Intermolecular structure in a single component polymer glass: Towards high resolution measurements of the sidechain pair correlation function

Abstract

Electronic excitation transport among interacting polymer molecules lightly tagged with chromophore substituents is theoretically examined as a function of tagged polymer concentration in the polymeric solid. The results are compared to experimental data obtained in a previous study [Macromolecules 26, 3041 (1993)]. The dependence of time-resolved fluorescence observables on intermolecular polymer structure is of primary interest. A theory is presented which describes excitation transport for both donor–donor (DD) and donor–trap (DT) systems. For the case of DD transport, the theory is based on a first order cumulant approximation to the transport master equation. For DT transport, the theory does not involve approximations and is an exact representation of the assumed model. In both cases, the model makes use of the Flory ‘‘ideality’’ postulate by depicting the intramolecular segmental distribution as a Gaussian with a second moment that scales linearly with chain size. The only adjustable parameter in the treatment is the form of the intermolecular segmental pair distribution function g(r). The model is found to be extremely sensitive to the behavior of g(r). Comparisons to experimental data indicate that g(r) is primarily made up of hard core interactions between the chromophore sites. The DT calculations display a higher sensitivity to the form of g(r) than the corresponding DD calculations. For purposes of comparison, the analysis is applied to a DT system in which every polymer chain has chromophore tags. The sensitivity of the method for 100% tagged systems to g(r) is comparable to the analysis for systems with only some of the chains tagged.