Self-Assembled Liquid Crystal Nanostructures

Self-assembly of liquid crystalline molecules has been a highly interesting research area over
the past few decades. The modification of traditional rod-like liquid crystalline molecules by
adding additional functional groups is an effective way to obtain novel liquid crystal phases
due to the segregation of incompatible molecular components, and this has been proved by
various mesophases obtained from molecules which possess special shapes and structures.
More recently, liquid crystalline molecules have been introduced to functionalize metallic
nanoparticles to arrange these spherical particles into ordered structures. In this case, liquid
crystalline molecules are grafted onto the surfaces of nanoparticles and the strong selfassembly
ability of the molecules is the driving force for the ordered arrangement of
nanoparticles. This method opens a new way to build spherical nanoparticles into
untraditional nanostructures. Gold nanoparticles, due to their potential of building
metamaterials that possess novel optical properties, such as negative refractive index and
tunable surface plasmon resonance, is of great interest in this field of research.
In this thesis, the self-assembly behaviour of a number of T-shaped liquid crystalline
molecules have been investigated by small angle X-ray scattering (SAXS) and grazing
incidence small angle X-ray scattering (GISAXS) methods and some complicated liquid
crystal phases formed by T-shaped bolaamphiphiles have been solved. These T-shaped liquid
crystalline molecules, each of which is composed of a biphenyl core ended by two terminal
polar groups and a relatively long lateral chain, were found to form several novel structures
which have never been realized in any liquid crystalline systems reported before.
Using the same experimental methods, the self-assembled nanostructures of liquid crystalline
molecules functionalized gold nanoparticles (GNPs) were also investigated. Different ordered
superlattice structures including both 2D and 3D ones have been obtained from these hybrid
systems. The results show how the mode of self-assembly of gold nanoparticles can be
controlled by changing the parameters of coating molecules.
Electron density maps of these structures were reconstructed using the diffraction intensities
obtained from experimental results. The corresponding model of each structure was also
proposed based on the reconstructed electron density maps as well as the structures and
dimensions of molecules. Moreover, some simulation work was conducted, for example
diffraction intensity simulation, diffraction pattern simulation and molecular dynamic
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simulation, and good agreements between experimental and simulation results have been
achieved.
Finally, with the help of GISAXS technique the morphologies of double layers of gold
nanoparticles prepared via layer-by-layer fabrication method have been investigated. By
carefully adjusting the distance between adjacent gold nanoparticle layers, a successful
control of the coupling of the localized surface plasmon polariton resonance was reported
recently. In this thesis the sideway correlation of gold nanoparticles and the correlation
between two gold nanoparticle layers were studied. The features observed in GISAXS
patterns can be interpreted very well with relatively simple models.