Melt mixing of nanoparticles with high performance polymers is not feasible due to severe shear heating and formation of particle aggregates. An alternative scheme was investigated in the present study involving the use of low molecular weight reactive solvents as processing aid and dispersings agent. Dispersion of nanosize fumed silica particles in polyethersulphone (PES) matrix was studied with the aid of small amounts of low molecular weight epoxy. Viscosity and processing temperatures of PES were significantly reduced and fumed silica particles were successfully dispersed to nanoscales. Epoxy component was polymerized after dispersion of fumed silica to recover the mechanical properties. Significant improvement in barrier resistance and heat deflection temperature over neat PES was observed.