Fullerene polymers:: Synthesis and properties

The different synthetic strategies to prepare fullerene-containing polymers, either covalently or supramolecularly connected, have been reviewed. Implementing the chemistry of fullerenes into macromolecular chemistry has allowed the preparation of new polymer materials exhibiting outstanding structural, electrochemical, and photophysical properties that might find application, and in some cases are currently under intensive and competitive research, in different fields. The different C60-based polymers have been classified according to structural parameters, and consequently, those polymers bearing one or two C60 units at the ends or as the core of the polymer chain have been discussed separately since the presence of the fullerene moieties produce significant modification of the former polymer. Polymers bearing C60 units covalently attached have been presented as crosslinked, main-chain, and side-chain polymers whose preparation has involved a wide variety of synthetic strategies. All-C60 and related polymers are a singular class of polymers which have undergone rapid progress from starting work reporting poorly characterized materials to more recent examples involving well-defined synthetic strategies. The so-called "double-cable" approach is an elegant and realistic concept for the preparation of photo- and electroactive polymers for photovoltaic applications which has received a lot of attention during the last years. It represents a rational approach to control structural and electronic parameters in the design of photovoltaic devices in which the morphological aspects play a leading role. It is important to note, however, that this approach has not yet fulfilled the initial expectations, and more work is needed for a better understanding of the key aspects in the fabrication of organic solarcells. Supramolecular chemistry of fullerenes is a very recent field which has been scarcely studied in assemblies involving macromolecules. The few and significant examples known so far have been discussed and classified according to the different synthetic strategies followed for the assemblies preparation. H bonding, electrostatic interactions, and π-π interactions have been mainly used for the preparation of these new photo- and electroactive supramolecular architectures. This is living interdisciplinary research in which new approaches can be developed with the only limitation being the imagination of the chemists. As a representative example, new fullerene-polyyne nanospheres via thermally induced solid-state polymerization have recently been reported, leading to the first preparation of evenly distributed and uniform-sized C60-based nanospheres. In contrast to previous reports on fullerene nanoaggregates, a remarkable feature in this case is formation of orderly structured nanosphere arrays from amorphous solid thin films, thus opening a new way to different carbon nanostructures. In summary, we are at the dawn of a new interdisciplinary field in which C60-based polymers should furnish unprecedented materials in which the integration of fullerenes as a photo- and electroactive building blocks into the polymer structure should result in new properties for development of realistic applications. In this regard, 20 years after the discovery of fullerenes, the scientific community is looking for real applications of the new carbon allotropes. Once more, the ease processability and availability of polymers could be the key for application of fullerenes for practical purposes. © 2006 American Chemical Society.