Decoupling 2D inter- and intrachain energy transfer in conjugated polymers.

The dimensionality of conjugated polymer systems plays an important role in energy-transfer processes, and 1D and 2D energy transfer of excitations are typically much slower than that between pi-stacked chains within a 3D polymeric solid. However, whether 2D energy transfer in conjugated polymers occurs mainly along polymer chains (intrachain), or between in-plain-adjacent polymer chains (interchain), has yet to be determined due to the difficulty of experimentally decoupling inter- and intrachain interaction in a 2D polymer system. This can be achieved by incorporating conjugated polymer chains into the planar galleries of layered matrices which sterically hinder polymer aggregation and pi-pi interchain interactions. Here, pristine blue-emitting polyfluorene chains and polyfluorene chains with known concentrations of green-emitting on-chain fluorenone defects are either separately or collectively incorporated into layered SnS(2). X-ray powder diffraction of the composite films confirms incorporation of the polymer chains into the layered galleries. Monitoring the fluorene-to-fluorenone energy transfer as a function of fluorenone concentration and distribution in the layered galleries allows differentiation between inter- and intrachain fluorene-fluorenone energy transfer. It is found that, 2D energy transfer in conjugated polymers follows mainly an interchain process, despite the absence of pi-pi interchain interactions.