Thermally and chemically stable proton conductors were prepared via surface-sulfonation of sol-gel-derived phenylsilsesquioxane-methylsilsesquioxane (PhSiO3/2-MeSiO3/2) particles in a range from 250 to 650 nm in diameter. MeSiO3/2 component was indispensable to improve the chemical durability against sulfonation solvent. Proton conductivity of the pelletized samples prepared using the sulfonated PhSiO3/2-MeSiO3/2 particles increased linearly with increasing the ion exchange capacity (IEC) of the particles. The mobility (mu) of proton was calculated to be 0.3 x 10(-4) cm(2)/V s. Porous PhSiO3/2-MeSiO3/2 particles prepared using a cationic surfactant of cetyltrimethylammonium bromide (CTAB) as a template of pores showed higher both IEC and water uptake, leading to an increase in proton conductivity to similar to 10(-2) S/cm at 80 degrees C and 80% relative humidity. (C) 2007 Elsevier B.V. All rights reserved.