SYNTHESIS, THERMODYNAMIC PROPERTIES, AND GAS-LIQUID-CHROMATOGRAPHIC EVALUATION OF A HIGH-MELTING LIQUID-CRYSTAL SERIES

The synthesis, phase transition temperatures and thermodynamic data (enthalpies and entropies) are reported for the methoxy through n-octyloxy (and n-decyloxy) homoloques of the liquid crystal series represented by N,N prime -bis left bracket p-alkoxybenzylidene right bracket - alpha , alpha prime -bi-p-toluidine. The trends in transition temperatures are more or less analogous to previously-studied liquid crystal series. Nematic-isotropic enthalpy values are appreciably higher than average values for other series. Entropy values show the usual odd-even effect, but in contrast to observed trend for other series, they decrease with increasing terminal substituent chain length. Di-Schiff's bases with various terminal substituents that showed interesting linear correlation between nematic-isotropic transition temperatures and the anisotropy of polarizability of the substituent were also synthesized. A simple gas-liquid chromatographic method for the investigation of the selectivity of nematic stationary phases and its dependence on the degree of molecular order in the nematic state is also presented.