Grafting of polymers onto graphene oxide by trapping of polymer radicals and ligand-exchange reaction of polymers bearing ferrocene moieties

It was found that graphene oxide (GO) acts as a strong radical scavenger and undergoes a ligand-exchange reaction with ferrocene. Then, the grafting of polymers onto GO was examined by two processes: (1) trapping of polymer radicals by GO and (2) ligand-exchange reaction of polycondensed aromatic rings of GO with ferrocene moieties of a copolymer. It was found that poly(ethylene glycol) (PEG) radicals formed by thermal decomposition of Azo-PEG, which contains thermally decomposable azo linkage in the main chain, were successfully trapped by GO to give PEG-grafted GO: the percentage of PEG grafting was determined to be 15.4%. On the other hand, by heating of GO with copolymers containing vinyl ferrocene (Vf) moieties, such as poly(Vf-co-methyl methacrylate) and poly(Vf-co-styrene), in the presence of AlCl3 and Al powder as catalyst, the corresponding copolymer was grafted onto the GO based on the ligand-exchange reaction of ferrocene moieties of these copolymers with polycondensed aromatic rings of GO: the percentage of grafting of poly(Vf-co-methyl methacrylate) onto GO reached to 54.2%. The grafting of these polymers onto the GO surface was confirmed by XRD and thermal decomposition GC-MS. PEG-grafted and poly(Vf-co-MMA)-grafted GO gave a stable dispersion in organic solvents of grafted polymer.