Structure of poly(p-hydroxystyrene) film

Pyrene-doped poly(p-hydroxystyrene) (PHST) thin films prepared by spin- coating method are studied by time-resolved total-internal-reflection fluorescence spectroscopy. We observed inhomogeneity such as a concentration gradient of doped pyrene molecules and a gradient of polarity (hydrophobicity), and also the existence of isolated pyrene molecules. Stable ground-state dimers of pyrene are found in surface, bulk, and interface layers of a PHST film. These features cause the complicated rise and decay of fluorescence. These results also depend upon the preparing process such as the baking condition.