For the first time, a series of polythiiranes bearing in the side chain biphenyl and 4-alkoxybiphenyl mesogenic groups connected to the backbone with spacer groups of different lengths were prepared by anionic ring-opening polymerization of the corresponding thiirane derivatives. Unlike the corresponding polyoxiranes described in the literature, large methylene or oxyethylene spacers were needed in polythiiranes to observe liquid crystalline properties. But like the polyoxiranes, the polythiiranes exhibited mainly high ordered smectic A and E mesophases which were characterized by the usual techniques : d.s.c., polarized optical microscopy and X-ray diffraction.