New isothiocyanato liquid crystals containing thieno[3,2-b]thiophene central core

New isothiocyanato liquid crystal (LC) materials based on thieno3,2-b]thiophene core have been synthesised and characterised. Their mesomorphic and physical properties were evaluated. The results indicate that most of the new compounds exhibit only enantiotropic smectic A phases with high clearing points, and the difluorinated compounds (A3 and A6), in particular, also display a stable nematic phase with low melting points. Compared with the corresponding biphenyl and thiophene-phenyl analogues, these thieno3,2-b]thiophene-based compounds possess increased birefringence (the highest value found to be 0.40) and mesogenic phase intervals. These new thieno3,2-b]thiophene-based LCs exhibit a high birefringence and a high clearing point and are of potential use as components of high birefringence mixtures.