Synthesis And Inducing Blue Phase Liquid Crystals Of 1,3,4-Oxadiazole Bent-shaped Molecules

A series of bent-shaped molecules based on 1,3,4-oxadiazole core with different terminal chain length and conjugated chain were synthesized. The chemical structures are confirmed by 1H nuclear magnetic resonance (1H NMR) and high-resolution mass spectrometry (HRMS). Their phase transition behaviours were analysed by polarised optical microscopy (POM) and a differential thermal analyzer (DTA) Then the compounds were doped into N*LC host which is composed of nematic liquid crystal and chiral materials to induce the blue phase. The effects of their terminal chain length and conjugate chain on the blue phase were compared and analysed. The results showed that the blue phase can be induced only when the miscibilities between the bent-shaped molecules and N*LC host are good. In addition, it is also found that the mechanism of a blue phase induced by bent-shaped molecules is mainly related with its geometry, no matter wether a liquid crystalline phase exsits or not. In other words, the molecular biaxiality plays an important role in the blue phase range, and the larger bent angle is evident of its biaxiality and the greater stability of the induced blue phase.