Flexoelectric studies on mixtures of compounds made of rodlike and bent-core molecules

We report measurements of the temperature variations of the flexoelastic ratio (e(1)-e(3))/K of octadecyl cyanobiphenyl and a mixture of this compound with another one with bent-core (BC) molecules, using hybrid aligned nematic cells. Addition of 5 mol % of the BC compound doubles the flexoelastic ratio, implying that the BC compound has similar to 20 times larger value compared to that of the compound with calamitic molecules. Mixtures with >11 mol % of the BC compound exhibit only a homeotropic alignment. We develop a simple model to account for this result which arises because of a large positive self-energy due to flexoelectric polarization.