Symmetry and defects in the CM phase of polymeric liquid crystals

Motivated by the recent discovery of a novel biaxial and orthogonal smectic polymeric liquid crystal with in-plane fluid order (smectic CM), we diecues defects allowed by ita symmetry. Smectic CM has not yet been found in low molecular weight liquid crystals. We point out that the observation of defecta provides a useful tool to distinguish smectic CM from other biaxial and fluid smectic phases known m smectics C and CZ. The structure of a possible ferroelectric, but nonchiral phase (smectic CP) is briefly discussed.