Spectroscopy and Imaging

A series of methacrylates containing rigid π-conjugated oligo(phenylene ethynylenes) with different size of the conjugated system (M I – M III) and therefore optoelectronic properties were synthesized in order to form adequate systems designed for resonance energy transfer (RET).. The monomers were polymerized by the reversible addition-fragmentation chain transfer (RAFT) polymerization (P I – P III). The polymers were characterized by 1H NMR spectroscopy and elemental analysis. Furthermore, the molar masses of the polymers were determined by size exclusion chromatography (SEC) and analytical ultracentrifugation (AUC). The photophysical properties of the polymers were studied by UV-vis and emission spectroscopy in diluted solutions as well as in thin films in comparison of the photophysics of the the corresponding monomers. Thereby changes going from monomeric to polymeric systems are detected in fluorescence quantum yields and lifetimes pointing to energy trapping e.g. energy transfer. Donor-acceptor-copolymers containing different numbers of monomeric units within the side chain exhibit differences in the time resolved emission spectra, indicating that energy trapping in polymers is very sensitive to structural properties such as chain the length. In addition, the film formation behavior of all polymers was investigated by confocal microscopy and atomic force microscopy (AFM). Finally, P IIb was tested as proof-of-principle as the active layer material in an organic solar cell device. Moreover, a statistical donor- acceptor copolymer (P II-stat-P III) was synthesized and characterized. UV-vis absorption spectroscopy as well as as well as time resolved lifetime studies indicate intra- and interpolymer energy transfer.