Transformation of C70 peapods into double walled carbon nanotubes

X-ray diffraction studies comparing the transformation of C60 and C70 peapods into double walled carbon nanotubes are presented. The structures of the as-formed DWCNTs are strikingly similar, showing that they are not dependent on the nature of the fullerene precursor. High temperature X-ray diffraction measurements of C70 peapods below the coalescence temperature show that confined C70 molecules in large tubes undergo an orientational transition to free rotations. Fast re-orientations of C70 molecules allow cyclo-addition between adjacent fullerenes to form, in good agreement with the mechanism of coalescence proposed in the literature for C60 molecules.