Liquid crystal films confined between patterned substrates.

In this thesis, systems of nematic liquid crystals confined between patterned substrates have been studied using molecular computer simulation. The aim of this work, done in parallel with experimentalists in Leeds, has been to investigate the use of chemical patterning as a novel method for controlling liquid crystal alignment. In the first part of this thesis, the study of confined systems of liquid crystalline particles has been addressed. Using the hard needle wall and hard gaussian overlap potentials, homeotropic and planar alignment of model molecules on the substrates has been induced. We have then extended the study of confined liquid crystals systems from the use of unpatterned symmetric susbtrates systems to hybrid anchored systems and, finally, to a system involving one patterned substrate. The results from this initial study show that surface anchoring can be controlled by changing the surface interaction parameter and that, by varying the surface interaction parameter across a model substrate, a pattern can be imposed on the confining surfaces.In the second part of this thesis, the substrate model developed in our initial stripe systems is used to simulate liquid crystal films confined between two identical patterned substrates. This is achieved through a comprehensive investigation of stripe patterned systems. In this, we show that, by varying key parameters like the stripe width, the surface interaction parameters and the film thickness, surface patterning can be used to control the polar anchoring angle and set the azimuthal anchoring. Our results show that a full range of tilt angles can be obtained by changing these key parameters.Following this work on striped systems, we extend our study to 2D patterned substrates (i.e. square and rectangle patterns). Here, the results show that by changing two key parameters, the surface interaction parameter and the shape of the pattern, it is possible to gain more complete control of the bulk tilt angle as the latter variesmonotonically as the key parameters are changed. We close the thesis with brief descriptions of some other substrate patternings that have been considered in this thesis work. These include circle and displaced/rotated stripe systems. We then draw some conclusions and comment on possible directions for future work.