Chemistry Reference
In-Depth Information
Fig. 6 Structural classification of the different families of C
60
-polymers
Analogously, heterometallic polymers, a family of heteroatom-containing
polymers, in which elements other than carbon are present in their structures, are
obtained by means of charge-transfer polymerization mediated by metals [
76
] and
also by electro-reduction in the case of fullerene epoxide [
77
,
78
].
Another family of polyfullerenes that needs little chemical control is the cross-
linked set. Their synthesis usually proceeds from tridimensional random and quick
reactions involving several of the 30 equivalent double bonds of the fullerene cage.
Nevertheless, some control over the addition reactions is required in order to avoid
a dramatic intractability of the final products. Different synthetic strategies have
been followed till now for their preparation including the reaction between fuller-
ene (or a C
60
-derivative) and a monomer or with the pending groups (or the end
termini) of preformed polymers.
On the other hand, the incorporation of one or two fullerene units at the terminal
positions of linear polymeric chains leads to the end-capped C
60
-polymers. It is
worth noting that the presence of C
60
moieties strongly influences both the molec-
ular and the bulk behavior of the parent polymers as a result of the modification of
their hydrophobicity. Two different synthetic strategies have been employed to
prepare this class of polymers: the capping of a polymer chain with C
60
or the
growth of a polymeric backbone from the surface of a fullerene moiety or a C
60
-
derivative, the so called “
graft to
” and “
graft from
” approaches. These protocols
can also be easily used in the synthesis of the members of the star-shaped polymers,
which are constituted by 2-12 long and flexible polymer chains covalently linked to
a fullerene cage with topologies similar to that of sea-stars.
