Generation of Maxwell-displacement-current and photoregulation of liquid crystal alignment using azobenzene monolayers

The Maxwell-displacement-current (MDC) measuring technique has been applied for the investigation of monolayers of poly(vinyl alcohol)s bearing azobenzene side-chains (6Az5PVA) for reversible photoisomerization on liquid crystal (LC) cells. The MDC generated by photoisomerization of surface azobenzene monolayers includes two parts, one due to the change of the capacitance of the LC cells and the other due to the change of the polarized charge in the surface azobenzene layer. The alignment of nematic LC (5CB) with positive dielectric anisotropy and a nematic (DON-103) with negative dielectric anisotropy is studied, by applying cis-form 6Az5PVA monolayers. During irradiation by UV and visible light, eight peaks (5CB) and four peaks (DON-103) appeared in the transmission intensity, respectively, possibly because the azobenzene alignment layers change trans- and cis-form and LCs rotated for π/2 radian. We conclude that 6Az5PVA monolayers deposited in the cis-form can photoregulate the alignment of LCs