Grafting via Radicals

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. 

1 Radical Copolymerization of Fullerenes with Vinyi Monomers 

I = initiator, R = primary radical, RM/ = growing polymer chains. For a complete reaction scheme see Reference [15]. 

To prepare star-shaped macromolecules with a well-defined number of arms of about the same length it is necessary to separate the polymerization step from the addition onto the fullerene. This can be done using controlled radical polymerization or macro-initiators. 

This type of chemistry towards well-defined star-shaped (polymer)j,Qo is closely linked to progress made during this last decade in radical polymerization [3]. Indeed, the various controlled radical polymerizations such as nitroxide-mediated polymerization (NMP) or atom transfer radical polymerization (ATRP) allow us to produce polymer chains with tailored chain length and low polydisper-sities. Furthermore, the as-prepared chains bear at their end a function (stable radical or C—halogen bond) that can be converted under the right conditions into a macro-radical. If this latter is produced in the presence of Cgo, several chains should add to the fullerene. 

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