Synthesis and mesomorphic properties of some fluorinated phenyl 4-[(4-n-alkoxyphenyl)ethynyl]benzoates

Eight homologous series of fluorinated phenyl 4-[(4-n-alkoxyphenyl)ethynyl] benzoates have been synthesized. Textural observations by polarizing micros copy and DSC measurements of the phase transitions show that most of these compounds are thermotropic liquid crystals with nematic and smectic A phase s; furthermore, several show monotropic high order smectic phases. The resu lts showed that the SmA phase is enhanced with increasing degree of fluoro- substitution on the para- and meta-positions of the terminal phenyl groups. The mesomorphic properties of these compounds are also affected by the dir ection of ester bonds. The effect of triple bonds is also discussed.