Graphene nanosheets generated from sulfonated polystyrene/graphene nanocomposite

Recombination of graphene (GP) nanosheets into graphitic layer structure limits the large scale production of single layer GP and hence its applications. Sulfonated polystyrene (SPS)/GP composite consisting of ∼1 nm thick GP nanosheets was prepared by solution blending of exfoliated graphene oxide (GO) with SPS nanoparticles to address this issue. The presence of strong interactions such as hydrogen bonding and π-π interactions between the SPS and GO facilitated the formation of composite. During the reduction of GO to GP in the composite, GP sheets could not recombine into graphitic layer structure owing to the obstruction imposed by the SPS nanoparticles which were adsorbed on the GP sheets. The composites displayed higher moduli and ionic conductivities compared to pristine SPS. Significant mechanical reinforcement, for example 90% increase in storage modulus in case of 7% GP loading, by GP nanosheets enabled us to prepare mechanically strong SPS membrane which is otherwise brittle in nature. Composite exhibited higher proton conductivity compared to pristine SPS. In conclusion, a give-and-take approach was developed where SPS nanoparticles facilitated the formation of single layer GP nanosheets by blocking the recombination of these nanosheets into layer structure and in return GP nanosheets enabled the fabrication of mechanically stable ion conducting SPS membrane.