Sulfonated block copolymers that may be used as membranes for
fuel cells include sulfonated
polyaryletherketone blocks and lightly sulfonated polyethersulfone blocks. The sulfonated
polyaryletherketone blocks include structural units of formula and the lightly sulfonated polyethersulfone blocks include structural units of formula wherein R1, R2, R3, R4, R5 and R6 are independently C1-C10
alkyl, C3-C12 cycloalkyl, C6-C14
aryl, allyl, alkenyl, alkoxy, halo, or cyano; Z, Z1 and Z2 are independently a direct bond or O, S, (CH2)r, (CF2)r, C(CH3)2, C(CF3)2, or a combination thereof; M is H, a
metal cation, a non-metallic inorganic cation, an organic cation or a mixture thereof; a and e are independently 0 or an integer from 1 to 3; b, c, d, and f are independently 0 or an integer from 1 to 4; m, n and p are independently 0 or 1; and r is an integer from 1 to 5.