Liquid command surfaces

Figure 4.39. Controlling the orientation of a liquid-crystalline phase using a command surface...

K. Ichimura, Y. Suzuki, T. Seki, A. Hosoki, K. Aoki, Reversible Change in Alignment Mode of Nematic Liquid Crystals Regulated Photochemically by Command Surfaces Modified with Azobenzene Monolayer , Langmuir, 4, 1214 (1988)... 

The corresponding fatty acid could not be photoisomerized in the LBK film. By attaching the azobenzene chromophore to the hydrophilic backbone, however, the free volume in LBK films was increased and photoisomerization was possible (i.e., 50 to 70% cts-isomer compared to 0% for the nontethered azobenzene amphiphile and 90% cis-isomer in solution). However, concomitant with the increased free volume, there is a decrease in the orientational order of the chromophores. These polymers have been widely used as command surfaces to control the orientation of liquid crystals and to investigate the photomechanical effect. ... 

K. Ichimura, K. Photoalignment of Liquid-Crystal Systems. Chem. Rev. 100, 1847 (2000). Ichimura, K., Seki, T, Kawanishi, Y., Suzuki, Y., Sakuragi, M., and Tamaki, T. Photocontrol of Liquid Crystal Alignment by Command Surfaces , in Photoreactive Materials for Ultrahigh Density Optical Memory. M. Irie, Ed., Elsevier Amsterdam, (1994), p. 55. 

Ichimura, K., Suzuki, Y., Seki, T., Hosoki, A., and Aoki, K. Reversible change in alignment mode of nematic liquid crystals regulated photochemically by command surfaces modified with an azobenzene monolayer. Langmuir, 4, 1422 (1988). 

Ubukata, T., Seki, T, and Ichimura, K. Modeling the interface region of command surface. Parr 1. Structural evaluations of azobenzene/liquid crystal hybrid Langmuir monolayers. /. 

K. Ichimura, H. Akiyama, N. Ishizuki, and Y. Kawanishi, Command surfaces. 6. Azimuthal orientation of liquid crystals photocontrolled by an azobenzene pendent polymer, Macromol. Chem., Rapid Commun. 14, 813-917 (1993). 

S. Yamamura, T. Tamaki, T. Seki, M. Sakuragi, Y. Kawanishi, and K. Ichimura, Reversible alignment change of liquid crystals induced by photochromic molecular films. Part 18. a-Hydrazono-p-keto esters as command surface, Liq. Cryst. 13, 189-199 (1993). 

K. Ichimura, H. Akiyama, K. Kudo, N. Ishizuki, and S. Yamamura, Command surfaces 12. Factors affecting in-plane photoregulation of liquid crystal alignment by surface azobenzenes on a silica substrate, Liq. Cryst. 20, 423 435 (1996). 

K. Ichimura, K. Kudo, and H. Tomita, Command surfaces 14. Photoregulation of in-plane alignment of a liquid crystal by the photoisomerization of stilbenes chemisorbed on a substrate surface, Liq. Cryst. 20, 161-169 (1996). 

Seki T, et al. 1993. Command surfaces of Langmuir Blodgett films. Photoregulations of liquid crystal alignment by molecularly tailored surface azobenzene layers. Langmuir 9(1) 211 218. 

Ichimura K, Seki T, Kawanishi Y, Suzuki Y, Sauragi M, Tamaki T. 1994. Photocontrols of liquid crystal alignment by command surfaces. In Irie M, editor. Photo reactive Materials for Ultrahigh Density Optical Memories. Amsterdam Elsevier. 

Seki et al. (1993) developed a command surface concept, which uses the azobenzene derivatives bound on the Langmuir-Blodgett (LB) films to control the orientation of the liquid crystal molecules on the film surfaces by the photoswitching of the azobenzene moieties. Maeda et al. (2006) extended this concept to control the adsorption properties of mesoporous silica materials by reversible photoswitching of the azobenzene moieties anchored on the pore surfaces. 

The photoalignment process is particularly useful at the mesoscopic level in the context of liquid crystals, the alignment of which can be controlled with azobenzene command surfaces [24, 25]. Alternatively, a small portion of master azobenzene molecules can be doped into a liquid crystal material where they control the orientation of passive slave molecules through collaborative movements. In an extreme case, the azobenzene dopants can induce order-disorder transitions of the hquid crystal material, as illustrated in Fig. Ic [20]. 

H. Knobloch, H. Orendi, M. Buchel, T. Seki, Sh. Ito, and W. Knoll, Command surface controlled liquid crystalhne waveguide structures as optical information storage. Journal of Applied Physics 76, 8212 (1994). 

---