Effect of microstructure on the antioxidant properties of fullerenepolymer solutions

Abstract

Fullerene (C₆₀) is known for its strong radical scavenging properties. Its applications in aqueous environments can be enhanced by grafting hydrophilic polymers to fullerenes. The radical scavenging kinetics of four water-soluble fullerene polymeric systems (C₆₀-PAA-C₆₀, PAA-C₆₀, PEO-b-PAA-C₆₀ and PDMA-C₆₀) were characterized using the 1,1-diphenyl-picryl-hydrazyl (DPPH) colorimetric assay. The radical scavenging process displayed a 2-stage kinetic trend, which correlates to the self-assembly behaviour of fullerene-polymer systems in aqueous solutions. Since a mixture of unimers and micelles exists, the first kinetic process is attributed to the scavenging property of the more accessible unimers, while the second stage corresponds to the scavenging behaviour of micelles. The rate of the micellar scavenging reaction is determined by the size of the micelle: the larger the micelle, the faster the reaction, as there is a larger number of fullerenes available for the scavenging reaction. These findings demonstrate the effect of nanostructure on the antioxidant efficiency of fullerene polymer solutions. Such knowledge will facilitate the design of optimally efficient radical scavenging fullerene-polymer systems.