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SynopsisPolypyrrole-PMMA compoaite films have been prepared with the chemical oxidative polymerization by spreading the water-insoluble solvent solution of pyrrole and PMMA mixture on the surface of the aqueous solution containing K.&O,, the oxidizing agent. The conductivity of the films increases rapidly, passes through a plateau, and then decreases gradually as the reaction time increases. The conductivity of the oxidized side of the f i l m is higher by over 1 order of magnitude than that of the evaporated side. It is due to the fact that the former is rich in polypyrrole while the latter is rich in PMMA. The thickness of the films can be controlled by adjusting the PMMA concentration. However, the lower limit of the f i l m thickness is practically in submicron order. The relationship between the transmittance and the logarithm of the conductivity of the films gives a straight line with a gradient, ca. -8. The conductivity of the films is stable on silicagels in a desiccator over 2000 h at 25°C. The conductivity of the f i l m is, however, very sensitive to the moisture in atmosphere and gives rise to decrease with humidity.

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Cosensitization effects of polyphenylene compounds (PP) such as biphenyl (BP), terphenyls (o-, m-, p-TP), and phenanthrene (Phen) in photoinduced electron-transfer reactions were examined. The 9,10-dicyanoanthracene (DCA)-sensitized cis-trans photoisomerization of 1,2-bis(4-methoxyphenyl)cyclopropane (CP), which proceeds in a chain reaction via free radical cation of CP (CP •+ ) as a chain carrier, was accelerated by adding PP, particularly by TP. A similar accelerating effect was observed in the DCA-sensitized photooxygenation of CP as another example. BP and TP were more stable under the oxygenation condition than phenanthrene and naphthalene, which also accelerate the photooxygenation CP. CP •+ is generated by the direct electron transfer from CP to the excited singlet state of DCA ( 1 DCA*) and also by the secondary electron transfer from CP to PP •+ , which is generated by the primary electron transfer from PP to 1 DCA*. The laser flash photolysis study revealed that the quantum yield for the formation of free CP •+ in the direct electron transfer from CP to 1 DCA* (Φ CP •+ ≈ 0.1) was smaller than that in the presence of PP. This is due to the high yield of free PP •+ generation by the primary electron transfer and the efficient secondary electron transfer from CP to PP •+ . The secondary electron transfers were found to take place in nearly diffusion-controlled rates (0.9-1.5 × 10 10 M -1 s -1 ). The high yield of PP •+ as free radical ions does not seem to be the sole factor of the cosensitization of PP for the DCA-sensitized photoreactions of CP. The ratio of the quantum yields of the photoreactions to that of the initial CP •+ formation (turnover) also increased by the addition of PP from 3 (isomerization) and 15 (oxygenation) to 32-90 for both reactions. The second-order rate constant for the decay of CP •+ in aerated acetonitrile was decreased by a factor of 0.5-0.8 by the addition of PP. We concluded that the cosensitization effect in the photoreaction involves a π-complex formation between CP •+ and PP assisting the chain reaction as well as initial CP •+ formation.