MESOMORPHIC PHASE-TRANSITIONS OF 4,4'''-DIALKYLOXYQUATERPHENYLS AND DIALKYL QUATERPHENYL-4,4'''-DICARBOXYLATES

The mesogenicities of 4,4'''-dialkyloxyquaterphenyls (DAQP) and dialky l quaterphenyl-4,4'''-dicarboxylates (DCQP) were studied by differenti al scanning calorimetry, optical microscopy and miscibility tests. The DAQP homologues, for which the number of carbon atoms in the alkyloxy group (n) is 1-9, showed a S-A phase, and the higher homologues (n=9- 18) showed a S-C phase. The propyl, butyl and pentyl esters of DCQP sh owed a S-A phase, and the octyl and dodecyl esters showed S-A and S-C phases. The isopropyl, isobutyl, 2-ethylhexyl and cyclohexyl esters sh owed a S-C phase and the branching of the alkyl group strikingly lower ed the mesophase thermal stabilities.