Novel Crosslinker for Photopolymerization of Proton Conducting Fuel Cell Membranes

Abstract

Direct methanol fuel cells with polymer electrolyte membranes are of great interest in recent research. Several monomers and crosslinkers in a broad range of concentrations in water and NMP respectively were screened for their mechanical properties, water uptake and conductivity by photopolymerization with a polar photo initiator in porous membranes made of polypropylene and polyethersulfone, respectively. As conductive ionomer, primarily AMPS, an acrylamide with a sulfonic end group, was used. The conductive monomers were crosslinked with varying hydrophobic and hydrophilic multifunctional monomers based on (meth-) acrylates. Furthermore several new multifunctional crosslinkers based on acrylamides with enhanced thermal and ageing stability have been synthesized and tested.

The advantage of several different building blocks with known characteristics is the possibility to tune the polymer to special needs of an application. For example, some polymer compositions have good conductivity at lower temperatures, whereas other polymers develop better properties at elevated temperatures. By choosing the right building blocks we were able to achieve better proton conductivity than Nafion.