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Durham University

Department of Physics

Staff profile

Publication details for Associate Professor Fernando Dias

Dias, FB, Knaapila, M, Monkman, AP & Burrows, HD (2006). 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. Macromolecules 39(4): 1598-1606.
  • Publication type: Journal Article
  • ISSN/ISBN: 0024-9297
  • Keywords: PHOTON-HARVESTING POLYMERS; MAXIMUM-ENTROPY METHOD; ENERGY-TRANSFER; LIFETIME DISTRIBUTIONS; GREEN EMISSION; LUMINESCENCE; DYNAMICS; MIGRATION; CHAIN; POLYTHIOPHENE

Author(s) from Durham

Abstract

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.