Sulfonic-functionalized graphene oxide reinforced polyethersulfone nanocomposites with enhanced dielectric permittivity and EMI shielding effectiveness 

We have explored the sulfonic-functionalized graphene oxides (S-GOs) as an efficient conductive reinforcement to enhance the dielectric permittivity and electromagnetic interference (EMI) shielding effectiveness of the polyethersulfone (PES). The S-GOs having numerous terminal -SO3− groups not only promote the homogeneous dispersion for achieving the low percolation threshold, but also induce strong H-bonding and dipole–dipole interactions at the interfaces. As-prepared S-GO nanosheets showed uniform dispersion in PES matrix with strong adhesion with the polymer matrix via non-bonding interactions. The remarkable enhancement of dielectric permittivity of PES upon inclusion of S-GOs could be attributed to the interfacial polarization effect and microcapacitor model. As-prepared nanocomposites exhibited low conductive percolation threshold. The well-wrapped graphene nanosheets by thin PES layer prevented direct contact of graphene nanosheets and consequently decreased the dielectric loss by suppressing the current leakage. The PES/S-GO nanocomposites exhibited significant improvement in thermal stability with high char yield in N2 atmosphere compared to pure PES. A high EMI shielding effectiveness of 23.5 dB was achieved for the nanocomposite film with 5 wt% graphene loading, which might be originated from the development of conductive network at higher graphene loading. Overall, the as-prepared PES/S-GO hybrid nanocomposite could be used in DC and radiofrequency electronics.