Date of Award
Chemistry and Biochemistry
Loeb, Stephen J.(Chemistry and Biochemistry)
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This thesis presents design, synthesis and characterization of a range of new liquid crystalline interlocked molecules and to study structure-property relationships between rotaxane design and mesomorphism. Chapter 1 introduces concepts of supramolecular chemistry and liquid crystals and cooperative effect between rotaxane and liquid crystals towards functional molecular machines. In Chapter 2, a systematic approach to introduce liquid crystallinity into the 1,2-bis(pyridinium)ethane/DB24C8 motif is described. The chapter begins with synthesis and purification of dumbbells (without macrocycle) and rotaxanes (with macrocycle) substituted with purely aliphatic extended 3,5-disubstituted stoppers with increasing alkyl chain length. Chapter continues with phase characterization and structure-property relationships between dumbbells and rotaxanes. The dodecane chain was sufficiently fluid to induce smectic mesomorphism in both the dumbbell and rotaxane, with rotaxane forming SmA phase by POM and XRD analysis. Chapter 3 presents an extension to Chapter 2 with the addition of longer straight chain and branching aliphatic chains to our 1,2-bis(pyridinium)ethane/DB24C8 rotaxane motif to study structure-property relationships and phase characteristics. The ability of the side-chain to self-organized showed large differences in phase behaviour. The pentadecane straight chain extended rotaxane exhibited a unidentified mesophase, the hexadecane straight chain rotaxane showed SmA mesomorphism, the branched hexadecane and the hyperbranched rotaxanes both showed lamellar soft crystal phases. Chapter 4 describes the effect of applying groups typical for low molecular weight LCs (siloxanes) to our 1,2-bis(pyridinium)ethane/DB24C8 motif and a modified rotaxane design based on a bis(oxymethylbenzylpyridinium)ethane/DB24C8 motif. The structure-property relations between both systems, and in comparison with the dodecane chain substituted systems, are presented. The new design revealed SmC mesophases for both the dodecane and siloxane substituted rotaxanes. Chapter 5 focuses on the introduction of chirality into the siloxane substituted rotaxane with SmC mesomorphism presented in Chapter 4. Chirality was introduced via a chiral anion as well as incorporation of a chiral crown. Observations to changes in the superstructure from the incorporation of chirality is addressed. The chiral anion exchanged rotaxane showed SmC* mesomorphism and the chiral crown rotaxane showed SmX* mesomorphism. Chapter 6 presents the design and synthesis of a molecular shuttle based upon the structure-property relations determined from the previous chapters.
Suhan, Natalie, "New Liquid Crystalline Rotaxanes" (2009). Electronic Theses and Dissertations. 399.