FLUOROSUBSTITUTED CHIRAL LIQUID-CRYSTALS DERIVED FROM (R)-2-(4-HYDROXYPHENOXY)PROPAN-1-OL

Two homologous series of (R)-2-(4-hydroxyphenoxy)propan-1-ol derived materials were synthesized; the (R)-1-alkoxy-2-[4-(2'-fluoro-4'-pentylbiphenyl-4-ylcarbonyloxy)phenoxy]propanes and the (R)-1-alkoxy-2-[4-(2,3-difluoro-4'-pentylbiphenyl-4-ylcarbonyloxy)phenoxy]propanes with alkoxy groups from methoxy to hexyloxy. These materials all showed thermotropic liquid-crystalline properties which illustrate the influence of the fluoro substituents, in giving reduced melting points, clearing points, and smectic A to chiral nematic transitions, relative to their non-fluoro-substituted parent system. Certain members of both series, especially the higher homologues, showed chiral nematic phases at, or around, room temperature. The transition temperatures for both series are discussed in terms of the influence of the fluoro substituent in relation to its position within the aromatic core.