Novel polyethersulfone compositions have been discovered which incorporate structural subunits derived from sulfonated bis(halophenyl)sulfones, dihydroxy terphenyls, and/or bis(hydroxyphenyl)pyridines. The sulfonated polyethersulfones show promise as materials for use in polymer electrolyte membranes (PEMs) in fuel cells owing to their high proton conductivities (0.02-0.07 S/cm at 20.degree. C. and 100 percent humidity). In addition, a novel unsulfonated thermoplastic polyethersulfone comprising structural subunits derived from a non-sulfonated bis(halophenyl)sulfone bis4-fluorophenyl)sulfone and 4,4'-dihydroxyphenyl-2,6-pyridine (CAS No. 171820-16-9) is disclosed.