Abstract: In a method for preparing a membrane to be assembled in a membrane electrode assembly, such as a polymer electrolyte membrane fuel cell, a base polymer film is irradiated with at least one of electromagnetic and particle radiation in order to form reactive centers within the polymer film. The irradiated film is exposed to a mixture of monomers amenable to radical polymerization to form a graft copolymer in the irradiated film. The mixture includes ?-methylstyrene and methacrylonitrile. The grafted film is sulfonated to introduce sulfonic acid sites providing ionic conductivity of the material.

Abstract: According to the present invention a method for grafting a chemical compound to a predetermined region of a support substrate (4) is disclosed, comprising: a) irradiating selectively the support substrate with electromagnetic radiation and/or particle radiation in order to both define said predetermined region and to form at least one reactive functional group or a precursor thereof in said predetermined region of the support substrate; b) exposing the irradiated support substrate to said chemical compound or to a precursor thereof. Therefore, only these very few steps are needed to effectively grafting the desired chemical compound, such as an organic compound, to the predetermined regions of the support substrate. Moreover, the irradiation step can be carried out in a vastly flexible manner and allows to generate numerous distinct shapes of the predetermined regions.