Single-molecule fluorescence spectroscopy is employed to reveal 3D details of the mechanisms underpinning ion transport in a polyelectrolyte thin film possessing polymer-brush nanoscale order. The ability to resolve fluorescence emission over three discrete polarization angles reveals that these ordered materials impart 3D orientation to charged, diffusing molecules. The experiments, supported by simulations, report global orientation parameters for molecular transport, track dipole angle progressions over time, and identify a unique transport mechanism: translational diffusion with restricted rotation. In general, realization of this experimental method for translational diffusion in systems exhibiting basic orientation should lend itself to evaluation of transport in a variety of important, ordered, functional materials.
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