Facile Functionalization of Multilayer Fullerenes (Carbon Nano‐Onions) by Nitrene Chemistry and “Grafting from” Strategy

Facile functionalization of multilayer fullerenes (carbon nano- onions, CNOs) was carried out by (2 + 1) cycloaddition of nitrenes. The prod- ucts were further derivatized by using the "grafting from" strategy of in situ ring-opening polymerization (ROP) and atom transfer radical polymeri- zation (ATRP). Using one-step nitrene chemistry with high-energy reagents, such as azidoethanol and azidoethyl 2- bromo-2-methyl propanoate, in N- methyl-2-pyrrolidone at 1608C for 16 h, hydroxyl and bromide functionalities were introduced onto the surfaces of CNOs. These hydroxyl CNOs (CNO- OH) and bromic CNOs (CNO-Br) were extensively characterized by vari- ous techniques such as thermal gravi- metric analysis (TGA), transmission electron microscopy (TEM), Raman spectroscopy and X-ray photo electron spectroscopy (XPS). TGA measure- ments indicated that the surface hy- droxyl and bromide group density reached 1.49 and 0.49 mmol g 1 , respec- tively. The as-functionalized CNOs showed much better solubility in sol- vents than pristine CNOs. The CNO- OH were also observed to fluoresce at l = 453 nm in water. The CNO-OH and CNO-Br can be conveniently utilized as macroinitiators to conduct surface- initiated in-situ polymerizations. Poly(e-caprolactone) (PCL, 45wt %) and polystyrene (PS, 60 wt%) were then grafted from surfaces of CNOs through the ROP of e-caprolactone with the macroinitiator CNO-OH and the ATRP of styrene with the macro- A CNO-Br, respectively. The structures and morphology of the re- sulting products were characterized by 1 H NMR, scanning electron microsA (SEM), TEM, and atomic force micros- copy (AFM). The polymer functional- ized CNOs have good solubility/disper- sibility in common organic solvents. The facile and scalable functionaliza- tion approaches can pave the way for the comprehensive investigation of chemistry of CNOs and fabrication of novel CNO-based nanomaterials and nanodevices.