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

The thermotropic liquid-crystalline behaviour of a number of (R)- and (R,S)-2-(4-substituted-phenoxy)-1-alkoxy propanes has been examined an d related to changes in the nature of the mesogenic core and the termi nal alkoxy substituent. Compounds containing a 4'-pentylbiphenyl-4-car bonyloxy core were generally found to display smectic A and the more o rdered crystal B mesophases; in contrast the 4-(4-trans-pentylcyclohex yl)benzoyloxy-derived series showed chiral nematic and Blue phases in addition to the smectic A and crystal B phases. Furthermore, the high optical purity of these materials was demonstrated by use of H-1 NMR a nd chiral shift reagent techniques, and confirms the stability of the chiral centre towards racemization.