Jps. Farinha et al., Interfaces in self-assembling diblock copolymer systems: Characterization of poly(isoprene-b-methyl methacrylate) micelles in acetonitrile, J PHYS CH B, 103(13), 1999, pp. 2487-2495
The kinetics of dipolar nonradiative energy transfer (DET) between dyes con
fined to the core-corona interface region of poly(isoprene-b-methyl methacr
ylate) block copolymers (PI-PMMA) in acetonitrile was analyzed using a new
distribution model for energy transfer in spherical micelles. The distribut
ion of block junction points was described by the model of Helfand and Taga
mi (HT) for the strong segregation limit, adapted for the spherical geometr
y of the core-corona interface. We used this model to analyze experimental
fluorescence decay curves for block copolymer micelles made up of polymers
containing a donor dye or an acceptor dye covalently attached to the PI-PMM
A junction. The analysis yielded an interface thickness between the PI core
and the PMMA corona of delta = (0.9 +/- 0.1) nm. In the past, the experime
ntal fluorescence decay curves measured for similar systems have been fitte
d with the Klafter and Blumen (KB) equation for energy transfer, which has
a stretched exponential form. To relate these results to topological charac
teristics of the system, we simulated donor decay profiles for different in
terface thickness values using the new distribution model for energy transf
er and a modified HT equation. Subsequent analysis by the stretched exponen
tial KB equation proved that the magnitude of the fitted exponent is direct
ly related to the interface thickness between the blocks for a given dye co
ncentration in the core-corona interface. Within a certain range of interfa
ce thickness values, this relation can be used to determine the interface t
hickness from the fitting parameters of the KB equation.