The binary system composed of a bent-core compound forming a B₇ phase and a nematogenic calamitic compound

Abstract

The isobaric phase diagram for a binary system of liquid crystals is presented. One mixing component is a bent-core mesogen forming a B₇ phase and the other one is a nematogenic calamitic compound. The occurring mesophases have been identified by their optical textures as well as by X-ray investigations. The B₇ phase exists down to about 60 mol% of the bent-core compound A / 40 mol% of the calamitic compound B. Two additional mesophases are induced in the mixed phase region. At medium concentrations (around 50 mol%) an oblique columnar phase appears which shows a similar X-ray pattern to the B₇ phase but an utterly different nucleation on cooling the isotropic liquid and a completely dissimilar texture. At concentrations below 35 mol% A, a further phase is induced which possesses an irregularly modulated layer structure. This phase can be regarded as an intermediate state between the regularly modulated Col_r (B₁) phase and the intercalated B₆ phase. It transforms on cooling into the phase with a regularly modulated structure.

Keywords:

• bent-core mesogen
• binary system
• B₇ phase
• calamitic mesogen
• columnar phases

Acknowledgements

The work was supported by DFG (Deutsche Forschungsgemeinschaft). S.H. thanks DAAD (Deutscher Akademischer Austauschdienst) for financial help.