The macroscopic motion of liquids on a flat solid surface was manipulated reversibly by photoirradiation of a photoisomerizable monolayer covering the surface. When a liquid droplet several millimeters in diameter was placed on a substrate surface modified with a calix[4]resorcinarene derivative having photochromic azobenzene units, asymmetrical photoirradiation caused a gradient in surface free energy due to the photoisomerization of surface azobenzenes, leading to the directional motion of the droplet. The direction and velocity of the motion were tunable by varying the direction and steepness of the gradient in light intensity. The light-driven motion of a fluid substance in a surface-modified glass tube suggests potential applicability to microscale chemical process systems.

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Quartz plates were treated with an azobenzene compound having a triethoxysilyl group to modify the surface with the photosensitive unit and were employed for constructing a nematic liquid crystalline cell.The reversible change in the transmittance of the cell set between two crossed polarizers was induced by alternate exposure to UV and visible light, which resulted in the photoisomerization of the monolayered azobenzene.

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Photoinduced orientational behavior of polymethacrylates with side chains (amorphous polymers, pMAz2 and C2MeO, and liquid crystalline polymers, C6MeO and C12MeO) with different alkylene spacer lengths (n ) 2, 6, 12) were investigated by means of polarized Fourier transform infrared (FT-IR) and UV-vis absorption spectroscopy. Being different from pMAz2, C2MeO showed high optical anisotropy due to in-plane orientation and the excellent thermostability even above T g, which can be explained in terms of potential liquid crystallinity to be able to have a tendency to form a well-ordered domain. We observed marked dependence of photoorientation processes on film temperatures of C6MeO. While in-plane orientation was generated in glassy state as well as at 76 °C, irradiation at 90 °C slightly lower than T SN (transition temperature between smectic and nematic phases) gave rise to the distinct transformation from in-plane orientation at the early stage to successive out-of-plane reorientation, which was accompanied by H-aggregation. This situation enabled ones to record optical images in a C6MeO film on the basis of the difference in birefringences between two orientational modes. The biaxial reorientation occurred also for C12MeO, though both in-plane and out-of-plane photoorientation occurred simultaneously at room temperature as well as elevated film temperatures.