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https://hdl.handle.net/10316/10453
Título: | Fast and Slow Time Regimes of Fluorescence Quenching in Conjugated Polyfluorene−Fluorenone Random Copolymers: The Role of Exciton Hopping and Dexter Transfer along the Polymer Backbone | Autor: | Dias, Fernando B. Knaapila, Matti Monkman, Andrew P. Burrows, Hugh D. |
Data: | 21-Fev-2006 | Editora: | American Chemical Society | Citação: | Macromolecules. 39:4 (2006) 1598-1606 | Resumo: | The luminescence decay kinetics of polyfluorene copolymers containing fluorenone units randomly distributed along the polymer chain have been studied by steady-state and time-resolved fluorescence techniques in toluene solution. The typical green emission from polyfluorenes containing 9-fluorenone moieties is only observed if the 9-fluorenone group is covalently attached to the polymer. Small-angle neutron scattering (SANS) measurements indicate that, independent of the 9-fluorenone fraction, all the studied copolymers adopt an open wormlike conformation. This prevalent 1-dimensional arrangement confirms that the green emission observed with polyfluorenes is not the result of excimer formation in the typical sandwich-like conformation. Analysis of time-resolved fluorescence decays by the maximum entropy method (MEM) collected at the polyfluorene emission (415 nm) and by global analysis of decays collected at 415 and 580 nm (the 9-fluorenone defect emission wavelength) clearly indicates two different time regimes in the population of the fluorenone defect: one occurring in the time interval of 10 to 30 ps and a second one occurring in the time range from 70 to 200 ps. While the slower process shows a linear dependence with the 9-fluorenone fraction, compatible with a hopping migration process along the polymer chain, the faster process does not show such a dependence and instead suggests a short-range Dexter mechanism. These findings are in agreement with our previous work where the presence of a faster component was suggested. | URI: | https://hdl.handle.net/10316/10453 | ISSN: | 0024-9297 | DOI: | 10.1021/ma052505l | Direitos: | openAccess |
Aparece nas coleções: | FCTUC Química - Artigos em Revistas Internacionais |
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Fast and Slow Time Regimes of Fluorescence Quenching.pdf | 195.35 kB | Adobe PDF | Ver/Abrir |
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