Bistable linear electro-optical switching in the B₇' phase of novel bent-core molecules

Three novel symmetrical bent-core compounds were synthesized where the terminal alkoxy linkages of the original bent-core mesogen forming a B phase was converted to -alkyl carboxylates. It is found that instead of the B phase, all three compounds exhibit a transition between B' and B mesophases. The physical and electro-optical properties have been investigated by polarizing optical microscopy, differential scanning calorimetry, X-ray diffraction and electric field experiments. The higher temperature B' phase has been shown to exhibit bistable but analogous linear electro-optical switching without any observable polarization peak. We analyze two theoretical models and find that a local triclinic symmetry may be responsible for the unusual electro-optical switching.