Preparation and structural properties of an azobenzene liquid crystal Langmuir-Blodgett film

Azobenzene-containing liquid crystal, 2-hydroxy-4-hexyloxy-4'-hexyloxy azob enzene (AB), was synthesized and used to produce LB films. The surface pres sure cs surface area isotherm showed that the liquid crystal molecules form ed a stable multilayer on the water subphase owing to the self-assembly for their much smaller area per molecule with 0.1 nm(2) at pi = 0 and 0.07 nm( 2) at collapse point. This spontaneous behavior was also confirmed by small angle X-ray diffraction for a 'horizontally once-transferred' LB film. The 'vertically multi-transferred' LB film also exhibited the same ordered lay er structure with the long spacing of the multilayer about 2.0 nm. Polarize d FTIR spectra were used to measure the orientation of liquid crystal molec ules in LB films with a tilt angle of 60 degrees and 48 degrees (correspond ing to azobenzene moiety and hydrocarbon chain, respectively), which is wel l in accordance with the result of X-ray diffraction.. The result from UV-v is absorption spectra revealed that the AB molecule formed H-aggregation in LB films. (C) 1998 Elsevier Science Limited. All rights reserved.