Structure of the 'Dark Conglomerate' Phase of Bow-Shaped Liquid Crystals

The recent interest in bow-shaped molecules has revealed a startling variety of new phases. The bent cores of these molecules have a strong tendency toward polar ordering in smectic layers. Most bow-shaped materials also exhibit molecular tilt around the polar axis leading to spontaneous chiral symmetry breaking. Despite an achiral molecular structure, this chirality appears strong enough in some materials to disrupt the long range order of the smectic layers in the so-called 'Dark Conglomerate' phase. We report on the use of polarized light microscopy, freeze fracture microscopy, and x-ray scattering in the determination of the structure of this novel phase. This work supported by NSF MRSEC Grant DMR-0213918 and NSF Grant DMR-9803098