Proceedings PaperControlling order with light and light with order in liquid crystals: Two case studies (Conference Presentation)
This presentation comprises two topics, both relating to the interplay of light and order in liquid-crystalline (LC) materials. Firstly, we will present a novel series of azobenzene-based, halogen-bonded supramolecular LCs, with rich photochemical phenomena and exhibiting both reversible photochemical crystal-to-isotropic and LC-to-isotropic phase transitions. Simultaneous analysis of light-induced changes in birefringence, absorption, and optical scattering allowed us to conclude that less than 4 % of the mesogenic units in the cis-form suffices to trigger the LC-to-isotropic phase transition. To the best of our knowledge, this is the first quantitative analysis of the phase transition process in supramolecular liquid crystals, demonstrating the versatility of these materials as functional liquid-crystalline assemblies and pinpointing their potential towards building supramolecular actuators. Secondly, we propose a conceptually novel approach to enhance the orientational optical nonlinearity of dye-doped LCs, based on polymer stabilization. Compared to azobenzene-triggered photochemical systems, photophysical systems, where the alignment change is caused by light-induced torques due to absorbing moieties, may provide some benefits, allowing for molecular reorientation only above certain threshold intensity, and reducing reorientation instabilities and fluctuations in the photostationary state. In addition to decreasing the light intensity at which self-phase modulation takes place, the polymer stabilization approach may open up a pathway towards all-optical realization of temporally stable photonic elements and guided-wave structures based on LC systems.