The 13 C nuclear magnetic resonance (NMR) and dielectric behavior of rhombohedral C 60 polymer with (003) texturing have been studied. 13 C NMR reveals that sp 3 bonds break from 423 to 523K. This is the temperature region in which depolymerization occurs, as deduced from temperature-resolved X-ray diffractometry. X-ray diffraction also shows the structural transition from rhombohedral to face-centered cubic structure at 530K. This indicated a 0.1Å increment in the c-axis lattice parameter, attributable to the conversion of the elongated C 60 cages to spherical C 60 before the structural transition. The elongation arises from intermolecular sp 3 bonds. Strain relaxation should take place when these break during depolymerization, and we give experimental proof that this occurs. The polymer’s AC impedance varies with temperature, and frequency-dependent peaks are found over the same temperature range of 423–523K, these peaks disappearing in depolymerized samples. This dielectric relaxation has a thermal activation energy of 1.2±0.1eV, which may be interpreted as the potential barrier for the dissociation of cage-linking sp 3 bonds. Possible origins of the electric dipoles responsible for dielectric relaxation are proposed.