Benzimidazole effect on the performance of polyelectrolyte membranes based on sulfonated hydrocarbon resin

Resumo

It is well known that polybenzimidazole electrolyte membranes do not have water dependence as nafion® membrane and it could be used at intermediate and higher temperatures (T>100ºC). Otherwise benzimidazole groups can act promoting próton conduction in sulphonated membrane improving the polyelectrolyte efficiency. This paper discusses an alternatively use of heterocycles (benzimidazole and a derivative benzimidazole) as protogenic groups for sulfonated hydrocarbon resins (SR) and poly(vinyl alcohol) semi-interpenetrated polymer network (SR/PVA) operating at low temperatures. The PVA, a water soluble polymer, was reticulated with glutaraldehyde and the membranes modified with benzimidazole compounds were prepared by casting technique from water solution. The SR/PVA membranes were characterized by water uptake measurements, FTIR spectroscopy, thermogravimetric analysis (TGA) and the conductivity were assessed by impedance spectroscopy. The presence of benzimidazole leads to moderate water uptake and this increased with increasing the heterocycles content and the sulfonic acid functionalized membrane showed reasonable properties. The polyelectrolyte membranes with 40 and 50% (wt%) of benzimidazole showed the highest conductivity values and the 1,4- Bis(N benzimidazolyl) butane reduced the membrane conductivity.