The mechanism of addition of various “living” anionic polymers
on C60 has been investigated
in apolar and polar solvents, and well-defined star-shaped
macromolecules with a C60 core have been
prepared. In toluene, only addition of the carbanions onto double
bonds on the fullerene is observed.
The maximum number of grafted chains depends on the reactivity of
the carbanion borne by the chain;
this value is six for the very reactive “living” polystyrene and
polyisoprene but only three using the more
stable diphenylalkyl carbanion. The number of grafts can be, to
some extent (3−6), controlled by
stoichiometry. In THF, the reaction mechanism is more
complicated: 2 electrons are first transferred
from the carbanions to the fullerene producing the C60
dianion and then addition takes place. The number
of grafted chains depends not only on the reactivity of the carbanion
but also on its “bulkiness”: four
chains are grafted with the carbanion styryl, three with
2-vinylpyridyl, and none using diphenylethyl.
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