High-temperature nematic liquid crystal for gas liquid chromatography

Abstract

The synthesis of three liquid crystals with the general formula N, N'-bis( p a l koxyp henylbenz ylidene )-a,a'-bi-p-toluidine where the alkoxy group is represented by methoxy (BABT; nematic range of 253-370 " C ) , n-butoxy (BBPT; nematic range of 232-331 O C ) , and benzyloxy (BBzPT; nematic range 270-346 " C ) is reported. The liquid crystals were synthesized by the condensation of the appropriate 4'-alkoxybiphenyl-4-carboxaldehyde with a,a'-bi-p-toluidine. The aldehydes were prepared by a five-step procedure starting with Mydroxybiphenyl. BABT was chromatographically evaluated. BABT operating in the supercooled nematic region at 230 O C provided better separations of methyibenzanthracene Isomers than conventional SE-30, Dexsii 300, and Silicon Gum MS2211 columns.The development of high-temperature liquid crystals for use as stationary phases in gas-liquid chromatography (GLC)is rapidly gaining appreciation. The topic was recently reviewed by Kelker ( I ) and Janini ( 2 ) . Several recent applications of liquid crystal phases have been reported (3-11). Our

Synthesis of a new liquid crystal, 4-[(4-chlorobenzyl)oxy]-4′-cyanoazobenzene and its use as stationary phase in gas-chromatography

“…Difficult separations of geometric isomers of 3-5 ring polyaromatic hydrocarbons and of m-, p-, o-isomers were carried out on liquid crystals as stationary phases in the nematic [1, 2, 4-7, 11, 12], supercooled nematic [10,13,14], smectic and nematic ranges [1] or in solid state [9,15]. According to most of the publications, the separation took place in the nematic region.…”