Fluorescence Study of Energy Transfer in PMMA Polymers with pendant Oligo-Phenylene-Ethynylenes

A spectroscopic characterization of polymers containing rigid π-conjugated oligo (phenyleneethynylene) chromophores as well as oligo(phenyleneethynylene) and methyl methacrylate is presented. The polymers exhibit molar masses up to 15000 g/mol and a degree of polymerization between 22 and 80. Emission measurements of the monomeric and polymeric species showed that radiative as well as nonradiative rates are influenced by the degree of polymerization due to intramolecular interactions of chromophores pendant to the polymer backbone. Time-resolved emission-anisotropy measurements suggest that energy migrates within the polymers. In addition, steady-state emission-anisotropy measurements point to energy migration. Additionally, two oligo(phenyleneethynylene)s with different sizes of the conjugated system have been copolymerized in order to enable energy trapping due to energy transfer. The shortened energy donor fluorescence lifetime within the donor-acceptor copolymers suggest energy transfer. Depending on the degree of polymerization dispersion of the donor fluorescence lifetime is observed.