Orientation of liquid crystal molecules on command surface LB monolayer studied by the surface potential and SHG technique

Orientation of the liquid crystalline (LC) and command surface molecules was investigated by the surface potential and optical second-harmonic generation (SHG) measurement. LC ultra thin film was prepared on azobenzene command surface (6AZ10-PVA) LB monolayer by the evaporation. SHG measurements show that LC molecules are deposited on 6AZ10-PVA monolayer so as to compensate the hyper-polarizability of azo side chain. Surface potential measurements indicate that dipole moment of the azo side chain and LC molecule faces toward each other. Orientational change of the LC molecules due to the photoisomerization of 6AZ10-PVA surface was also observed by the SHG measurement. Oriented gas model demonstrates that tilt angle of the LC molecules increases with the photoirradiation.