ABSTRACT
The intrinsic efficiency of fullerenes can be significantly activated by means of a connection with hydrogen donating groups of antioxidants such as phenol or secondary amine The developed system of conjugated s–p bonds arranged in the fullerene molecule in a closed shape can promote a strong resonance effect on the grafted units and increase the hydrogen atom abstraction efficiency. In this case the known ability of fullerene to trap alkyl radicals might be combined with an additional antioxidant functionality to afford a new class of antioxidants with bimodal action. Explorations in the field of fullerene derivatives on their antioxidant performance provide novel information on the potential stabilization properties of this type of molecular structure.
This chapter describes an anti-oxidative influence of fullerene-alkyl pyrrolidines on the model hydrocarbon and polymer oxidation environment. The antioxidant activity of the investigated derivatives was studied by measuring the inhibition rate constants for their reaction with alkyl and peroxy radicals in a model cumene initiated (2,2′-azobisisobutyronitrile, AIBN) oxidation experiments and compared to that recorded under identical experiments for buckminsterfullerene itself and commercial stabilizers.
The results indicate that linking the alkyl pyrrolidine groups directly to the fullerene core gives rise to an additional antioxidative power to the buckminsterfullerene:–they heighten the inherent rate constant of buck-minsterfullerene for scavenging alkyl radicals due to the additional antioxidant contribution promoted by the radical-quenching ability of the formed nitroxyl intermediates.
This novel C60-amine conjugates may be considered as promising molecules for broad-spectrum radical scavenging antioxidants to use purposely in polymer materials, in particular in low-density polyethylene (LDPE) composite formulations.
