Homeotropic-planar anchoring transition induced by trans-cis isomerization in ultrathin polyimide Langmuir-Blodgett films

The influence of the charge separation during the trans-cis conformational change between the surface azobenzene 6Az5PVA monolayer on polyimide Langmuir-Blodgett film on the surface charge density is investigated, using the Maxwell displacement current technique. It is theoretically shown, in the framework of the molecular model, which takes into account interactions between the surface polarization (in the quadrupole approximation) and surface electric field, that the experimentally observed changes of the surface charge density in similar to3 x 10(-4) C/m(2), caused by the charge separation in similar to2 pC, taking place during the conformational change, may lead to changing of the surface alignment of liquid crystalline molecules, such as 4-n-pentyl-4'-cyanobiphenyl (5CB), having contact with that solid substrate. (C) 2003 American Institute of Physics.