Interactions between fullerene(C 60) and poly(ethylene oxide) in their complexes as revealed by high-resolution solid-state 13C NMR spectroscopy

Abstract

A series of poly(ethylene oxide) (PEO)/fullerene(C 60) complexes are prepared by lyophilization. The intermolecular interaction and molecular motion in the complex are investigated by solid-state 13C NMR spectroscopy. An intense C 60 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 C 60s 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 C 60 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 C 60. The C 60 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 C 60 molecules is also reduced to some extent due to the interactions with the polymer chains.