Mesogenic aromatic esters with sulphur containing alkyl chains

A new series of aromatic esters, 1 and 2 with a sulphur atom in one of the side chains, is described. They exhibit nematic and/or smectic A/C mesophases as a function of the length of the alkyloxy chain. The presence of sulphur in the 4-position of the alkanoyloxy chain depresses both the clearing and the melting points with respect to the corresponding carbon analogues 3, resulting from the higher conformational mobility of the thiaalkyl chain. In 2, the presence of a methyl group in the 2-position of the alkanoyloxy chain induces a S_A phase below room temperature.