Pyramidic Mesophases

Abstract

Two series of mesogenic compounds consisting of a rigid pyramidal central core and six equal flexible side chains were synthesized and their mesomorphic properties studied by calorimetry and optical microscopy. The two series of compounds are: I-hexaalkyloxytribenzocyclononene and II-hexaalkanoyloxytribenzocyclononene. In series I, enantiotropic mesophases appear for homologues in which the number, n, of carbon atoms in each side chain is equal or larger than six, while for series II mesomorphism is exhibited for all the compounds studied (8- 15). Some of these exhibit dimorphism (i.e. I-11 and II-12 to II-14) and even trimorphism (II-11). In total Five different mesophases are identified in both series. Several of these are stable at room temperature. Optical measurements indicate that they are not layered, they appear to be columnar. Due to the pyramidal shape of the central core of the constituent molecules special molecular arrangements for these mesophases are possible. It is suggested to call them pyramidic mesophases.