THE SYNTHESIS AND HIGH OPTICAL BIREFRINGENCE OF NEMATOGENS INCORPORATING 2,6-DISUBSTITUTED NAPHTHALENES AND TERMINAL CYANO-SUBSTITUENTS

A range of nematogenic materials which incorporate a 2,6-disubstituted naphthyl moiety and a terminal cyano-substituent have been synthesized by using palladium-catalysed cross-coupling procedures involving arylboronic acids and alkynylzinc reagents with aryl iodides, bromides and trifluoromethanesulphonates (triflates). The compounds have very high nematic phase stability, but their melting points are also quite high. The birefringences were measured using an extrapolation technique and the values were found to be between 0.26 and 0.42.