Synthesis of Schiff's base and azo liquid crystalline crown ethers

Six Schiff's base and azo liquid crystalline crown ethers were first synthesized via the intermediates cis(trans)-4,4′-diaminodibenzo-18-crown-6 and 4′-aminobenzo-15-crown-5, respectively. The structures were elucidated by elementary analysis, IR, 1H NMR and MS. The mesomorphic properties were determined by DSC and optical microscopy. The relationship between the structures of the double-armed and mono-armed crown ethers, and the mesomorphic properties were studied. We realized that when the L/D ratio of the doublearmed crown ether was in the range of 4-8 and that of the mono-armed crowns was larger than 3, they would possess liquid crystallinity. This conclusion is consistent with our previous investigations.