Novel monomeric and polymeric liquid crystalline compounds were synthesized as stationary phases for gas chromatography (GC) and supercritical fluid chromatography (SFC). Monomeric liquid crystalline compounds were used in packed column gas chromatography for the separation of isomeric aromatic compounds and insect sex pheromones. Liquid crystalline polymers possess long nematic ranges and a uniform coating was easily achieved in glass and fused silica capillaries, which could stand temperatures up to 25OOC in GC and pressures of 200 MPa at 160OC in SFC. The columns provide excellent selectivity and resolution for fused ring aromatic compounds such as the isomers anthracene and phenanthrerie or triphenylene and chrysene.
New enantiotropic liquid crystalline compounds based on 4-@-substituted pheny1azo)phenol and m-cresol esters containing an acryloyloxy group were synthesized. Polyacrylates were prepared from these monomers by radical polymerization. The resulting polymers exhibit nematic enantioropic properties. The polyacrylates have broader nematic ranges and higher nematic to isotropic transition temperatures as compared to their corresponding monomers. The nematic range is dependent on both the lateral substituents and the terminal substituents. The laterally substituted polyacrylates gave a narrower nematic range than unsubstituted compounds.Increase in carbon number in the terminal alkyl group leads to a broader nematic range. The liquid crystalline polyacrylates could be coated uniformly on the inside of a glass capillary tubing. The coated capillary columns show an excellent selectivity in gas chromatography for the separation of isomeric compounds. The liquid crystalline stationary phases are highly stable up to 230 "C without column bleeding.
Liquid crystalline polyacrylates (LCPAs) are evaluated as stationary phases for capillary gas chromatography (CGC). Aromatic hydrocarbons as well as polar isomeric compounds are used as test solutes to compare the polarity of the LCPAs with a conventional polysiloxane column and a Carbowax 20M column. The relative polarityof thecolumns with respect tochange in the lateral and terminal substituents is also discussed. Lateral substitution, polarity of the terminal group, together with the solute size, affect the LCPA selectivity.
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