Hydrogen bond cross-linked sulfonated poly(imino ether ether ketone) (PIEEK) for fuel cell membranes

A new diamine monomer, 3,3'-dihydroxydiphenylamine, is prepared by the palladium catalyzed C-N coupling reaction and the following reduction reaction of 3-bromoanisole and m-anisidine. A series of novel hydrogen bond cross-linked sulfonated poly(imino ether ether ketone) (SPIEEK) are obtained by the copolymerization of sodium 5,5'-carbonylbis(2-fluorobenzene sulfonate), 4,4'-difluorobenzophenone with 3,3'-dihydroxydiphenylamine. The structures of resulting polymers are characterized by means of FT-IR, H-1 NMR spectroscopy, and elemental analysis; the results show an agreement with the proposed structure. The resulting SPIEEK membranes display much better resistance to swelling than these without imino groups due to the strong interchain interaction through imino and sulfonic acid groups. The SPIEEK-60 and SPIEEK-80 membrane show the proton conductivity of 0.118 and 0.154 S cm(-1) at 80 degrees C which is higher than Nafion 117 (0.082 S cm(-1) at 80 degrees C). Moreover, the SPIEEK membranes exhibit good mechanical properties and lower methanol permeability due to the hydrogen bondings between the polymer chains. (C) 2015 Published by Elsevier B.V.