Polycatenar bows with single carbon atom elbow

Abstract

A new family of six aromatic ring-containing bent-shaped mesogens in which the central elbow is a ketone, a secondary alcohol or a methylene group (6: CO, 7: CHOH, 8: CH₂) is described. The effects of the variant elbow as well as the number of terminal alkoxy chains on the mesomorphic properties have been studied. The results showed that, except for two compounds deprived of mesomorphism, all the other bent derivatives were found to exhibit mesophases. All the dicatenar compounds are mesomorphic, and depending on whether the central joint is planar or tetrahedral, they display either a SmC phase or a B₁/B_1rev phase, respectively. Mesomorphism is suppressed in the two tetracatenars with a tetrahedral elbow while all the other polycatenars show a columnar phase with a 2D hexagonal symmetry. The investigation revealed that not only did the flexibility of the elbow and the number of terminal chains have a strong impact on mesogenic behaviour but the proper combination of these structural factors can lead towards axially polar columnar phases.