Liquid-crystalline behaviour of molecules with tetrahedral symmetry

Abstract

It is shown that molecules with tetrahedral symmetry can give smectic liquid-crystalline phases, both with liquid and with ordered layers. In contrast to the usual behaviour the layering is rather strong, leading to three orders in the X-ray diffraction pattern. A tentative model is given in which the long mesogenic substituents are bent at the spacers with which they are attached to the central carbon atom, such that in spite of the tetrahedral angles a rod-like shape is obtained.