High temperature protonic conducting polymer membranes provide new technological applications in electrochemical devices including electrochromic displays, chemical sensors, fuel cells and others. Organic/inorganic nanocomposite membranes consisting of SiO2/PEO (polyethylene oxides) hybrids are a remarkable family of isotropic, flexible, amorphous polymer materials, which have been synthesized through sol-gel processes. The hybrid membrane doped with acidic moieties such as monododecylphosphate or phosphotungstic acid shows good protonic conductivities at high temperatures above 100 degrees C. The protonic conducting membrane was found to be thermally stable at high temperatures because of the inorganic SiO2 framework in the nanocomposite matrix.