Odd–even effect in biphenyl‐based symmetrical dimers with methylene spacer – evidence of the B4 phase

Abstract

A series of 4‐decyloxy‐4′‐hydroxybiphenyl esters of α,ω‐alkanedicarboxylic acids containing two mesogenic units connected by a methylene spacer was synthesized. The mesogenic properties of the compounds were investigated by polarising optical microscopy, differential scanning calorimetry and X‐ray diffraction methods. A strong influence of the spacer length and its parity on the mesomorphic properties was found. A dramatic odd–even effect was observed for the clearing temperatures and entropies. Compounds with an even number of carbon atoms in the methylene spacer formed tilted smectic phases, whereas compounds with an odd number of carbon atoms in the spacer exhibited the B4 phase, characteristic of bent‐shaped molecules.

Keywords:

• symmetric dimer
• smectic phase
• bent‐shaped molecule
• B4 phase

Acknowledgement

This work was supported by grant ESF/213/2007.