Electronic energy transfer in polymers labeled at both ends with fluorescent groups

The energy transfer between chromophores attached at the ends of an isolated polymer chain was studied. Chains labeled with different or equal fluorophores at the ends were considered. Interpolated analytical expressions dependent on a unique parameter, were derived for the fluorescence decay curves taking into account the distribution of end-to-end separations in both 0 and good solvents for the polymer. The donor decay curves for chains with dissimilar chromophores were compared with the exact solution obtained by numerical integration. The derived expressions reproduce the decay for all times with a precision better than 1% for pseudo-ideal chains (theta solvents) and 3% for chains in good solvents. The inhomogeneous broadening of chromophore spectra is important when its width is larger than 20% of the homogeneous broadening width. The fluorescence decay curves in the presence of Brownian motion were also calculated after solving the Smoluchowski diffusion equation for the end-to-end separation distance distribution function. Chain dynamics is important for donors with long lifetimes, high diffusion coefficients and donor-acceptor pairs with small Forster radius. (C) 2002 Elsevier Science B.V. All rights reserved.