ELECTROCHEMICAL IMPEDANCE STUDIES OF HYBRIDS OF PERFLUOROSULFONIC ACID IONOMER AND SILICON-OXIDE BY SOL-GEL REACTION FROM SOLUTION

Hybrids of Nafion (R) and silica were prepared from solution, growing the inorganic phase by hydrolysis/condensation of alkoxy silanes. Usin g tetraethoxysilane (TEOS) as the inorganic precursor, transparent and rigid films were obtained. Substituting part of the TEOS (20 wt% subs titution) by 1,1,3,3 tetramethyl-1,3-diethoxydisiloxane (TMDES) more f lexible films were obtained. These films were translucent and showed a phase segregation which was clearly observed by transmission electron microscopy. The ionic conductivity of the hybrids was measured by ele ctrochemical impedance spectroscopy using two stainless steel electrod es, a frequency range of 0.1 to 10(5) Hz, and temperatures from 25 to 100 degrees C. Samples were also characterized by modulated differenti al scanning calorimetry. (C) 1998 Elsevier Science S.A. All rights res erved.