Helical smectic a* phase (tgba phase) in some tolan series

: A helical smectic A* phase between the isotropic liquid and the ferroelectric smectic C* phase is found in three new series with very long alkoxy chains. The materials belong to the optically active series : (R) and (S) 1-methylheptyl 4’-(4“-alkoxybenzoyloxy)tolan-4-carboxylates, 4’-(4“-alkoxy-3”-fluorobenzoyloxy)tolan-4-carboxylates, 4’-(4“-alkoxy-2”, 3“-difluorobenzoyloxy)tolan-4-carboxylates. This new phase has two typical textures: filament texture when the helix pitch is large and cholesteric texture (Grandjean texture) with a short pitch. © 1991, Taylor & Francis Group, LLC. All rights reserved.