Comb-shaped poly(arylene ether sulfone)s as proton exchange membranes

A new sulfonated side-chain grafting unit containing two or four sulfonic acid groups was synthesized using sulfonated 4-fluorobenzophenone (FBP) and 1,1-bis(4-hydroxyphenyl)-1,4-((4-fluorophenyl)thio)phenyl-2,2,2-trifluoroethane (3FBPT). A conventional aromatic nucleophilic substitution (SNAr) was used for copolymerization of poly(arylene ether sulfone) containing a methoxy group. After converting the methoxy group to the reactive hydroxyl group, this functionalized copolymer was reacted to graft the sulfonated side chains to make the comb-shaped sulfonated poly(arylene ether sulfone) copolymers. All the polymers were characterized by H-1 NMR, thermogravimetric analysis (TGA), the water Uptake, and proton and methanol transport for fuel cell applications. These comb-shaped sulfonated polymers had good properties as polyelectrolyte membrane materials. The comb-shaped copolymers with two or four sulfonic acid groups show high proton conductivity in the range of 34-147 and 63-125 mS/cm, respectively. The methanol permeabilities of these copolymers were in the range of 8.2 x 10(-7) -5.6 x 10(-8) cm(2)/s. A combination of high proton conductivities, low water uptake, and low methanol permeabilities for some of the comb-shaped copolymers indicated that they are good candidate materials for proton exchange membrane in fuel cell applications.