The development of alternative, non-fluorinated membranes for polymer electrolyte membrane fuel cellsnecessitates the co-development of a non-fluorinated electrode catalyst binder to ensure compatibility betweenmembrane and electrode. However, most hydrocarbon based polymers have lower gas permeability than perfluorinatedNafion. In this work we tried to obtain a sulfonated, non-fluorinated binder based on PIM-1 (polymer of intrinsicmicroporosity 1) which has up to 2000 times higher permeability than Nafion. However, sulfonation was notstraightforward and often led to degradative side reactions. Sulfonated polymers were too brittle to give stable membranesand the highest experimental IEC was 1.03 meq/g, significantly lower than the theoretical IEC of 3.2 meq/g(2 sulfonic acid groups per repeat unit).