Frustration in chiral nematic liquid crystal
Author
Al-Lawatiyah, Afaf Ali Juma
English abstract
The textural behaviour of a chiral-nematic material confined between two glass plates treated to induce homeotropic alignment is investigated. The parameters determining the textural behaviour of the specimen are the cell thickness, the twist and the penetration depth of the surface forces. As the temperature of the specimen is increased the strength of the twist of the material increases and the penetration depth of the surface forces decreases. Both effects contribute to favour the restoration of the helical structure in a specimen where the surface forces have imposed the homeotropic alignment. The specimen presented in this thesis displays a homeotropic-nematic texture at room temperature and a cholesteric texture at high temperature. In the temperature range corresponding to the critical value of the twist for the restoration of the helix an intermediate texture has been observed. In this phase circular bubble domains with the helical structure are formed. The evolution of these bubbles is studied. The nucleation and the evolution of the metastable textures observed by previous authors is investigated
