First, two alkoxy-substituted dibenzanthracenequinones were prepared by oxidation of the corresponding dibenzanthracenes. The quinone induced a liquid crystalline phase in the hexaalkoxy dibenzanthracene derivative, but not in the tetralkoxy derivative. However, both of the resulting materials were un-reactive to any further synthetic modifications that could be used to improve their properties. In comparison, two heteroaromatic dithienoanthracenedicarboximides were successfully prepared, although the addition of the thiophene was not able to induce a columnar phase in these materials.
In contrast, the effect of thionation on self-assembly was explored via a series of thionated dibenzanthracenes and a series of thionated triphenylenes, both of which displayed broad columnar phases and increased aggregation in solution. In general, it was found that thionation allowed for tuning of the LUMO energy level without having a significant effect on the liquid crystalline temperature range of the material. These results, combined with the relative ease of the synthetic transformation, suggest that thionation may be a promising method for the design of novel electron-deficient liquid crystalline materials.
Finally, although the target discotic dimers could not be achieved, we were able to successfully synthesize the corresponding N-substituted alkylamine dibenzanthracenes and characterize their liquid crystalline behaviour. It was found that, when compared to the corresponding alkyl-substituted derivative, the exposed amine destabilized the liquid crystalline phase. The terminal amine was successfully converted to an acetyl group; although this was observed to lead to a stabilization of the crystalline phase and a narrowing of the liquid crystalline temperature range.
Overall, by characterizing both the self-assembly and photophysical properties of these materials, this thesis hopes to contribute to a better understanding of the intermolecular interactions occurring in this class of compounds and may, ultimately, help to develop materials that have future applications in organic electronics.
Psutka, Katie M., "The Effect of Oxidation, Thionation, and Dimerization on the Self-Assembly and Photophysical Properties of Novel Discotic Materials" (2018). Theses and Dissertations (Comprehensive). 2067.