Mesogenic polymers. III. Thermal properties and synthesis of three homologous series of thermotropic liquid crystalline “backbone” polyesters

Abstract Details of the thermal behavior, including transition temperatures, transition heats and transition entropies, are reported for three series of nematic liquid‐crystalline “backbone” polyesters having the general structure magnified image All polysters described above were examined by differential scanning calorimetry and were found to have reproducible thermal behavior once the polymer had been annealed by heating to the isotropic phase and then subsequently cooled. Enantiotropic nematic phases were found for all 30 polysters studied. Many polymers showed multiple endotherms on melting to the nematic phase. Plots of solid–nematic and nematic–isotropic transition temperatures versus number of carbon atoms in the diacid segment ( x ) for each ( y ) reveal an even–odd alternation reminiscent of trends in homologous series of small‐molecule liquid crystals. Enthalpies for the solid → nematic and nematic → isotropic transitions do not show such a precise alternation.