title: Raman spectroscopy of intermolecular charge transfer complex between a conjugated polymer and an organic acceptor molecule.
abstract: Intermolecular donor-acceptor charge transfer complex (CTC) formed in the electronic ground state between poly[2-methoxy-5-(2-ethylhexyloxy)-1,4-phenylenevinylene] (MEH-PPV) and 2,4,7-trinitrofluorenone (TNF) has been investigated by Raman and optical absorption spectroscopies. Blending of MEH-PPV and TNF results in appearance of the CTC absorption band in the optical gap of the both components and in changes in the characteristic MEH-PPV Raman bands including shifts, change in bandwidth, and intensity. The experimental data are similar in films and solutions indicating the CTC formation in both. We associate the low-frequency shift of the strongest MEH-PPV Raman band at approximately 1580 cm(-1) reaching 5 cm(-1) with partial electron transfer from MEH-PPV to TNF amounting approximately 0.2e(-). We suggest that polymer conjugated segments can form the CTC of variable composition MEH-PPV:TNF=1:X, where X<or=0.5 is per MEH-PPV monomer unit. Our Raman data indicate that MEH-PPV conjugated segments involved in the CTC become more planar; however, their conjugation length seemingly does not change.
authors.affiliation: Faculty of Physics and International Laser Center, Lomonosov Moscow State University, Moscow 119992, Russia.
authors.forename: V V
authors.initials: VV
authors.lastname: Bruevich
authors.forename: T Sh
authors.initials: TSh
authors.lastname: Makhmutov
authors.forename: S G
authors.initials: SG
authors.lastname: Elizarov
authors.forename: E M
authors.initials: EM
authors.lastname: Nechvolodova
authors.forename: D Yu
authors.initials: DY
authors.lastname: Paraschuk