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Infrared Spectroscopic Signatures of Phase Segregation in P3HT−Porphyrin Blends

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journal contribution
posted on 05.11.2009, 00:00 by Audrey A. Eigner, Patrick E. Konold, Aaron M. Massari
Phase segregation of 2,3,7,8,12,13,17,18-octaethyl-21H,23H-porphine ruthenium(II)carbonyl (RuOEP) and regioregular poly(3-hexylthiophene-2,5-diyl) (P3HT) in thin films is investigated with infrared and UV−visible spectroscopies as well as transmission electron microscopy (TEM). The Fourier transform infrared (FTIR) spectrum of the ruthenium-bound CO symmetric stretching mode exhibits significant changes as these films are annealed in solvent vapors. The development of multiple inhomogeneously broadened microenvironments is observed, and UV−visible spectra and TEM support a model of homogeneous porphyrin distribution throughout the P3HT films that gradually becomes more heterogeneous as the P3HT and RuOEP molecules phase segregate. A complete model for the phase segregation process experienced by the embedded RuOEP is proposed to explain the collective experimental observations.