Search results for " liquid crystal"
showing 10 items of 100 documents
Electronic Properties of Discotic LC-Materials
1996
Abstract We have made extensive studies of the charge-carrier mobilities in the discotic hexagonal mesophases of triphenylene-based discotic liquid crystals. Using the time-of-flight technique, transient photocurrents were measured yielding charge-carrier mobilities for various electric fields and temperatures. Starting from promising results obtained with the monomeric discotic liquid crystalline model compound hexapentyloxytriphenylene (H5T), we synthesized a “discotic twin” with two triphenylene units linked together by a suitable spacer. Additionally, we synthesized a discotic liquid crystalline oligomer consisting of four triphenylene units which are bound to a flexible cyclosiloxane r…
Infrared absorption study of hexapentyloxytriphenylene A discotic liquid crystal
1993
Abstract Fourier transform infrared absorption (FTIR) spectroscopy has been used to study a discotic liquid crystal. IR spectra are reported as a function of temperature for hexapentyloxytriphenyle...
Fluoroalkylated discotic liquid crystals
1995
Abstract The concept of mesophase stabilization by partial fluorination of side chains has been extended to discotic systems. The mesophase structure is essentially unchanged, whereas the temperature range of the mesophase is strongly affected by the fluorinated side chains. Triphenylene substituted with only one partially fluorinated side chain exhibits a decrease of the clearing temperature, whereas for symmetrically substituted systems a broad range mesophase has been observed. This behaviour can be attributed to a segregation of the incompatible parts of the molecule giving rise to a stabilized columnar structure for the symmetrical substitution pattern.
A Columnar Liquid Crystal with Permanent Polar Order
2015
et al.
Monolayers and Langmuir-Blodgett Multilayers of Discotic Liquid Crystals?
2008
The field of monolayer and multilayer films of discotic LCs is at its very beginning. The scope and limitations of this preparation method have not yet been explored, and little is known about the structures obtainable. However, the potential access to extraordinary, ordered thin films is fascinating, and will stimulate research in the future.
Supramolecular control of liquid crystals by doping with halogen-bonding dyes
2017
Introducing photochromic or polymeric dopants into nematic liquid crystals is a well-established method to create stimuli-responsive photonic materials with the ability to "control light with light". Herein, we demonstrate a new material design concept by showing that specific supramolecular interactions between the host liquid crystal and the guest dopants enhance the optical performance of the doped liquid crystals. By varying the type and strength of the dopant-host interaction, the phase-transition temperature, the order parameter of the guest molecules, and the diffraction signal in response to interference irradiation, can be accurately engineered. Our concept points out the potential…
Photoresponsive Halogen-Bonded Liquid Crystals: The Role of Aromatic Fluorine Substitution
2019
A new strategy for controlling the liquid crystalline and photophysical properties of supramolecular mesogens assembled via halogen bonding is reported. Changing the degree of fluorination at the halogen-bond donor of the supramolecular liquid crystal allows for the fine-tuning of the halogen bond strength and thereby provides control over the temperature range of the mesophase. At least three fluorine atoms have to be present to ensure efficient polarization of the halogen-bond donor and the formation of a mesophase. In addition, it was found that stilbazole acceptors are superior to their azopyridine counterparts in promoting stable liquid crystalline phases. The halogen-bond-driven supra…
Mesogens with Aggregation-Induced Emission Formed by Hydrogen Bonding
2019
In this contribution, we report a supramolecular approach toward mesogens showing aggregation-induced emission (AIE). AIE-active aromatic thioethers, acting as hydrogen-bond donors, were combined with alkoxystilbazoles as hydrogen-bond acceptors. Upon self-assembly, hydrogen-bonded complexes with monotropic liquid crystalline behavior were obtained. In addition, it was found that the introduction of a chiral citronellyl side chain leads to drastic bathochromic shift of the emission, which was not observed for linear alkyl chains. The mesomorphic behavior, as well as the photophysical properties as a solid and in the mesophase of the liquid crystalline assemblies, were studied in detail.
Photo-switching and -cyclisation of hydrogen bonded liquid crystals based on resveratrol
2020
A series of hydrogen-bonded liquid crystals based on resveratrol and resveratrone is reported and investigated with respect to their photo-switchability (at 405 nm) and photo-cyclisation (at 300 nm).
Chiral mesophases of hydrogen-bonded liquid crystals
2020
The chiral induction in hydrogen-bonded liquid crystals is investigated. The experimental study was accompanied by detailed density functional theory calculations and variable-temperature solid-state deuteron NMR measurements indicating that interactions between the linking groups of the hydrogen-bond accepting unit play a key role in the chiral induction.