Tunable positive temperature coefficient of resistivity in an electrically conducting polymer/graphene composite

The graphene nanosheet (GNS)/ultrahigh molecular weight polyethylene composite with a two-dimensional conductive network of GNSs exhibits an increasing positive temperature coefficient (PTC)of resistivity while thermally treated at a certain temperature. This anomalous phenomenon is originated from the reduced viscosity of polymer matrix, crystallization induced local flow and weak interactions among the overlapping joints of GNSs, which allow GNSs to migrate to the polymer matrix, thus weakening the conductive paths and increasing the PTC intensity. A facile approach is accordingly developed to prepare a conductive polymer composite with a tunable PTC intensity. The authors gratefully acknowledge the financial support by the National Outstanding Youth Foundation of China (Grant No. 50925311). Thanks are also given to Zhu Li from Analytical and Testing Center of Sichuan University for his help in the SEM measurements