Surface nematic order induced by silane derivatives studied by second harmonic generation

We studied surface second-harmonic generation from thin layers of several silanes dipped on conductive glasses after the deposition of a thin film of 4'-n-pentyl-4-cyanobiphenyl (5CB) nematic liquid crystal. The average orientation and surface order of the nematic were determined by using Fourier analysis of the second harmonic signal obtained by sample rotation in reflection geometry and by polarization rotation in transmission geometry. The aim was to check the possible use of these materials as a control layer for the anchoring properties of nematics. The silane layer should passivate a conventional surface treatment mainly by changing the surface order properties