Controlled grafting of polymer chains onto C60 and thermal stability of the obtained materials

‘Model’ polymer stars with a fullerene core and arms of defined molar masses and low polydispersities can be prepared by grafting ‘living’ anionic polymers or macro-radicals onto C60. The specific chemical reactivity of C60 leads in both cases to a peculiar addition mechanism that allows to perfectly control the number of arms between 2 and 6. Upon addition of ‘living’ polymers, the carbanions generated on C60 are delocalized on a single conjugated molecule, and the observed upper limit of six grafts results from this specific situation. It is also possible to take advantage of the increase of reactivity of the carbanionic sites located on the fullerene with their number to produce more sophisticated architectures such as ‘palm-trees’ or ‘dumbbells’. Upon heating (PS)xC60 in solution the arms are released showing that the covalent bond between the fullerene and the polymer chains breaks first. The presence of this ‘weak’ bond is responsible for the decreased thermal stability of these compounds as compared to polystyrene. The reduced stability of any direct bond to C60 seems general as the addition onto C60 of only even number of macro-radicals generated through an atom transfer reaction results also from the lower stability of C60–Br as compared to PS–Br. The presence of grafted polymer chains on the C60 allows organizing this fullerene at the nanoscale in a polymer matrix using the well known self-assembling of block copolymers. To cite this article: C. Mathis et al., C. R. Chimie 9 (2006).