Highly ordered mesoporous silica (MPS) and sulfonated mesoporous organosilicate (s-MPOs) were synthesized as novel inorganic additives derived for use in PEM-FCs, and were added to the non-protonic polymer matrix, poly(ethylene-co-vinyl alcohol) (EVOH). The proton conductivities of EVOH composites were measured at 50-100 degrees C under controlled high humidity values. The EVOH27 (ethylene content: 27 mol%) composite membranes filled with s-MPOs gave a proton conductivity more than 50-times higher than composites filled with simple treated MPS (t-MPS). The s-MPOs having many SO3H groups was able to form effective proton conductive passages via its periodic structure and so improve conductivity in the polymer. We also investigated the temperature dependence of the conductivity for EVOH composites with ethylene content 01 27 and 44 mol%. The EVOH44/s-MPOs composites had better conductivity than EVOH27 at higher temperatures. The greatest value was estimated to be 1.67 x 10(-3) S cm(-1) without extra acid additives, at 80 degrees C and more than 96% RH. (C) 2011 Elsevier B.V. All rights reserved.