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from the switching unit to a working unit that changes its function,
Matsumoto et al, have proposed a sensor with a photochromic azobenzene
dye as the switching unit. A photon received by the switching unit caused the
azobenzene moiety to isomerize. The signal produced by this molecular
deformation reached the working unit, a pyridinium (TCNQ} 2 complex,
121
which changed the electrical conductivity of the film (see Figure 6.27). 123

SUMMARY

LBK films are highly ordered and densely packed supramolecular assemblies.
The packing of the chromophores in LBK films influences their photo-
reaction. Therefore, LBK films have to be tailored by the choice of the
amphiphilic molecules and the transfer conditions to provide a matrix for the
chromophores that has sufficient flexibility and free volume for the photo-
reaction to occur. On the other hand, the LBK film's structure can be tailored
in such a way that the photoreaction of the chromophore enhances the struc-
ture or the properties of the entire film. In this way, photoactive films can be
designed to show a much more sophisticated photoresponse than that of a
chromophore in an inert matrix.

1. Spooner, S. P., and Whitten, D. G. Photoreactions in Monolayer Films and Langmuir-
Blodgett-Assemblies. In: Photochemistry in organized and constrained media, V,
Ramanmurthy, Ed. VCH: Weinheim (1991), p. 691.
2. Russel, J. C., Costa, S. B., Seiders, R. P. and Whitten, D. G. Photochemistry of Surfactant
Stilbene in Organized Media: A Probe for Hydrophobic Sites in Micelles, Vesicles and
other Assemblies./. Am. Chern. Soc. 102, 5678 (1980).
3. Quina, F. H., and Whitten, D. G. Photochemical Reactions in Organized Monolayer
Assemblies. 4. Photodimerization, Photoisomerization, and Excimer Formation with
Surfactant Olefins and Dienes in Monolayer Assemblies, Crystals, and Micelles. /. Am.
Chem.Soc.99, 877(1977).
4. Rennert, J. Photodimer Formation in the Condensed Phase of trans-Cmnamic Acid,
Photogr. Set. Eng. 15, 60 (1971).
5. Stobbe, H. Ber. Dtsch. Chem. Ges. 52, 666 (1919).
6. Mathauer, K., Schmidt, A., Knoll, W, and Wegner, G. Synthesis and Langmuir-Blodgett
Multilayer-Forming Properties of Photo-Crosslinkable Polyglutamate Derivatives.
Macromalecuks 28,1214 (1995).
7. Seufert, M,, Fakirov, C., and Wegner, G. Ultrathin Membranes of Moleculary Reinforced
Liquids on Porous Substrates. Adv. Mater. 7, 52 (1995).
8. Wiegand, G., Jaworek, T., Wegner, G., and Sackmann, E. Heterogeneous Surfaces of
Structured Hairy-Rod Polymer Film: Preparation and Methods of Functionalization.
Langmuir 13, 3563 (1997).
9. Kawamura, S., Tsutui, T., Saito, S., Murao, Y., and Kinae, K. Photochromism of
Salicylidenenanilines Incorporated in a Langmuir-Blodgett Multilayer. /. Am. Chem. Soc.
110, 509 (1988).
10. Brown, G. H. Ed. Photochroism, Wiley Interscience, New York (1971).
11. Polymeropoulos, E. E., and Mobius, D. Photochromism in Monolayers. Ber. Bunsenges.
Pbys. Chem. 83, 1215 (1979).
12. Hibino, J., Hashida, T., and Suzuki, M. Multiple Memory Using Aggregated Photochromic
Compounds. In Photoreactive Materials for Ultrahigh Density Optical Memory, M. Irie,