Self-assembly of stimuli-responsive supramolecular nanostructures based on oligo(aniline) amphiphiles

Student thesis: Doctoral ThesisDoctor of Philosophy (PhD)

Abstract

Self-assembly is a valuable tool for the preparation of functional, supramolecular nanostructures from the bottom up. Liquid crystal mesophases are particularly attractive in this regard, with complex nanostructures that are readily adaptable to a diverse range of applications, from drug delivery vesicles to templates. Meanwhile, oligo(aniline)s are conjugated oligomers, with exciting switchable conductive and oxidative properties that can both benefit from and be used to direct self-assembled structures.
In this thesis, the effect of electroactive amphiphiles on the formation of monoolein cubic phases is explored and explained through discussion of their molecular packing parameters. Subsequently, an understanding of the ordered mesophases formed by a combination of amphiphiles and monoolein is used in the formation of well-defined, nanostructured polymers.
The preparation of single-tailed and bola-form tetra(aniline)-derived amphiphiles is described, with similar but chemically distinct structures chosen to provide different molecular packing parameters. The amphiphilic nature of the molecules, with their tetra(aniline) cores and alkyl tails terminated by cationic head groups, enabled their interaction with lipid bilayers. Small-angle X-ray scattering and UV-Vis/NIR absorption spectroscopy were used to probe the assemblies formed by the combinations of amphiphiles and lipids, which showed that transitions between cubic phases could be readily controlled by tuning of the amphiphiles’ oxidation states and structures.
Different approaches for the synthesis of a polymerizable tetra(aniline)-derived amphiphile are also described, although with limited success owing to the formation of unwanted side products, which could not be removed by typical purification techniques. Instead, the binding of tetra(aniline)-amphiphiles is achieved through electrostatic interactions, using acids with multiple doping groups to non-covalently cross-link the amphiphiles in solution and within lipid cubic phases.
The facile manipulation of lipidic mesophases with electroactive amphiphiles is promising for the design of responsive architectures for many applications, while explorations of the templated assembly of oligo(aniline)s should guide further research into the design of responsive, porous polymers.
Date of Award28 Sep 2021
Original languageEnglish
Awarding Institution
  • The University of Bristol
SupervisorAnnela M Seddon (Supervisor) & Charl F J Faul (Supervisor)

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