Structure and dynamics of nematic phases with strong smectic fluctuations formed by bent-core mesogens

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Mesophases with mesogens of non-cylindrical shapes exhibit remarkable complex structures and, in some phases, a very fast electro-optical response.Enhanced polar and smectic fluctuations, driven by steric interactions of bent mesogens, for instance, result in the formation of cluster phases with strong susceptibility to external fields. Such highly responsive materials have broad perspectives for applications. The shape of the mesogens can also be controlled by external stimuli such as light in photoisomerisable molecules. This proposal is based on the extensive collaboration between our group in Magdeburg and the Department of Organic Chemistry at Martin Luther University Halle (C. Tschierske and M. Alaasar). The proposal's primary aim is to investigate the effects of the photo-tuneable nanostructures on liquid crystals' micro and macroscopical properties in bulk and restricted geometry. We propose to study complex liquid crystalline systems such as photoswitchable mesogens forming nematic, twist-bend nematic phase, bent-core smectic phases with the heliconical nanostructure, and the newly discovered polar nematic phase.The central questions are how the nanostructure of the mesophase and photo-stimulation affect the bulk and surface properties of liquid crystals, how it affects the behaviour of colloids based on such materials. We will study the behaviour of liquid crystals in bulk, in droplets and filaments as well. The proposed research will be conducted in five stages, starting with the characterisation of the bulk properties and shifting the focus to the studies of light-driven anchoring transitions in pure photoswitchable compounds and systems with photoswitchable surfaces only. We will employ the acquired knowledge for understanding the behaviour of the solid inclusions in an LC matrix. The translational and rotational motions of colloidal particles will be investigated in the nematic, twist-bend nematic and ferroelectric nematic phases. At the final stage, we will explore the dynamics of liquid crystal filaments with photoismerisable mesogens. The output of this research will elucidate the mechanisms underlying the interplay between the light-driven mesogenic shape changes, structure formation and the properties of the novel liquid crystalline systems.