Confined organization of fullerene units along high polymer chains

Conductive fullerene (C₆₀) units were designed to be arranged in one dimensional close contact by locally organizing them with covalent bonds in a spatially constrained manner. Combined molecular dynamics and quantum chemical calculations predicted that the intramolecular electronic interactions (i.e. charge transport) between the pendant C₆₀ units could be controlled by the length of the spacers linking the C₆₀ units and the polymer main chain. In this context, C₆₀ side-chain polymers with high relative degrees of polymerization up to 1220 and fullerene compositions up to 53% were synthesized by ruthenium catalyzed ring-opening metathesis polymerization of the corresponding norbornene-functionalized monomers. UV/vis absorption and photothermal deflection spectra corroborated the enhanced inter-fullerene interactions along the polymer chains. The electron mobility measured for the thin film field-effect transistor devices from the polymers was more than an order of magnitude higher than that from the monomers, as a result of the stronger electronic coupling between the adjacent fullerene units within the long polymer chains. This molecular design strategy represents a general approach to the enhancement of charge transport properties of organic materials via covalent bond-based organization.