Monte Carlo simulations of electronic excitation transfer in polymer composites and comparison to theory

Abstract

A Monte Carlo simulation of polymer/polymer interface in the presence of block copolymer. I. Effects of the chain length of block copolymer and interaction energy Monte Carlo ͑MC͒ simulations of electronic excitation transfer ͑EET͒ among a small number of chromophores covalently incorporated into copolymer molecules are presented and used to test the results of previously developed analytical EET theories that are useful for the study of polymer chain structure ͓K. A. Peterson and M. D. Fayer, J. Chem. Phys. 85, 4702 ͑1986͔͒ and phase separation in polymer blends ͓A. H. Marcus and M. D. Fayer, J. Chem. Phys. 94, 5622 ͑1991͔͒. The simulations and theory account for EET among chromophores bound to a single chain and among chromophores attached to different chains. The calculated quantity, ͗G s (t)͘, which is the probability that an initially excited chromophore is still excited at time t, is related to time-resolved fluorescence depolarization experiments. The theories, particularly the treatment of interchain EET, depend on a series of approximations whose efficacy has not been determined. Close agreement between the MC simulations and the analytical theory are found for a variety of situations, including those that mimic real polymer systems. The limits beyond which agreement is weakened provide specific guidelines for the design of polymer structure and phase-separation experiments.

Hydrodynamic effects on the extension of stars and dendrimers in external fields

“…2 could be observable in experiments which monitor the local structure, such as electronic energy transfer or even NMR. [52][53][54][55][56][57][58][59][60][61][62] One should keep in mind that the Zimm model considered here is an extreme case; we expect in experiments the dynamical behavior to be intermediate between f r = 0 and f r = 0.25, so that the particular form of the pY Ã N P will lie between the Rouse and the Zimm results displayed here.…”

“…Similarly, the longest relaxation time in the Rouse case goes as rs R 2Yf = 4X1 N 10 3 for all f. One may note that going from f = 2 (or 3) to f = 6 the extension of the star grows roughly by a factor of 1/3 (or 1/7), facts readily detectable by fluorescent means. [53][54][55][56][57][58][59] In Fig. 4 we again consider pY Ã tP À Y Ã DC t the extension of the star, but now for a fixed number of beads, N = 601.…”

Phase Separation in Binary and Ternary Polymer Composites Studied with Electronic Excitation Transport

“…14 This theory has been shown to be accurate through experiments 15 and comparison to detailed simulations. 5,8 An analytical theory was also developed for interchain EET, i.e., the contribution to 〈G s (t)〉 from excitations that transfer from chromophores on copolymer chains containing the initially excited chromophores to chromophores on other copolymer chains. 16 The initial development of the theoretical method treating interchain transfer was subsequently corrected and tested with Monte Carlo simulations.…”

“…This technique can reveal the single-chain structure and spatial distribution of polymer chains in a blend on a nanometer distance scale. Monte Carlo simulations, in which the likelihood of finding an excitation on an initially excited chromophore at time t is determined for various chromophore distributions, can be used to analyze the measured decay of the polarization anisotropy of the emitted fluorescence, r ( t ), in terms of the characteristics of the polymer system …”

Nonisotropic Excitation Energy Transport in Organized Molecular Systems: Monte Carlo Simulation-Based Analysis of Fluorescence and Fluorescence Anisotropy Decay

“…simulation method. 7,15,16 Although this method has been used extensively to test the validity of the approximations made in analytical theories, [17][18][19][20] its possibilities stretch much further, as is demonstrated in this work.…”