INTERMOLECULAR STRUCTURE IN A SINGLE-COMPONENT POLYMER GLASS - TOWARDS HIGH-RESOLUTION MEASUREMENTS OF THE SIDE-CHAIN PAIR CORRELATION-FUNCTION

Electronic excitation transport among interacting polymer molecules li ghtly tagged with chromophore substituents is theoretically examined a s a function of tagged polymer concentration in the polymeric solid. T he results are compared to experimental data obtained in a previous st udy [Macromolecules 26, 3041 (1993)]. The dependence of time-resolved fluorescence observables on intermolecular polymer structure is of pri mary interest. A theory is presented which describes excitation transp ort for both donor-donor (DD) and donor-trap (DT) systems. For the cas e of DD transport, the theory is based on a first order cumulant appro ximation to the transport master equation. For DT transport, the theor y does not involve approximations and is an exact representation of th e assumed model. Ln both cases, the model makes use of the Flory ''ide ality'' postulate by depicting the intramolecular segmental distributi on as a Gaussian with a second moment that scales linearly with chain size. The only adjustable parameter in the treatment is the form of th e intermolecular segmental pair distribution function g(r). The model is found to be extremely sensitive to the behavior of g(r). Comparison s 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 correspondin g 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 comparab le to the analysis for systems with only some of the chains tagged.