Verhalten einer optisch anisotropen Schmelze als stationäre Phase in der Gas‐Flüssigkeits‐Verteilungschromatographie

Kelker, H.

doi:10.1002/bbpc.19630670714

Cited by 85 publications

(18 citation statements)

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“…The use of liquid crystals as stationary phases in gas-liquid chromatography was first reported by Kelker [11,12] and Dewar et al [13]. Liquid crystalline stationary phases in capillary columns are advantageous because of the combination of the shape-selectivity of the stationary phase with the efficiency of the capillary column [14].…”

Section: Analytical Properties Of Liquid Crystal Bmentioning

confidence: 99%

HPLC study of the intramolecular cyclization of a new nematogenic molecule. The gas chromatographic properties of the resulting liquid crystal

Saidat

Guermouche²,

Canlet

et al. 2002

Chromatographia

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SummaryThe internal cyclization of a new phenylcliazene liquid crystal (called A), with an activated methylene group in the ortho position to the cliazo linkage, has been studied. The kinetics of cyclization were studied at different temperatures and followed by HPLC. Separations were performed on a 30cm• silica column with n-heptane-tetrahyclrofuran-acetonitrile, 190:20:5 (v/v), as mobile phase. The Van't Hoff plot (of In reaction constant kagainst 1000/7) gives a mean activation energy of 101.3 • 2.1 kJ mol 1. The analytical properties of A and the final compound B during the decomposition were investigated by gas chromatography on home-made glass capillary columns coated with A. The retention times of the solutes tested became constant when the B/A ratio reached 5, which corresponds to 83% cyclization. The nematic phase of B has interesting properties enabling the separation of the isomers of clecalin, the positional isomers of cliethylbenzenes and phenols, and some polyaromatic hydrocarbons and their clerivatives.

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Section: Analytical Properties Of Liquid Crystal Bmentioning

confidence: 99%

HPLC study of the intramolecular cyclization of a new nematogenic molecule. The gas chromatographic properties of the resulting liquid crystal

Saidat

Guermouche²,

Canlet

et al. 2002

Chromatographia

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“…In 1963, Kelker was the first who used p, p′-azoxyphenetol as stationary phase in gas chromatography for separating the hydrocarbon isomers. According to Kelker, nematic phase of LCs has higher efficiency for the separation of isomers than the other phases of LCs [11]. Witkiewicz (1989) found that the mesophase selectivity shown by LCs based on Schiff base is a consequence of higher order when compared with liquids, and it is dependent on several factors including molecular shape, polarity and the flexibility of the solute molecule [4].…”

Section: Introductionmentioning

confidence: 99%

“…Methods for the preparation of LCs and their utilisation as stationary phases in gas chromatography columns have been developed [8][9][10][11][12][13][14][15][16]. In his work, Benalia et al [12] compared the gas chromatographic behaviour of three monomeric LCs that have the same basic structure (1,3,4-oxadiazole ring) but have different substituents.…”

Section: Introductionmentioning

confidence: 99%

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Synthesis and powder X-ray diffraction of new Schiff-base liquid crystal

Ghanem

Al-Hariri

2013

Liquid Crystals Today

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Liquid crystals (LCs) are soft materials that combine the fluidity of disordered liquids and the long-range orientational or positional order of crystalline solids, along one or two directions of space. A search for better stationary phases, including highly selective ones, is an important trend in chromatography development. Among the stationary phases under investigation are LC stationary phases that have been recently generated much interest. A variety of isomeric molecules were separated with high accuracy. Successfully, X-ray scattering is widely used to investigate and characterise the microscopic structure of most LCs. In this paper, a new liquid crystalline material that can be used potentially as stationary phase in gas chromatography was synthesised and characterised by means of nuclear magnetic resonance (NMR), infrared (IR) spectra, elemental analysis and X-ray diffraction.Keywords: liquid crystalline; Schiff base; nematic; X-ray diffraction; gas chromatography Introduction Liquid crystals (LCs) or mesophases are intermediate states of condensed matter; they combine long-range positional or orientational order along some directions of space (like in a crystal) and liquid-like disorder along other directions [1]. The most commonly obtained liquid crystalline phases are those with organic molecules or in solutions of surfactants.Presently, LCs can be divided into two categories: thermotropic and lyotropic according to the principal means of destroying the order in the parent solid state, probably thermotropic LC is the most widely studied category. Thermotropic LCs are formed by varying the temperature of the compounds and can be further classified as nematic (N) and smectic (S m ) structures [2,3].Since 1974, a number of studies have been centred on liquid crystalline materials with anisotropic properties. In particular, nematic LC materials based on Schiff base core have attracted considerable interest due to their unique solvent properties and potential applications in gas chromatography [4,5,[8][9][10][11][12][13][14][15][16].Increasing attention has been focused on important pollutants and phenols introduced into the environment through the discharge of industrial waste and the decomposition of various pesticides and herbicides [5][6][7]. The determination of substituted phenol isomers by ordinary stationary phases presents some difficulties, since these isomers have similar boiling points and polarities.A stationary phase able to separate on a basis other than boiling point or polarity is essential. Several studies have centred on liquid crystalline

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“…of liquid crystals as stationary phase in GC was first reported by Kelker in 1963. 30 · 31 This field has been extensively reviewed.…”

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confidence: 99%

Synthesis of High Temperature Mesomorphic Polysiloxanes and Their Use as Stationary Phases for High Resolution Gas Chromatography

Lin

Hsu

1993

Polym J

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ABSTRACT:Two new liquid crystalline polysiloxanes with very wide mesomorphic temperature range have been prepared. One containing 4-[(S)-2-methyl-l-butoxy]phenyl 4-hexanyloxybiphenyl-4'-carboxylate side groups displays enantiotropic smectic A, chiral smectic C and smectic B phases. The other containing (S)-2-methyl-l-butyl 6-(4-undecanyloxybiphenyl-4'-carbonyloxy)-2-naphthalenecarboxylate side groups exhibits only an enantiotropic cholesteric phase. Both mesomorphic polysiloxanes were used as stationary phases in gas chromatography capillary columns. They show very unique separating properties for various isomeric halogenated naphthalene compounds, methylanthracene compounds, fatty acid methyl esters and polycyclic aromatic compounds.KEY WORDS Liquid Crystalline Polymers / Mesomorphic Polysiloxanes / Gas Chromatography / Liquid Crystal Stationary Phases / Thermotropic side-chain liquid crystalline polysiloxanes were first synthesized by Finkelmann and Rehage. 1 Since then, nematic, smectic and cholesteric liquid crystalline polymers, and elastomeric liquid crystalline networks containing polysiloxane backbone 2 -11 have been synthesized. Some of the synthetic works summarized above has been already reviewed. 12 -15 Interest in the polysiloxane backbone for the preparation of side-chain liquid crystalline polymers (LCPs), comes from the low glass transition temperature and high thermostability exhibited by this class of polymers.Recently, high temperature mesomorphic polysiloxane "solvents" have demonstrated excellent potential as stationary phases in gas chromatography (GC) because of their superior properties with regard to chromatographic efficiency and thermal stability. 16 -29 The use * To whom all correspondences should be addressed.of liquid crystals as stationary phase in GC was first reported by Kelker in 1963. 30 · 31 This field has been extensively reviewed. 32 -34 Unlike conventional stationary phases that provide separation based on solute vapor pressure and/or different solubility arising from specific energetic interactions, liquid crystal stationary phase yield separation based upon differences in solute molecular shape. Although the properties exhibited by many monomeric liquid crystals are good from the point of view of GC requirements, polymeric liquid crystals are attracting growing attention because they offer significant improvements in column efficiency as well as thermal stability over monomeric liquid crystals.In this work, the synthesis of a new chiral smectic and a new cholesteric liquid crystalline polysiloxanes which can be used as GC stationary phase over a wide temperature 153

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Verhalten einer optisch anisotropen Schmelze als stationäre Phase in der Gas‐Flüssigkeits‐Verteilungschromatographie

Cited by 85 publications

References 4 publications

HPLC study of the intramolecular cyclization of a new nematogenic molecule. The gas chromatographic properties of the resulting liquid crystal

HPLC study of the intramolecular cyclization of a new nematogenic molecule. The gas chromatographic properties of the resulting liquid crystal

Synthesis and powder X-ray diffraction of new Schiff-base liquid crystal

Synthesis of High Temperature Mesomorphic Polysiloxanes and Their Use as Stationary Phases for High Resolution Gas Chromatography

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