Polystyrene-attached graphene oxide with different graft densities via reversible addition-fragmentation chain transfer polymerization and grafting through approach

Abstract

Graphene oxide (GO) modified with double bond was utilized in grafting polystyrene chains to its surface through reversible addition-fragmentation chain transfer (RAFT) polymerization of styrene. For this purpose, 3-(((2-aminoethyl)amino)dimethylsilyl)propyl methacrylate (OD) including double bond and amine groups was prepared and used for modification of GO in different grafting densities by a ring-opening nucleophilic reaction. Then, polystyrene-grafted GO was obtained by “grafting through” RAFT polymerization of styrene. Successful using of RAFT polymerization, efficiency of the grafting reaction, different characteristics of the graphene-attached and free polystyrene chains were investigated. Proton nuclear magnetic resonance spectroscopy confirmed successful synthesis of OD. Its grafting on GO was also confirmed by using X-ray photoelectron spectroscopy. The neat and modified GO layers were also investigated by Fourier transform infrared and Raman spectroscopies. Size exclusion chromatography was used to study molecular weight and polydispersity index of the attached polystyrene chains. Thermogravimetric analysis provides degradation temperature, char content, and grafting ratio of the modifier and polystyrene chains. Grafting ratio of OD was 10.3 and 4.4% for the modified GO layers with high and low grafting densities, respectively. Layers morphology was visually studied by scanning and transmission electron microscopies. Flat and smooth graphite platelets were changed to wrinkled layers after oxidation, and converted to opaque layers after grafting with polystyrene chains. High length of small molecule modifier in this study resulted in highly efficient grafting reaction.