Towards Aqueous Nanostructures Based on Oligo(aniline)s

Abstract

Oligo(aniline)s are the ideal replacement of poly(aniline), as they exhibit the same optoelectronic properties and oxidation states, however, with excellent solubility, processability and switchability between different oxidation states. In addition, oligo(aniline)s provide a great platform to design and synthesize tunable and well-defined supramolecular structures and potentially even new functions. In this thesis, a family of cationic amphiphiles based on oligo(aniline) was synthesised. The aim of this thesis is to provide tunable and switchable self-assembled structures of our oligo(aniline) based amphiphiles using an addressable packing parameter approach. Two architectures, single-tailed and bola-type cationic TANI-based amphiphiles, were designed, allowing a comparison between the two. Moreover, the head groups were varied to include quaternary amines and quaternary phosphines. The prepared amphiphiles were characterised using NMR spectroscopy, MS spectrometry, and elemental analysis. The self-assembled structures of the prepared oligo(aniline) amphiphiles in the EB state, TANI functionalised with pentyl trimethylphosphonium amphiphiles (TANI-PTPB), TANI functionalised on both sides with pentyl trimethylammonium amphiphiles (TANI-(PTAB)2), and TANI functionalised on both sides with pentyl trimethylphosphonium amphiphiles (TANI-(PTPB)2), were investigated in detail and elucidated by atomic force microscopy, electron microscopy, small-angle x-ray scattering, and small-angle neutron scattering studies. The variations of head group sizes and structures were found to contribute to alterations in the self-assembling morphologies. These changes in morphology, from fibrous structures to vesicles, highlight the important role of packing parameter ( 𝒑 = 𝒗 / 𝒂𝟎𝒍𝒄 ). In other words, an increase of the headgroup’s size results in a decrease in the packing parameter, causing the morphology to change. A variety of dopants with different volumes and structures were found to increase the volume of the hydrophobic core, causing the packing parameter to increase as a consequence. The variations of the packing parameter promote various self-assembled structures, fibrous, chainlike structures, worm and spherical structures. These variations boost the role of the packing parameter to construct an avenue of well-defined and tunable structures for oligo(aniline)-based amphiphiles. Oligo(aniline) amphiphiles present an elegant and simple route to switchable and tunable functional materials. This work provides promising routes for applications in drug delivery.