Rigid-rod liquid crystalline polyesters based on n-alkoxyterephthalic acid and 4,4'-dihydroxybiphenyl

The synthesis and characterization of polymers obtained by polycondensation of n-alkoxyterephthalic acid (n = 1, 3, 5, 7) and 4,4'-dihydroxybiphenyl was carried out. The n-alkoxy groups promote processability of the polyesters by lowering the m.p. All polyesters show a nematic phase at about 300°, almost independently of the alkyl side chain length. Isotropization was not obsd. up to 450°, where thermal decompn. occurs. The glass transition temp. decreases with increasing n, ranging from 170° (n = 5) to 220° (n = 1)