A range of mono- and bis-functionalised fullerenes have been synthesised and inserted into singlewalled
carbon nanotubes. The effect of the size and shape of the functional groups of the fullerenes on
the resultant 1D arrays formed within the nanotubes was investigated by high resolution transmission
electron microscopy and X-ray diffraction. The addition of non-planar, sterically bulky chains to the
fullerene cage results in highly ordered 1D structures in which the fullerenes are evenly spaced along the
internal nanotube cavity. Theoretical calculations reveal that the functional groups interact with
neighbouring fullerene cages to space the fullerenes evenly within the confines of the nanotube. The
addition of two functional groups to opposite sides of the fullerene cages results in a further increase in
the separation of the fullerene cages within the nanotubes at the cost of lower nanotube filling rates.
