Abstract:

A series of hydrophile- lipophile sequenced block ionomers with hydrophobic macrosegments and size- var-ying hydrophilic macrosegments was synthesized via a two- pot two- step nucleophilic polycondensation of bis(4- chlo-rophenyl) sulfone,9,9- bis(4- hydroxyphenyl) fluorene (BHF),bisphthalazinone containing biphenyl moiety andsulfonated 4,4- difluorobenzophenone (SDFBP),and was used as the material of proton exchange membrane.Then,the structure and properties of the ionomers were investigated.The results show that (1) the structure of theionomers is in good accordance with the designed backbone structure; (2) wet ionomers membranes exhibit a clearmicrophase separation structure with continuous hydrophilic and small- size isolated hydrophobic regions; (3) thesize of hydrophilic regions increases with the size of hydrophilic segments to hydrophobic segments,which benefitsthe swelling of hydrophilic regions and the formation of large- size proton conductive channels; (4) the synthesizedpolymers membranes possess good thermal stability,appropriate water absorption and swelling ratio,high protonconductivity,excellent mechanical properties as well as good high- temperature hydrolytic stability; (5) with thesize increase of large- size hydrophilic chains,the methanol penetration resistance of the membranes improves andthe oxidation resistance degrades; and (6) the proton conductivity of the membranes increases with temperature.Inparticular,the proton conductivity of ionomers 5c and 5d at 20℃ is close to or even higher than that of Nafion 117at 30℃,and the proton conductivity of ionomer 5d reaches 15.63 mS/cm at 80℃.

Key words: sequenced block ionomer, sulfonated block poly(aryl ether sulfone ketone), biphenol, phthalazi-none, proton exchange membrane fuel cell