PROPERTIES OF THE LIQUID-CRYSTALS FORMED BY CERTAIN 4'-N-ALKYLBIPHENYL-4-YL 5-N-ALKYLTHIOPHENE-2-CARBOXYLATES

Thirty compounds, ten members of each of three homologous series of es ters derived from 4-hydroxy-4'-n-octyl-, -nonyl-, and -decyl-biphenyl and the 5-n-alkylthiophene-2-carboxylic acids (methyl through to decyl homologues) have been prepared. The liquid crystal properties of thes e esters, which show extensive smectic polymorphism, have been investi gated by thermal optical microscopy, differential scanning calorimetry , and miscibility studies. Four members of the corresponding 4-n-alkyl benzoates have also been prepared in order to compare their liquid cry stal behaviour with the 5-n-alkylthiophene-2-carboxylate counterparts: both smectic and nematic thermal stability are higher for the 4-n-alk ylbenzoates, by 30.6 degrees and 36.8 degrees C, respectively.