Date of Award
Doctor of Philosophy (PhD)
Chemistry & Biochemistry
David M Walba
Three different projects are described, in which target molecules are synthesized based on specific functional goals: electromechanical response, bent-core phase formation, and charge transport behavior. The bulk properties of these materials are then characterized with respect to these goals.
The first project entails the synthesis and characterization of several variations on W317, a calamitic liquid crystal with a strong electroclinic effect. Alpha, omega-diene analogues of this molecule were synthesized and reacted via ADMET into a main-chain polymer, with the goal of creating electromechanical actuators. To improve the bulk strength and macroscopic response of the polymers, attempts were made at cross-linking, including co-polymerization with a unit containing pendant cinnamate groups, or by mixing with a compound containing two benzophenone units linked by a tether. An analogue of W317 containing a thiol at one end and an alkene at the other was synthesized and polymerized in-cell by UV light.
In the second project, several homologues of W513 were synthesized and characterized. W513 is known to be an extremely rare example of a bent-core molecule that exhibits the B4 phase, yet does not contain a Schiff base. Seven n-alkyl-tailed homologues were synthesized and all of them exhibit the B4 phase, but interestingly, their behavior and stability in other bent-core phases (particularly the B1) varied widely. In addition, two perfluoroether-tailed versions and an alpha-methyl branched alkyl-tailed version were synthesized, none of which exhibited any bent-core phases.
The third project involved the synthesis of a library of materials for use as liquid crystal organic photovoltaics. This library consisted of oligothiophenes containing between three and six rings joined at the alpha positions, with two terminal tails consisting of either alkoxymethyl groups or perfluoroetheroxymethyl groups. Investigations are still ongoing regarding charge-transport behavior in these compounds.
Richardson, Jacqueline Mae, "Liquid Crystals for Functional Nanomaterials: Electroclinic Artificial Muscle Polymers, Nanorods from Achiral Bent-Core Mesogens, and Thiophenic Photovoltaics" (2010). Chemistry & Biochemistry Graduate Theses & Dissertations. 27.