Gas chromatographic properties of some liquid crystals containing dioxyethylene ether terminal chains

Comparative gas chromatographic properties of four rod-like liquid crystals coated on capillary columns are studied. These four liquid crystals contai n the same number of atoms in their backbones. They differ by the partial o r total replacement of the two terminal heptyloxy chains by a 2-(2-methoxye thoxy)ethoxy (called also dioxyethylene ether) chain. Synthesis and thermal properties of these four liquid crystals are presented. It appears that th e introduction of dioxyethylene ether decreases the two transition temperat ures as well as the nematic range. With regards to the chromatographic sepa ration abilities, the four liquid crystals are efficient before and after s olid-nematic or nematic-liquid transitions; however, the plate numbers are higher in the nematic state. Interesting analytical applications are demons trated in different fields : isomeric separation of alkanes, aromatics, pol yaromatics, volatile aroma compounds, cis and trans isomers and phenols. Th e increase of the number of oxyethylene units permits to drastically increa se the separation efficiency for polar solutes.