Smectic A phases with strings of interdigitated molecules in swallow tailed compounds

Abstract

X-ray diffraction studies are reported of smectic A phases exhibited by swallow-tailed compounds. The special molecular shape consisting of regions having differing space filling requirements results in antiparallel packing of the molecules; this influences the conformations of the alkyl chains. The layer spacings show unusually good agreement with the molecular lengths and this is the case for molecules with long and short aliphatic chains. We have observed also an additional incommensurable structural element which we believe to be unique for non-polar, low molar mass compounds. The X-ray diffraction patterns provide evidence for the existence of strings of interdigitated molecules.