Visualizing spatial and temporal heterogeneity of single molecule rotational diffusion in a glassy polymer by defocused wide-field imaging

Defocused wide-field fluorescence microscopy was used to follow the 3D molecular rotational diffusion of a fluorescent probe molecule in a polymer thin film. The technique allows for visualizing the molecular reorientation both in-plane and out-of-plane. The local environmental change driven by heterogeneous dynamics of the polymer can be probed on a scale of 1 μm as demonstrated by parallel imaging of several molecules. A multi-component rotational diffusion decay is observed which might reflect both different relaxation regimes of the polymer as well as rapid changes of the local environment.