Effect of interface modification on PMMA/graphene nanocomposites

Graphene platelets (GnPs) were surface modified with a long-chain surfactant B200, and then compounded with polymethyl methacrylate (PMMA). B200 provided an anchor into GnPs and a bridge into the matrix, thus creating molecular entanglement between matrix and GnPs. The interface modification promoted the dispersion of GnPs, as no aggregates of GnPs were observed on the fracture surface of the modified composites, in sharp contrast with the unmodified composites. Although GnPs formed clusters in the matrix, bilayer graphene was readily observed under TEM in randomly selected regions; it showed high structural integrity under diffraction pattern. The addition of 2.7 vol% m-GnPs produced 32.8 % improvement in the flexural modulus of PMMA as compared to 9.0 % by unmodified GnPs. At 1.1 vol%, the interface-modified composite showed a 19.6 % improvement in the absorption resistance to ethanol, in comparison with 3.8 % for the unmodified composites. The addition of 2.7 vol% m-GnPs improved fracture toughness of PMMA by 79.2 %, while GnPs enhanced it by 23.9 %.