Optimizing the free radical content of graphene oxide by controlling its reduction

Radicals can form at the edges and defect sites on graphene plane. However, the radical content of graphene is too low to be practically useful. This study demonstrates how the radical content of graphene can be enhanced and optimized simply by oxidation and reduction treatments. Graphene oxide nanosheets are produced by oxidation of graphite and different reduction methods including thermal, chemical and photo reduction are used to obtain different degrees of reduction and free radical formation on the nanosheets. The reactivity and usefulness of the radicals are demonstrated for surface and bulk polymerization of butyl acrylate. Compared to a conventional initiator, ammonium persulfate, although the polymerization kinetics is slower when graphene radicals are used, a higher polymerization yield can be achieved. Moreover, the higher stability of graphene radicals helps to avoid the radical-induced polymerization termination, a common problem that limits the efficiency of conventional radical initiators.