ORIENTATION OF PORPHYRIN MOIETIES IN LANGMUIR-BLODGETT-FILMS OF TETRAPHENYLPORPHYRIN VINYL MONOMERS AND THEIR POLYMERS

The monolayer behavior and formation of Langmuir-Blodgett (LB) films w ere compared between the vinyl monomers of silver(Ir) tetraphenylporph yrin (AgTPP) and their polymers. In both cases, eicosanoic acid was mi xed at [eicosanoic acid]/[AgTPP unit] = 1.5 ratio to reduce the aggreg ation of the porphyrins. From the isotherms of the monolayers at an ai r-water interface, the porphyrin moieties in the monomers occupied a l arger area than those in the polymers. It indicated that the porphyrin groups were more compact in the polymers because they were attached t o a polymer chain. Applying the electron spin resonance and polarized UV-vis absorption spectroscopies for the LB films deposited on a hydro phobic glass plate, the orientation of the AgTPP moieties was estimate d. As a result, three orientations of porphyrin planes existed in the monomer films: the angle between the film normal and the transition di pole (or the porphyrin plane), phi, was 90 degrees for one orientation and 39-59 degrees far the other two orientations. Two orientations ex isted in the polymer films: phi was 39-59 degrees for these two. The p orphyrin whose plane oriented at phi = 90 degrees was considered to be the one that was squeezed out of the fatty acid layers. Such porphyri n moieties did not exist in the polymer films. These results have show n that the polymer main chain plays an important role in stabilizing t he orientation of porphyrin moieties.