Interactions between fullerene(C60) and poly(ethylene oxide) in their complexes as revealed by high-resolution solid-state 13C NMR spectroscopy

A series of poly(ethylene oxide) (PEO)/fullerene(C60) complexes are prepared by lyophilization. The intermolecular interaction and molecular motion in the complex are investigated by solid-state 13C NMR spectroscopy. An intense C60 signal due to the intermolecular cross-polarization is observed in the 13C CP/MAS spectra of the complex samples, indicating a high degree of dispersion of C60s in the complexes. By measuring the 13C spin-lattice relaxation times and 1H transverse relaxation times of the complex sample and by comparing the static 13C spectrum of the pure C60 sample with that of the complex sample, it is demonstrated that there exist n–π interactions between the n-orbitals of the PEO ether oxygen and the π-system of C60. The C60 molecules act as physical cross-links in the amorphous region of PEO, which greatly inhibit the mobility of the surrounding PEO chains, while the rapid isotropic rotation of C60 molecules is also reduced to some extent due to the interactions with the polymer chains. [Copyright &y& Elsevier]