791849-97-3Relevant academic research and scientific papers
Photo and electrically switchable behavior of azobenzene containing pendant bent-core liquid crystalline polymers
Srinivasan, M. Vijay,Kannan,Roy
, p. 936 - 946 (2013/03/28)
New class of photo and electrically switchable azobenzene containing pendant bent-core liquid crystalline monomers (AZBM 1, 2, and 3) and their polymers (AZBP 1, 2, and 3) are reported. The synthesized precursors, monomers, and polymers were characterized by FT-IR, 1H, and 13C NMR spectroscopy. Thermal stability of polymers was examined by thermogravimetric analysis and revealed stable up to 260 °C. The mesophase transition of monomers and polymers are observed through polarized optical microscopy (POM) and further confirmed by differential scanning calorimetry (DSC). The electrically switching property of monomers and their polymers were studied by electro-optical method. Among the three monomers AZBM 1, 2, and 3, AZBM 1 and 2 exhibit antiferroelectric (AF) switching and AZBM 3 exhibits ferroelectric (F) switching behavior. On the other hand, low molecular weight polymers (AZMP 1, 2, and 3) show weak AF and F switching behavior. The photo-switching properties of bent-core azo polymers are investigated using UV-vis spectroscopy, trans to cis isomerization occurs around 25 s for AZBP-1 and 30 s for AZBP-2 and 3 in chloroform, whereas reverse processes take place around 80 and 90 s.
Laterally substituted symmetric and nonsymmetric salicylideneimine-based bent-core mesogens
Findeisen-Tandel, Sonja,Weissflog, Wolfgang,Baumeister, Ute,Pelzl, Gerhard,Shreenivasa Murthy,Yelamaggad, Channabasaveshwar V.
supporting information; experimental part, p. 129 - 154 (2012/02/15)
Bent-core mesogens have gained considerable importance due to their ability to form new mesophases with unusual properties. Relationships between the chemical structure of bent-core molecules and the type and physical properties of the formed mesophases a
Novel supramolecular side-chain banana-shaped liquid crystalline polymers containing covalent- and hydrogen-bonded bent cores
Wang, Ling-Yung,Tsai, Hsin-Yi,Lin, Hong-Cheu
experimental part, p. 1277 - 1288 (2011/10/01)
Novel supramolecular side-chain banana-shaped liquid crystalline (LC) polymer complexes AmBn-N bearing various (m/n) molar ratios of hydrogen- and covalent-bonded bent-core components were acquired by the free radical polymerization, where the hydrogen-bonded (H-bonded) structures were executed via mixing equimolar portions of proton donor (H-donor) polymers AmBn (homopolymers/ copolymers) and pyridyl proton acceptor (H-acceptor) bent cores (small molecules). The influences of the molar ratios of bent-core H-bonded components in side-chain banana-shaped LC polymers and their corresponding polymer complexes on mesomorphic and electro-optical properties were first investigated, The voltage-dependent antiferroelectric properties of spontaneous polarization (Ps) values in the polar smectic phase of the supramolecular side-chain banana-shaped copolymers were also reported. The nematic and tilted smectic phases were verified by XRD measurements, and the SmCP phase was further confirmed by the triangular wave method. Surprisingly, a novel enantiotropic polar smectic (SmCPA) phase was generated in some bent-core side-chain polymer complexes AmBn-N. Therefore, a special approach to constructing (or stabilizing) the SmCP phase was first developed in this study by copolymerization of bent-core covalent- and H-bonded units in side-chain polymer complexes (with proper m/n molar ratios of 16/1 and 10/1) from both bent-core covalent- and H-bonded monomers (i.e., B and A-N units, respectively) without the SmCP phase.
Bent-core liquid crystal (LC) decorated gold nanoclusters: Synthesis, self-assembly, and effects in mixtures with bent-core LC hosts
Marx, Vanessa M.,Girgis, Hidy,Heiney, Paul A.,Hegmann, Torsten
supporting information; experimental part, p. 2983 - 2994 (2010/02/27)
We present the first synthesis of a series of thiol-, thioacetate-, and xanthate-terminated bent-core derivatives, as well as the preparation of gold nanoclusters using the thiol-terminated bent-core compounds. The mesomorphic properties of the bent-core compounds have been investigated by polarizing optical microscopy (POM), differential scanning calorimetry (DSC), small angle X-ray scattering (SAXS), and electro-optic tests. From this series, the mono-xanthate derivatives form rectangular or hexagonal columnar phases, and the mono-thiol derivative with shorter alkyl chains forms a metastable, likely smectic, phase. All other bent-core compounds and intermediates exclusively form disordered or multi-layer lamellar crystalline solid modifications. High-resolution transmission electron microscopy (HR-TEM) images of the bent-core functionalized gold nanoclusters prepared from the thiol-terminated derivatives, taken after slow evaporation of the solvent, provide evidence for the formation of self-assembled nanocluster arrays. Upon dispersion of these gold nanoclusters in two structurally related bent-core LC hosts (one forming a SmCPA, and the second with a terminal double bond displaying a Colr phase), a shift in the surface plasmon resonance was observed indicating a LC host-dependent aggregation of the nanoparticles. Finally, we report initial results on the effects of different concentrations of these nanoclusters on the thermal properties as well as the applied voltage/current response of the parent SmCPA host.
Ten isomeric five-ring bent-core mesogens: The influence of the direction of the carboxyl connecting groups on the mesophase behaviour
Wolssflog, Wolfgang,Naumann, Gisela,Kosata, Bedrich,Schroeder, Martin W.,Eremin, Alexey,Diele, Siegmar,Vakhovskaya, Zinaida,Kresse, Horst,Friedemann, Rudolf,Ananda Rama Krishnan,Pelzl, Gerhard
, p. 4328 - 4337 (2007/10/03)
In order to study the role of the direction of the connecting groups in bent-core mesogens we synthesized two series of ten possible achiral isomeric five-ring bent-core compounds in which all aromatic rings are connected by ester groups and each of which possesses the same length of the terminal chains (octyloxy or dodecyloxy, respectively). The structure of the isomers is distinguished by the direction of at least one ester group, only. The mesophase behaviour of the compounds has been studied by polarizing microscopy, differential scanning calorimetry, X-ray experiments and electro-optical measurements. We have found that in spite of the minor structural differences a variety of mesophases occur (SmCPA, Colrec, Col ob) whereby the clearing temperatures vary from 121 to 193 °C (octyloxy isomers) and 112 to 189 °C (dodecyloxy isomers). Depending on the direction of the ester groups some of these isomers show interesting properties, such as field-induced inversion of chirality in SmCPA and columnar phases, the field-induced enhancement of the clearing temperature, a second-order phase transition Colob → SmCPA or the reversible field-induced phase transition Colob → SmCP P. The unexpectedly strong influence of the direction of the connecting groups is discussed on the base of theoretical calculations and molecular dynamics simulation on isolated molecules. The Royal Society of Chemistry 2005.
Influence of a fluorine substituent on the mesomorphic properties of unsymmetrical five-ring bent-core compounds
Murthy, H.N. Shreenivasa,Sadashiva
, p. 2813 - 2821 (2007/10/03)
The synthesis and mesomorphic properties of unsymmetrical five-ring bent-core compounds containing a fluorine substituent in one of the arms are reported. A comparison of the properties with the symmetrical compounds having two fluorine substituents indic
