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transfer across a polymer–polymer interface can be highly
heterogeneous as a result of morphological features at the
interface. Furthermore, the results demonstrate that the
morphology of the chains that comprise the diblock can
differ substantially from the morphology of the separate
homopolymers.
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Experimental Section
Dilute thin-film samples of poly(2-methoxy,5-(2’-ethylhexyloxy)-p-
phenylenevinylene)-co-poly(2-dimethyloctylsilyl-p-phenylenevinyl-
ene) (DMOS-co-MEH; MW = 312 kDa, polydispersity index: 1.18)
were prepared according to a reported procedure,[19] and the synthesis
and characterization of DMOS/MEH are described in detail in the
Supporting Information. Typically, samples were diluted in a solution
of PMMA (3% w/w) in toluene and spin-cast onto glass substrates to
yield films of approximately 100-nm thickness. Samples were then
coated with either gold or aluminum ( ꢀ 200 nm) to prevent oxygen
and water from diffusing into the PMMA layer. Single molecules
were excited with the doubled output (415 nm) of a Ti:sapphire laser
centered at 830 nm, and the 457.9 nm and 488 nm lines of an argon-
ion laser and images and spectra were obtained from a confocal
scanning microscope apparatus described elsewhere.[19] Excitation
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[23] The expression for energy-transfer efficiency is given by: EET
=
fDA
1À , where fD and fDA are the quantum yields of the donor
fD
and donor-acceptor ensemble, respectively. Owing to lack of
experimental data on the emission quantum yields, apparent
efficiencies of energy transfer (1ÀfD) were determined here
using relative intensities.
intensities were approximately 200 WcmÀ2
.
[24] D. Hu, J. Yu, P. F. Barbara, J. Am. Chem. Soc. 1999, 121, 6936.
Received: April 21, 2005
Revised: June 15, 2005
Published online: September 1, 2005
Keywords: energy transfer · fluorescence · interfaces ·
.
polymers · single-molecule studies
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