| Research Abstract |
Photoinduced electron transfer (PIED between ruthenium tris(2 ,2'-bipyridyl) complex (Ru(bpy)_3^<2+>) and electroactlve materials has been studied extensively from the stand point of artificial photosynthesis and photoenergy conversion. Since Ru(bpy)_3^<2+> can be regenerated in the presence of appropriate sacrificial agents, it acts as a photocatalyst. We have already reported hotopolymerization of aniline and an aniline dimer, i.e. , AF-phenyl-p-phenylenediamine (PPD), by illuminating a bilayer film composed of Ru(bpy)_3^<2+>-incorporated Naflon and methylviologen (MV^<2+>)-pendant poly(siloxane) or a single layer film composed of Ru(bpy)_3^<2+>- and MV^<2+>-incorporated Flemion. Clay minerals have anionically-charged interlayers and intercalate, by cation exchange, positively-charged organic molecules in their interlayer spaces. We thus intercalated Ru(bpy)_3^<2+> and protonated PPD in a hectorite clay, i.e., Ionite H (INT), in acidic aqueous solution and examined photopolymerizatio
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n of PPD by Ru(bpy)_3^<2+> in the two-dimensional interlayer spaces. We found that the anionically-charged clay layers act as templates and also as counter ions for the acid-doped conducting form of polyaniline(PAn) formed, giving linear conductive PAn with long conjugation.
The template and acid-doping effects of other types of polyanionic materials in photocatalytic polymerization of PPD were also examined. Potasium polyvinylsulfate (PVSK), a flexible polyanion, afforded a PAn/PVSK complex which is soluble either in water or in an organic solvent, depending upon the molar ratio of PPD and PVSK. Sodium dodecyl sulfate (SDS), a micelle-forming anionic surfactant, gave a complex similar to that given by INT, the micellar surface apparently acting as a two-dimensional template as the clay interlayer. DNA, a rigid double-helical polyanion, on the other hand, afforded a linear acid-doped PAn even at less acidic pH, i.e.,pH 3-6. Emergence of circular dichroism in the absorption band of PPD suggests alignment of PPD molecules in the local lower pH environment provided by DNA, leading to formation of expanded-coil PAn in the PAn/DNA complex. Additionally, image formation on the Flemion film as well as application of a PAn/DNA/Ru(bpy)_3^<2+> complex as a light emitting diode was also examined. Less
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