Systematic study of the synthesis and characterization of 3,3'-sulfonylbis(6-chloro benzenesulfonic acid) disodium salt monomer for proton conducting polymeric membranes in fuel cell applications

摘要

The copolymers based on the monomer 3,3'-sulfonylbis(6-chlorobenzenesulfonic acid) di-sodium salt, abbreviated as SDCDPS in this paper, are found to have very promising properties for developing cost effective alternate proton exchange membranes. The synthesis and characterization of this monomer by sulfonation of dichloro diphenyl sulfone (DCDPS) was briefly discussed by Ueda et al. During the extensive studies conducted in our laboratory on the various copolymer of this monomer, we have found that purity of SDCDPS, as expected, plays a very important role in obtaining copolymers of high molecular weight and hence possessing better film properties. As a part of continuation of this project, it was required to scale up the monomer and polymer synthesis. This prompted us to conduct a systematic investigation of the synthesis and characterization of SDCDPS. The issues we focused on include: 1) time and temperature required for the reaction in order to obtain good yields, 2) identifying the impurities formed in the di-sulfonation reaction, and 3) choosing the best solvent combination for the recrystallization in order to get high purity monomer with constant water content. The optimization of these various process control parameters is expected to define quality control criteria for scale up production of the monomer in high yield and purity with good consistency.