High temperature protonic conducting polymer membranes provide new technological applications in electrochemicaldevices including electrochromic displays, chemicalsensors and fuel cells. Organic/inorganimanocomposite membranes consisting of SiO2 /PEO (Polyethylene Oxides) hybrid 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 temperatures above 100°C. The protonic conducting membrane was found to be thermally stable at temperatures because of the inorganic SiO2 framework in the nanocomposites matrix.