Nonlinear optical and structural properties of new bent-core liquid crystal materials

Ibon Alonso Villanueva,

Univeristy of the Basque Country

This thesis supports some of the promising characteristics of banana or bent- core molecules as the building blocks of new mesogenic functional materials. It is divided into two main parts. The first one covers the study of new bent core materials. On the one hand, compounds containing azo or azoxy units and tetrathiafulvalene units. Not only do they have smectic and columnar mesophases whose structures are characterized by means of electron density maps deduced from X-ray diffraction intensities, but their photinduced effects are also studied (photoisomerization and photoconductivity). On the other hand, since their polar molecular arrangements make them suitable as nonlinear optical materials, second harmonic measurements are used to test these properties and it is shown how they can be greatly enhanced. The second part of the thesis is devoted to the study of two peculiar banana phases: the dark phase (optically isotropic), which is proposed as a new LCD mode, and the so-called B4 phase, whose local structure inside the TGB-like helix of smectic blocks is found to be antiferroelectric instead of ferroelectric.

Full Document