The 2D-correlated structures of a lyotropic liquid crystalline diol with a phenylpyrimidine core

Abstract

Even though the fluid tilted smectic C (SmC) phase is one of the most common phases in thermotropic liquid crystals, the lyotropic analogue to SmC is practically unknown so far. One of the rare examples, a lyotropic liquid crystalline diol, which was reported in 1991 to show this phase, was re-examined by means of detailed X-ray diffraction and polarised optical microscopy. Although the diol possesses a smectic C promoting phenylpyrimidine core, it was not possible to verify the existence of a SmC-analogue lyotropic phase. Instead, the phase diagram shows the existence of five different lyotropic phases identified as nematic, lamellar L_α and hexagonal as well as two novel complex 2D-correlated lyophases. Results obtained by electron density calculations and X-ray diffraction data strongly suggest that the structure of one of these phases possesses a pseudo-c2mm symmetry and is built up of two different kinds of columns, whereas the other one is a ribbon phase of the oblique plane group p2.