Tuning of the color of the emitted light from new polyperyleneimides containing oxadiazole and siloxane moieties

Abstract

Four new aromatic poly(peryleneimides) containing electron-withdrawing oxadiazole rings and flexible tetramethyldisiloxane units in the backbone were prepared by a one step polycondensation reaction at high temperature of four aromatic diamines containing preformed oxadiazole units with a mixture, in different ratios, of perylenetetracarboxylic dianhydride and tetramethyldisiloxane-1,3-bis(4-phthalic anhydride). The structure of these polymers was confirmed by FT-IR and 1H NMR spectroscopy. The solubility, thermal stability and glass transition temperature of the poly(peryleneimides) were measured and discussed in correlation with their chemical structure. The solid polymers were studied by X-ray diffraction which revealed a semicrystalline state consisting in face-to-face arranged columns of perylenediimide units for two of the polymers. The film-forming ability and the morphology of the resulting thin films were investigated using scanning electron microscopy which showed that two of the polymer films were organized into self-assembled rod-like structures. An extensive study of the photo-optical properties of these polymers highlighted the ability of the color of the emitted light to be modulated as a function of the excitation wavelengths, as was surveyed in the chromaticity diagrams. The Förster excitation energy transfer phenomenon from oxadiazole to perylenediimide chromophores was observed to occur for some of the polymers, for which the oxygen bridge appears to be responsible. In solution, high fluorescence quantum yields were obtained, up to 24%, while, in the solid state, low fluorescence emission was attained due to aggregation. These poly(peryleneimides) could be considered as promising candidates for high-performance materials to be used in novel optoelectronic applications, e.g. chemiluminescent sensors.