Proton exchange membranes (PEMs) fabricated from sulfonated polyphenylenes (sPP) exhibit superior proton conductivity and electrochemical performance. However, the Ni(0) catalyst required for Colon's cross-coupling reaction for the synthesis of sPP block copolymers is expensive. Therefore, in this study, we generated Ni(0) in situ from an inexpensive Ni(II) salt in the presence of the reducing metal Zn and NaI. The sPP block copolymers were synthesized from neopentyl-protected 3,5- and 2,5-dichlorobenzenesulfonates and oligo(arylene ether ketone) using the catalyst NiBr2(PPh3)2. The block copolymers synthesized using our strategy and the Ni(0) catalyst exhibited comparable polydispersity index values and high molecular weights. Thin, transparent, and bendable PEMs fabricated using selected high-molecular-weight sPP block copolymers synthesized via our strategy exhibited similar proton conductivities to those of the block copolymers synthesized using the Ni(0) catalyst. We believe that our strategy will promote the synthesis of similar multifunctional block copolymers.
Keywords: Ni(0) regeneration; block copolymer; nickel-catalyzed cross-coupling reaction; proton exchange membrane; sulfonated polyphenylene.