Preparation and characterization of novel grafted cellophane-phosphoric acid-doped membranes for proton exchange membrane fuel-cell applications

This work concerns preparation of acid-base polyelectrolyte membranes for fuel-cell applications from cellulosic backbones for the first time. Grafted cellophane-phosphoric acid-doped membranes for direct oxidation methanol fuel cells (DMFC) were prepared following three steps. The first two steps were conducted to have the basic polymers. The first step was introducing of epoxy groups to its chemical structure through grafting process with poly(glycidylmethacrylate) (PGMA). The second step was converting the introduced epoxy groups to imides groups followed by phosphoric acid (-PO3H) doping as the last step. This step significantly contributes to induce ion exchange capacity (IEC) and ionic conductivity (IC). Chemical changes of the cellophane composition and morphology characters were followed using FTIR, TGA, and SEM analysis. Different factors affecting the membranes characters especially IEC, methanol permeability, and thermal stability were investigated and optimized to have the best preparation conditions. Compared to Nafion 117 membrane, cellophane-modified membranes show a better IEC, less methanol permeability, and better mechanical and thermal stability. IEC in the range of 12.3 meq/g compared to 0.9 meq/g per Nafion was obtained, and methanol permeability has been reduced by one-order magnitude. However, the maximum obtained IC for cellophane-PGMA-grafted membrane doped with phosphoric acid was found 2.33 x 10(-3) (S cm(-1)) compared to 3.88 x 10(-2) (S cm(-1)) for Nafion 117. The obtained results are very promising for conducting further investigations taking into consideration the very low price of cellophane compared to Nafion. (C) 2011 Wiley Periodicals, Inc. J Appl Polym Sci 123: 3710-3724, 2012