Surface effects on liquid crystals of bent-shaped molecules

Recently we showed [1] that polymer network renders chirality to racemic SmCP structures of bent-shaped molecules. It was observed that the polymer network (chiral or non-chiral) favors a chiral state over the thermodynamically stable racemic state due to the inversion symmetry breaking at the polymer - liquid crystal interfaces. The chirality transfer can be locally suppressed by exposing the liquid crystal to a strong electric field treatment. Here we report detailed observations about the surface effects on a banana-shaped liquid crystal material 1,3-phenylenebis [3- fluoro-4-noctyloxy-phenyliminomethyl) benzoate] (PBFOB). The surface effects are controlled either by sandwiching the bent-shaped molecules in glass cells with different thickness and having different coatings on the glass substrates, furthermore by filling the material in cells containing various polymer network structures. The magnitude of electric polarization, conductivity and the switching dynamics of the material were investigated when filled in such cells. We observe that macroscopic chirality can also be induced partially when the material was filled in empty cells with thickness of about 1.5 mum or less. The surface anchoring properties have an important influence on the dynamics of the polarization switching, too. Our studies indicate that surfaces prefer anticlinic director structures.