KAGAKU KOGAKU RONBUNSHU, Vol.29, No.2, 159-164, 2003
Development of pore-filling type polymer electrolyte membrane made by plasma graft polymerization with PTFE substrate
For direct methanol fuel cell (DMFC) application, a new type of electrolyte membrane was developed. We are proposing a pore-filling type electrolyte membrane for the application. Pores of porous substrate are filled with polyelectrolyte polymer. The filling polymer exhibits proton conductance and porous matrix suppress the filling polymer swelling to reduce methanol crossover and also provide mechanical strength at high temperature. The pore-filling electrolyte membrane was made by plasma graft-filling polymerization. Poly (tetrafluoroethylene) (PTFE) was employed as the substrate and poly (acrylic acid) or poly (acrylic acid-co-allylsulfonate) was used as the filling grafted polymer. Using plasma power 30 W, pores of PTFE substrate was homogeneously filled with the grafted polymer, and the pore-filling type polyelectrolyte membrane was developed. For poly (acrylic acid-co-allylsulfonate) grafted polymer cases, grafting rate and allylsulfonate content were enhanced by adding salt to the monomer solution. This may be due to reduction of double charge layer thickness of sulfonic group, and the effect can enhance the reactivity of allylsulfonate. The membranes contains sulfonic group of 0.48 mmol/g-membrane.