Title: Spectroscopic Properties, Excitation, and Electron Transfer in an Anionic Water-Soluble Poly(fluorene-alt-phenylene)-perylenediimide Copolymer
Authors: Marques, Ana T ×
Burrows, Hugh D
Sergio Seixas de Melo, J
Valente, Artur J M
Justino, Licínia L G
Scherf, Ullrich
Fron, Eduard
Rocha, Susana
Hofkens, Johan
Snedden, Edward W
Monkman, Andrew P #
Issue Date: Jun-2012
Publisher: American Chemical Society
Series Title: Journal of Physical Chemistry B vol:116 issue:25 pages:7548-7559
Abstract: An anionic fluorene-phenylene poly{1,4-phenylene-[9,9-bis(4-phenoxy-butylsulfonate)]fluorene-2,7-diyl}-based copolymer containing on-chain perylenediimine (PDI) chromophoric units, PBS-PFP-PDI, was synthesized and its photophysical properties studied as aggregates and isolated chains in water and dioxane/water (1:1) solution. UV-vis and emission spectroscopy measurements, time-correlated single photon counting, and wide field imaging have been employed to investigate the excited-state behavior of the PBS-PFP-PDI copolymer, including the effect of environment on the energy and electron transfer to the on-chain PDI chromophore. Although the Forster overlap integral is favorable, no evidence is found for intramolecular singlet excitation energy transfer in isolated copolymer chains in solution. Fluorescence is suggested to involve an interchain process, thus revealing that isolated copolymer chains in solution do not undergo efficient intramolecular energy transfer. However, quenching of the PBS-PFP excited state by PDI is observed in aqueous media and ultrafast pump-probe studies in water or dioxane-water solutions show that electron transfer occurs from the phenylene-fluorene units to the PDI. The extent of electron transfer increases with aggregation, suggesting it is largely an interchain process. The interaction of the negatively charged PBS-PFP-PDI copolymer with the positively charged surfactant hexadecyltrimethylammonium bromide (CTAB) in solution has also been studied. The copolymer PBS-PFP-PDI aggregates with the surfactant already at concentrations below the critical micelle concentration (cmc) and the nonpolar environment allows intermolecular energy transfer, observed by the weak emission band located at 630 nm that is associated with the emission of the PDI chromophore. However, the fact that the PDI photoluminescence (PL) lifetime (similar to 1.4 ns) obtained in the presence of CTAB is considerably shorter than that of the nonaggregated chromophore (similar to 5.4 ns) suggests that even in this case there is considerable PL quenching, possibly through some charge transfer route. The increase of the PBS-PFP-PDI photoluminescence intensity at surfactant concentrations above the cmc indicates deaggregation of polyelectrolyte within the initially formed polyelectrolyte-surfactant aggregates.
ISSN: 1520-6106
Publication status: published
KU Leuven publication type: IT
Appears in Collections:Molecular Imaging and Photonics
× corresponding author
# (joint) last author

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