P-CYANOAZOBENZENE AS A COMMAND MOLECULE FOR AZIMUTHAL ANISOTROPY REGULATION OF A NEMATIC LIQUID-CRYSTAL UPON EXPOSURE TO LINEARLY POLARIZED VISIBLE-LIGHT

UV exposure of a nematic liquid crystalline cell fabricated with a quartz plate surface-modified with p-cyanoazobenzene units resulted in no reversible alignment change. On the contrary, irradiation with linearly polarized visible light (>430 nm) brought about in-plane anisotropy of the mesophase although the photostationary state under the visible light illumination consisted predominantly of the trans isomer with no apparent geometrical photoisomerization. The direction of the photoinduced azimuthal anisotropy was approximately perpendicular to the polarization plane of the actinic light and controllable by changing the polarization plane. This technique was applicable to form photoimages on the basis of the difference in the direction of anisotropy. The photoinduced birefringence of the cell was stable at room temperature even upon exposure to light unless the light was not polarized.