Abstract
Europium(III) (Eu^3+^)‐doped polyurethane films were prepared by mixing Eu‐methacrylic acid complex (Eu(MA)~3~) with aliphatic polyurethane oligomer and subsequently curing under UV irradiation. Transmission electron microscopy photos and the appearance of the resulting hybrid films showed that phase separation occurred only at an Eu(MA)~3~ content above 20 wt.‐%. Fluorescence spectra indicated that the fluorescence of Eu^3+^ was barely influenced by the polyurethane matrix and its intensity increased with an Eu(MA)~3~ content in the range of approximately 0 to 10 wt.‐%. An obvious applied external‐field‐dependent magnetization (M) of polyurethane/Eu(MA)~3~ films, namely, an increasing M at low field and a decreasing M at high field, was observed at room temperature from the hysteresis loops, which was influenced by both the Eu(MA)~3~ content and the ultrasonication imposed on the coatings before curing. It seems that ultrasonication leads to a thermodynamically‐unstable structure of Eu^3+^ in hybrid films, which can be fixed by UV curing but gradually rearranges to its original form during the thermal‐curing process, and enhances the diamagnetic part of the hybrid film. Thus, the magnetic property of Eu^3+^‐doped polyurethane film at room temperature can be adjusted by simply changing the preparation method and the Eu(MA)~3~ content instead of the type of Eu^3+^‐organic complex.
magnified image