New nanostructured materials based on fullerene and biodegradable polyesters

Star-shaped poly(epsilon-caprolactone) (PCL) with a fullerene (C-60) core, C-60[N(CH2)(12)OPCLOH](x), was successfully synthesized by reaction of azide-terminated PCL with C-60. Both the experimental conditions and the stoichiometry were optimized, such that an average of six PCL chains was grafted per fullerene core. The molecular weight of the polyester chains directly controlled the length of the arms of the star-shaped polymers. Singlet oxygen was generated on irradiation of the C-60[N(CH2)(12)OPCLOH] x nanohybrids. These C-60[N(CH2)(12)OPCLOH](x) nanohybrids were then processed in two kinds of nanomaterials. First, they were encapsulated within the core of micelles formed by biocompatible amphiphilic block copolymers. In water, the particle size distribution of these nanoparticles was narrow, and their diameter was in the range of 100 to 200 nm. Second, C-60-containing micro-/nanosized polymer fibers were prepared, for the first time, by electrospinning. The average diameter of the fibers was varied by tuning the PCL/C-60[N(CH2)(12)OPCLOH](x) weight ratio. Grafting of polyester chains onto C-60 is thus a suitable strategy for producing easily processable C-60 and attractive building blocks for incorporation of C-60 in nanomaterials.