New tgba series exhibiting a SC*SASA*N* phase sequence

Abstract

A new series with a chiral tolane core has been synthesized. These materials belong to the optically active series: 3-fluoro-4-[(R) or (S)-1-methylheptyloxy]4′-(4″-alkyloxy-3″-fluorobenzoyloxy)tolanes (nFBTFO1M7). For the first time, the helical SA* phase or TGBA phase is found in all of the derivatives from heptyloxy to octadecyloxy. The SA-SA*-N* phase sequence is observed in several compounds with short chains and the SC*-SA-SA*-N* phase sequence is obtained with the decyloxy derivative. The TGBA phase has filament or cholesteric textures. The helical pitch of the TGBA phase is short for the octadecyloxy derivative and is compared with that for different chain lengths as a function of temperature. The layer spacing in the TGBA phase shows that it is incommensurate with the fully elongated molecular length. © 1992 Taylor & Francis Group, LLC.