Eu(III) modifies the properties of poly(N-isopropylacrylamide)

A novel functional complex of poly(N-isopropylacrylamide) and Eu(III) (PNIPAM–Eu(III)) with thermosensitive and fluorescent properties was synthesized and characterized by X-ray photoelectron spectroscopy (XPS), differential scanning calorimetry (DSC), and fluorescence spectroscopy. The results from the experiments indicated that Eu(III) is bonded to nitrogen and oxygen atoms in the polymer chain of PNIPAM and formed the complex of PNIPAM–Eu(III). The maximum emission intensity of PNIPAM–Eu(III) at 614 nm is enhanced about 22 times compared with that of the corresponding Eu(III), demonstrating that there exists an efficient intermolecular energy transfer from the polymer ligand to Eu(III). Nevertheless, the lower critical solution temperature of PNIPAM containing a low content of Eu(III) has not obviously changed after the formation of the complex of PNIPAM–Eu(III) by the interaction between PNIPAM and Eu(III).