New polymer electrolytes consisting of diphenyl sulfone units with –O–(CH2)3SO3M (M = H or Na) side chains have been prepared. Dehalogenative polycondensation using a zero-valent nickel complex, [Ni(0)Lm], gave a homopolymer, Polymer-1(Na), from Cl–Ph(R)–SO2–Ph(R)–Cl (monomer-1; Ph(R) = 1,3-phenylene unit having the –O–(CH2)3SO3Na side group at the 4-position). Protonolysis of Polymer-1(Na) gave Polymer-1(H) with a weight average molecular weight of 25,000. Polymer-2(H) was synthesized by Suzuki-Miyaura cross coupling of Br–Ph(R)–SO2–Ph(R)–Br (monomer-2) and C6H4(B(OH)2)2-p using [Pd(PPh3)4] and ensuing protonolysis. Crosslinking of Polymer-2(H) with 1,4-benzenedimethanol gave a water-protected film. The cross-linked film of Polymer-2(H) showed proton conductivity of 0.26 S cm−1 at 80 °C and 90% humidity.