Synthesis And Characterization Of Sulfonated Poly(Arylene Ether)Proton Exchange Membrane Containing Phosphine Oxide Group

Proton exchange membrane is one of the important components of proton exchange membrane fuel cell.Today,the main commercialization is perfluorosulfonic acid membranes.However,these membranes have many disadvantages that limit their development.As a result,sulfonated aromatic polymer proton exchange membranes came into being as an alternative.Sulfonated poly(arylene ether phosphine oxide)s is a kind of aromatic polymer membrane with excellent performance.In this paper,a series of sulfonated poly(arylene ether)proton exchange membranes containing phosphine oxide were synthesized by direct polycondensation.First,the dihydroxydiphenyl ether monomer was introduced into the polymer to obtain a series of monosulfonated poly(aryl ene ether phosphine oxide)s(msPEPO-x)containing diphenyl ether with different degrees of sulfonation,and prepared transparent,tough and flexible membranes.The results showed that these msPEPO membranes displayed outstanding properties in terms of proton conductivity and oxidative stability.At the same time,the electrical conductivity can be improved by increasing the degree of sulfonation while maintaining dimensional stability.For example,msPEPO-80 exhibited a proton conductivity of 0.092 S cm-1 higher than that of Nafion 117(0.088 S cm-1)at 80℃.It took 60 h to dissolve completely in Fenton’s reagent(25 ℃,30%H2O2,30 ppmFeSO4),which presented remarkable oxidation stability.Therefore,the achieved membrane has an excellent application prospect.In order to reduce the swelling of the above membrane,the monosulfonated phosphine oxide monomer in the above polymer was replaced by a trisulfonated phosphine oxide monomer.By changing the distribution of sulfonated monomers to adjust the distribution of sulfonic acid groups,a series of trisulfonated poly(arylene ether phosphine oxide)s(tsPEPO-x)was prepared to improve the swelling of the membrane.The results showed that the dimensional stability of the trisulfonated membrane with the same sulfonati on degree has been significantly improved.For example,the conductivity of tsPEPO-120 is 0.093 S cm-1 at 80℃ which is higher than 0.087 S cm-1 of Nafion117,the swelling ratio of tsPEPO-120 is 23.5%equivalent to that of Nafion117(20%).Morever,the membrane also has good resistance oxidative stability in Fenton’s reagent at 80℃.Therefore,tris-ulfonated structure can produce membranes with better performance than mono-sulfonated structure.In order to further improve the performance of the membrane,phthalazinone hydroxyl monomers were introduced into the polymer to form intermolecular hydrogen bonds,and trisulfonated poly(arylene ether phosphine oxide)s(tsPPEPO-x)was obtained.The results showed that the dimensional stability of the resulting membrane was further improved.For example,the electrical conductivity of tsPPEPO-120 at 80℃ is 0.066 S cm-1,which is close to that of Nafion117,and the swelling ratio is 11.5%,which is almost half that of Nafion117.At the same time,the membrane has good oxidation resistance in Fenton’s at 80℃.This type of membrane shows good comprehensive performance and has potential application value.