Characterization of Chain Motion and Phase Structure of Aromatic Waterborne Polyurethane Film Using Intrinsic Fluorescence Spectra

The phase structure and macromolecular chain motion of aromatic waterborne polyurethane film were examined by the fluorescence technique. Excimer emission of the phenyls appears at 436 and 468 nm and is temperature dependent, suggesting that the hard segments in the intermediate phase can be locally oriented. Binding energy of the excimer structure determined by the intrinsic fluorescence spectra is 16 kJ/mol. The intrinsic fluorescence technique can supply more information than the DSC method on segment relaxations, including α-relaxation for the hard or soft segments, β-relaxation of small molecular units, crystallization of the soft segments, γ-relaxation of the classical consecutive –CH2– units, and even phase separation degree.