Polyacrylonitrile (PAN)-based composite membranes were prepared by immersion precipitation method by using poly(N,N-dimethylaminoethyl methacrylate)-grafted silica (PDMAEMA@SiO2) nanoparticles as hydrophilic additives. The molecular weight of PDMAEMA were controlled by the surface initiated atom transfer radical polymerization of N,N-dimethylaminoethyl methacrylate on SiO2 nanoparticles. The synthesized nanoparticles have a typical core-shell structure as characterized in detail by FT-IR, TEM, DLS and GPC. The prepared PAN-based composite membranes have higher porosity and water permeation flux than those of the pure PAN membranes. They also show high rejection (>= 90%) to bovine serum albumin and high flux recovery ratio (>= 90%) to water permeation. These improved performances are attributed to the good hydrophilicity of PDMAEMA@SiO2 nanoparticles. The results suggest that PDMAEMA@SiO2 nanoparticles are suitable for the property optimization of PAN-based composite membranes. (C) 2014 Elsevier B.V. All rights reserved.