Structure and photoconductive behaviour of a sanidic liquid crystal

A series of [1]benzothieno [3,2-b][1] benzothiophene-2,7-dicarboxylate deri vatives consisting of a flat, conjugated aromatic moiety containing sulphur hetero-atoms and substituted by terminal chains-ethyl, decyl, Z-4-decenyl or 2-(2-butoxyethoxy)ethyl-has been synthesized. These materials exhibit a smectic liquid crystalline phase, the stability of which was found to be st rongly dependent on the length and the nature of the terminal chains. In th e mesophase, the molecular arrangement within the smectic layer is characte rized by a local stacking of the rigid parts similar to that found in disco tic columnar systems. Finally, clear photoconductive behaviour was found in mechanically aligned samples of these liquid crystals.