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 synthesize d by using palladium-catalysed cross-coupling procedures involving ary lboronic acids and alkynylzinc reagents with aryl iodides, bromides an d trifluoromethanesulphonates (triflates). The compounds have very hig h nematic phase stability, but their melting points are also quite hig h. The birefringences were measured using an extrapolation technique a nd the values were found to be between 0.26 and 0.42.