Abstract
Photosensitive liquid crystals represent an important class of functional materials that experience rapid development. Hereby, we present novel bent-core liquid crystals bearing a lateral substitution on the central core and in the vicinity of the photosensitive unit—an azo group. The azo group enables fast (E)-to-(Z)-isomerization upon irradiation with UV-light and visible light, while the substitution facilitates the high stability of the photochemically formed (Z)-isomer. The effectiveness of the irradiation and the composition of photostationary states was determined by UV/Vis and 1H NMR spectroscopy. A nematic phase formed by the materials was characterized by differential scanning calorimetry and optical polarizing microscopy. We show that the materials easily change their relative configuration of the N=N double bond not only in solution, but also in the mesophase, which leads to fast isothermal phase transition from the nematic phase to isotropic liquid.
Highlights
Thermotropic liquid crystals (LCs) are well-known for their unique ability to selfassemble and form long-range ordered structures, so-called mesophases between anisotropic solid and isotropic liquid states
We focused on focused a group on of Bent-core liquid crystals (BCLCs) possessing the in azo group in elongating one of the elongating
The sequence of phases and phase transition temperatures of materials inthe thefluorinated fluorinated (Ia)-d were determined by observations of characteristic textures and their changes in a polarizing optical microscope (POM) NIKON Elipse E600Pol (Nikon, Tokyo, Japan) and checked by differential scanning calorimetry (DSC) and a Perkin-Elmer 8000 (Perkin-Elmer, Waltham, MA, USA) calorimeter was utilized on the cooling and heating runs at a rate of 5 K min−1
Summary
Thermotropic liquid crystals (LCs) are well-known for their unique ability to selfassemble and form long-range ordered structures, so-called mesophases between anisotropic solid and isotropic liquid states. Isomerization, triggered by an external light source of a specific wavelength, results in changes of geometry and breaks the supramolecular arrangement within a mesophase This typically leads to the decrease of order parameter of the system and the transition from a mesophase into the isotropic liquid, followed by visible light-triggered and/or thermal relaxation into the original state [9,10,11]. Multicomponent mixtures containing azobenzene-based benzene-based LCs can be utilized [16] The properties of such materials can be modLCs can be utilized [16]. Bent-core liquid crystals (BCLCs) are an extraordinary class of the mesomorphic maBent-core liquid crystals (BCLCs) are an extraordinary class of the mesomorphic terials since they may exhibit polar order and macroscopic chirality in self-assembled materials since they may exhibit polar order and macroscopic chirality in self-assembled mesophases consisting of achiral molecules.
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