Syntheis And Properties Of Novel Polyethersulfones Anion Exchange Membrane

It is well known that polymer electrolyte fuel cell based on anion exchange membrane has demonstrated advantages of high energy conversion efficiency, using non-noble metal catalysts, low pollution and maintenance etc., therefore, it is expected to be one of the most promising clean energy technology. The development of new type of anion exchange membrane so far has attracted more and more attentions.This article is based on a series of studies and preparation of functional polyether sulfone anion exchange membrane material. The main points of the thesis are as follows.(1)In this paper, a block copolymer containing methyl side group was first synthesized from methylhydroquinone and 4-fluorophenyl sulfone with polycondensation.Afterwards, through NBS bromination, quaternary ammonium salt conversion, a kind of anion block copolymer polyether sulfones with quaternary ammonium pendant groups was finally synthesized. After finishing the synthesis job,polymer structure was confirmed the by1 H NMR and then investigated the properties of the obtained block copolymers. With comparison to the random copolymer containing the same starting materials and IEC, the block polymer membranes did demonstrate lower water uptake, swelling rate, better dimensional stability and higher conductivity. An IEC of 1.45 meq/g with hydroxide conductivity of 43.6 m S/cm at80 ℃.There was no loss of conductivity after a 7 day immersion in 4 M Na OH at r.t.( 2) In addition, this paper have a tentative trial on direct polymerization:polycondenstaion starting from functional monomer as quaternary ammonium salt.First a necleophilic reaction between 4-fluorophenyl sulfone and methylhydroquinone has been implemented and the obtained difluoro-substituted compound goes through NBS bromination, quaternary ammonium salt conversion and finally becomes quaternary ammonium salt monomer. Direct polymerization with the above quaternary ammonium salt monomer, 4-fluorophenyl sulfone and bisphenol AF can be done to directly synthesize polyether sulfones anion exchange membranes with quaternary ammonium pendant groups and the structure of product was determined by1 H NMR. The tentative trial confirmed that direct polymerization starting from quaternary ammonium salt monomer is applicable to directly synthesize quaternary ammonium salt polyether sulfones as anion exchange membranes. Indeed, this trial gives us unique opportunity to precisely control of the amount of quaternaryammonium groups and their locations through molecular architecture. By the way all the membranes from direct polymerization showed good thermal, mechanical,alkaline stabilities An IEC of 1.15 meq/g with hydroxideconductivity of 35.8 m S/cm at 80 ℃. The results also further confirmed that direct polymerization opens a window for us to design materials through molecular architecture.