Discriminated structural behaviour of C60 and C70 peapods under extreme conditions

We studied structural changes in C-60 and C-70 peapods - i. e. C-60 and C-70 chains inserted inside single- walled carbon nanotubes - when submitted to high pressure and temperature conditions. X- ray diffraction experiments showed that while C-60 molecules polymerize inside nanotubes at pressures and temperatures consistent with polymerization in bulk C-60 phases, no polymerization is observed in C-70 peapods, even at pressures and temperatures above the threshold for polymerization in bulk C-70. Tubular confinement in the nanotube container prevents the monomers to rearrange in the way needed for polymerization. This result testifies for the strong influence of con. nement on the behaviour of C-70.