Discriminated structural behaviour of and peapods under extreme conditions

¹  Laboratoire de Physique des Solides UMR-8502 CNRS, Université Paris-Sud - F-91405 Orsay, France
²  Department of Physics, Umeå University - S-90187 Umeå, Sweden
³  Centre d' Elaboration des Matériaux et d'Etudes Structurales, UPR-8011 CNRS - F-31062 Toulouse, France
⁴  Institut Laue Langevin - F-38042, Grenoble, France

Received: 12 June 2007
Accepted: 6 July 2007

Abstract

We studied structural changes in C₆₀ and C₇₀ peapods —i.e. C₆₀ and C₇₀ chains inserted inside single-walled carbon nanotubes— when submitted to high pressure and temperature conditions. X-ray diffraction experiments showed that while C₆₀ molecules polymerize inside nanotubes at pressures and temperatures consistent with polymerization in bulk C₆₀ phases, no polymerization is observed in C₇₀ peapods, even at pressures and temperatures above the threshold for polymerization in bulk C₇₀. 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 confinement on the behaviour of C₇₀.