A new silyl terminated bent-core mesogen was synthesized which shows a randomly tilted SmCR phase and a columnar phase with p2gg lattice as new modes of self-assembly in this class of compounds.
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Calamitic and discotic liquid crystalline phases for mesogens with triangular cores.
Soft Matter
September 2019
University of Warsaw, Faculty of Chemistry, ul. Żwirki I Wigury 101, 02-089 Warsaw, Poland.
Mesogenic compounds having new triangular mesogenic cores containing salicylaldimine and enaminocarbonyl or barbituric moieties have been synthesized and their liquid crystalline, dielectric and optical properties have been studied. Appropriate substitution of such cores with various numbers of lateral chains (alkoxy, perfluorinated or polyether) leads to mesogens forming either lamellar (SmC), nematic or columnar (Colhd and Colho) phases. Some of the materials show an unusual phase sequence with a re-entrant isotropic phase appearing below the columnar (Colhd) phase; others form two columnar hexagonal phases with a weakly first order transition between them.
View Article and Find Full Text PDFThermal behavior and high- and low-temperature phase structures of gemini fluorocarbon/hydrocarbon diblocks.
Langmuir
April 2013
Systèmes Organisés Fluorés à Finalités Thérapeutiques (SOFFT), Institut Charles Sadron (ICS, UPR CNRS 22), Université de Strasbourg, 23 rue du Loess, BP 84047, 67034 Strasbourg Cedex 2, France.
The thermal behavior and phase structure of two series of gemini fluorocarbon/hydrocarbon diblock amphiphiles with the general formula (CnF2n+1CH2)(Cm - 2H2m - 3)CH-CH(CnF2n+1CH2)(Cm - 2H2m - 3), with n = 8, 10 and m = 6, 12, 14, 16, 18, 20 (abbreviated as di(FnHm)), have been investigated by differential scanning calorimetry, polarized optical and freeze-fracture transmission electron microscopies, dilatometry, and small-angle X-ray scattering (SAXS). The various terms of the series exhibit the same thermal behavior, essentially composed of two exothermal transitions, a low-temperature event that corresponds to the melting of the hydrocarbon chains at TH and a high-temperature transition associated with the melting of the fluorocarbon chains at TF. Below TH, a disordered plastic rotator phase, MLT, and above TH, a lamellar phase, MHT, were determined by SAXS experiments.
View Article and Find Full Text PDFInfluence of flexible spacers on liquid-crystalline self-assembly of T-shaped bolaamphiphiles.
J Am Chem Soc
May 2011
Department of Chemistry, Key Laboratory of Medicinal Chemistry for Natural Resources (Ministry of Education), Yunnan University, Kunming, Yunnan 650091, P. R. China.
T-shaped bolaamphiphiles composed of a biphenyl rigid core, a semiperfluorinated lateral chain, two polar 1,2-diol groups in the terminal positions and flexible alkyl spacers connecting the polar groups with the biphenyl core have been synthesized and investigated by polarizing microscopy, DSC and X-ray scattering. The influence of spacer length and position of the spacer on the self-assembly in liquid-crystalline phases was studied. A series of four different columnar phases (Col(hex)/p6mm, Col(rec)/p2gg, Col(squ)/p4gm and Col(squ)/p4mm), representing liquid-crystalline honeycomb structures composed of cylinders having hexagonal, pentagonal, and square cross section, were found on increasing the spacer length.
View Article and Find Full Text PDFCounterion effects on the columnar mesophases of triphenylene-substituted [18]crown-6 ethers: is flatter better?
Chemistry
June 2010
Institut für Organische Chemie der Universität Stuttgart, Pfaffenwaldring 55, 70569 Stuttgart, Germany.
The twisted lateral tetraalkyloxy ortho-terphenyl units in dibenzo[18]crown-6 ethers 1a-f were readily converted into the flat tetraalkyloxytriphenylene systems 2a-f by oxidative cyclization with FeCl(3) in nitromethane. Reactions of the latter with potassium salts gave complexes KX.2, which displayed mesomorphic properties.
View Article and Find Full Text PDFSelf-assembly of bent-core liquid crystals: formation of a modulated smectic phase with p2gg lattice to escape anticlinic tilt.
Chem Commun (Camb)
July 2009
Martin-Luther University Halle-Wittenberg, Institute of Chemistry Organic Chemistry, Kurt-Mothes Str. 2, D-06120 Halle, Germany.
A new silyl terminated bent-core mesogen was synthesized which shows a randomly tilted SmCR phase and a columnar phase with p2gg lattice as new modes of self-assembly in this class of compounds.
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