Hydroxide exchange membrane (HEM) is the most important and key performance-limiting component of HEMFC. Plasma copolymerization is adopted to synthesize the hydroxide exchange membranes with microphase-separated structure. The X-ray photoelectron spectroscopy and Fourier transform infrared spectroscopy demonstrate that the quaternary ammonium groups can be successfully introduced into the polymer matrix in the plasma copolymerization process. The transmission electron microscope images reveal that plasma copolymerization allowed the generation and aggregation of ionic groups and the formation of ionic transport channels, leading to an excellent phase-separated morphology of the membrane. The plasma-copolymerized hydroxide exchange membranes possess excellent hydroxide ion conductivity, chemical and thermal stability, ultra-thin and mechanical integrity structure, as well as the ability of building an efficient three-phase-boundary, making them very exiting candidates for fuel cell applications. (C) 2011 Elsevier B.V. All rights reserved.