NOVELTY - Providing an ion exchange polymer membrane that selectively separates methanol while passing water and protons, in which the diffusion of methanol is effectively prevented by a barrier material to inhibit the transmission of methanol on the surface or interior of a polymer membrane.    USE - For fuel cell (claimed) as separator e.g. direct methanol fuel cell using methanol and water mixture as fuel.    ADVANTAGE - The ion-exchange membrane exhibits low methanol crossover and high proton conductivity and is thus suitable for use in direct methanol fuel cells, economically. The membrane selectively separates methanol while passing water and protons, in which the diffusion of methanol is effectively prevented by a barrier material to inhibit the transmission of methanol on the surface or interior of a polymer membrane. The membrane contributes to a significant reduction in methanol crossover, without decreasing its fundamental capability as an electrolyte membrane.    DETAILED DESCRIPTION - An ion-exchange membrane (10) comprises natural clay and/or modified organic clay (20), dispersed in ion- conducting polymeric film as a barrier material.    INDEPENDENT CLAIMS are included for the following:    (1) fabrication of ion-exchange membrane, which involves soaking to swell a prepared film membrane into a solvent, soaking the swollen film membrane into a suspension containing clay, and soaking the swollen membrane in an ion- conducting polymeric solution to form a self-assembly membrane;    (2) fuel cell equipped with an anode compartment having an anode, a cathode compartment having a cathode, and the ion-exchange composite membrane serving as a separator and electrolyte, positioned between the anode and cathode; and    (3) composite solution dispersing clay in an ion-conducting polymeric solution.    DESCRIPTION OF DRAWING(S) - The figure shows a schematic diagram of the structure of an ion-conducting composite membrane comprising a barrier material.    Ion-exchange membrane (10)    Natural clay and/or modified organic clay (20)