Star-Shaped Polymers with a Fullerene Core

Star-Shaped Polymers with a Fullerene Core 

Among the great diversity of fullerene-based macromolecular architectures [1] polymer-stars with a fullerene as the central core have been particularly well studied. Interest in them stems first from the potentialities of these new materials to combine the electronic properties of Ceo vvith the well-known advantages of polymers but also from the opportunities offered by the specific chemical reactivity of this fullerene to build new model star-shaped architectures. 

These multi-adducts can be prepared by three main synthetic strategies  

The fact that these multi-adducts may be obtained as mixtures of stereoisomers is not a drawback in material chemistry. Nevertheless, it has to be stressed that any addition imposes the opening of one of the thirty 6-6 bonds on the fullerene, which consequently induces a change in its electronic properties. To produce materials where the properties of the incorporated C ) are well defined, it is essential that the number of grafted chains (i.e., the number of opened double bonds) is perfectly controlled and is identical for all the fullerenes. Furthermore, as, for a given functionality x of the (polymer),C ) stars, the load of C o and the inter-fullerene distances will directly depend on the length of the grafted chains, it is also essential to be able to control the molar mass of the polymer and keep its polydispersity as low as possible. 

Fullerene Polymers. Synthesis, Properties and Applications. Edited by Nazario Martin and Francesco Giacalone Copyright 2009 WILEY-VCH Verlag GmbH Co. KGaA, Weinheim ISBN 978-3-527-32282-4 

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I 5 Star-Shaped Polymers with a Fullerene Core... 

The direct addition of an end-functionaUzed linear polymer chain onto a 6-6 bond on Ceo is the most commonly employed method to synthesize star-shaped polymers with a fullerene core. This grafting can occur via radicals, nucleophilic addition or insertion. 

Star-shaped macromolecules with a fullerene core combine in a single macromolecule the specific properties of fuUerenes with the well known advantages of polymers. Therefore, these materials may find applications in many fields (optical limiting, NLO, photovoltaics, plastic electronics, cancer therapy, etc). In addition, they can be prepared through a large variety of chemical routes. However, only a few allow for the preparation of pure adducts where a precise number of chains of a predetermined length and low polydispersity are grafted onto Qo- Such a control is necessary to obtain well-defined materials in which all the fullerene cores are in the same electronic state (i.e., the same number of opened double bonds) and the inter-fuUerene distances are adjustable. 

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