Chiral liquid crystal polymers. VIII Thermotropic poly(ester-β-sulphide)s based on variously spaced twin p-oxybenzoate diads

The synthesis and characterization both in solution (chiroptical properties) and in bulk (thermotropic properties) of a new series of structurally defined chiral liquid-crystalline poly(ester-β-sulphide)s are described. The functional polyesters are constituted by repeating units consisting of two p-oxybenzoate diads interconnected by a linear segment of m methylene groups (m = 6-10, 12), and strictly sequenced by the chiral (R)-3-methyl-1,6-hexanedithiyl spacer. The thermotropic behaviour deviates from the regular profiles generally established in homologous series of mesomorphic polymers and results in peculiar alternations of the liquid-crystalline properties, enantiotropism being exhibited by only a few, mainly odd-numbered, homologues of the series.