Flexoelectric liquid crystal bimesogens

Recently we have shown that short pitch chiral nematogenic bimesogens may be synthesized that couple weakly via the bulk dielectric anisotropy but extremely strongly via the flexoelectric effect to give exceptional flexoelectric, room temperature, fast electro-optic switching characteristics. Typical switching times are 100 mus with bipolar switching angles of 90degrees at fields of 5V mum(-1). In the present work we show how changes to the molecular structure, namely replacing the ether linkages with ester groups, control the bulk flexoelectric switching properties of these bimesogenic nematic materials. Due to the strong monotropicity of the ester bimesogens, mixtures with the more enantiotropic ether linked bimesogens were made, and the effect on the flexoelectric coefficient behaviour investigated.