Microscale polarity in polymer films probed by fluorescence of a benzanthrone derivative on ensemble and single-molecule level

We report fluorescence lifetime studies of a charge-transfer dye, dimethyl-amino-N-acetyl-3-aminobenzanthrone, embedded in a series of polymer matrices. In all polymers studied, the fluorescence lifetime has two components, indicating the existence of two classes of molecular environments. Microscopic studies on sub-ensembles of the dye molecules carried out in PMMA and PVAc matrices reveal that the polymer films are spatially heterogeneous with respect to their physical properties on scales of more than few hundreds of nm. The heterogeneity further increases on molecular scale, as observed by fluorescence lifetime distribution of the dye in the PMMA matrix.