Synthesis And Properties Of Photosensitive Multi-block Sulfonated Poly(Aryl Ether Sulfone) Used As Pronton Exchange Membrane

Proton exchange membrane fuel cells (PEMFC), as a new efficient andenvironmental friendly energy technology, have received much attention fromscientific research and manufacturing industries all over the world. Sulfonated groupsin the block polymers can aggregate easily and form well connected ionic channels,which will support the proton conducting through the membrane. But highlysulfonated membranes will lead to poor dimensional properties, oxidative andhydrolytic stabilities, and mechanical properties, crosslinking method can overcomethose problems. Synthesis photosensitive Sulfonated multiblok poly(aryl ethersulfone)s is a well-proven method.4DHC and DFDPS was used to sythesize hydrophobic segment anddecafluorobiphenyl was the capping agent; biphenyl (BP) and SDFDPS was used tosynthesize hydrophilic segment; the multiblok sulfonate copolymer(SPAES11-11,SPAES15-11, SPAES18-11) with IEC (1.6-1.9meq/g) was synthesized by coulping thetwo segments. The structure of the polymers were confirmed by~1H-NMR and FT-IR,and the molecular weight was characterized by intrinsic viscosities. The logarithmicviscosity numbers were between1.2-2.8.The polymers revealed to have good solubility and good photosensitivity. Thepolymers can solute in aprotic solvent, such as DMF, DMAC, NMP; but insolubleafter phtocrosslinking. The wavelength of maximum absorption was at330nm, andthe absorbance decrease with the increase of UV irradition time, the crosslinkingdegree can reach60%after irradition for15min at the room temperature. The SPAEShad good thermal stability and the decomposed temperature of sulfonate group wereabove220℃and the main chain of the membranes were started to decompose at420℃. The decomposed temperatures of sulfonate group in the SPAES11-11-UV andSPAES15-11-UV were110and50℃higher than the uncrosslinked polymers.The polarizing microscope was used to select the proper solvent of theSPAES15-11, and DMAC was choosed as the optimum solvent. The SPAESmembranes were prepared by solution cast method and the crosslinked membranescould be gained by UV light radiating for15min. The water uptaken, swelling ratio,ion exchange capacity (IEC), hydrated constant, oxidative and hydrolytic stability,and thermal stability of the polymer before and after UV irradiation werecharacterized. With more sulfonated groups in the membrane, the higher IEC, and thelarger water absorption and swelling ratio, poorer oxidative and hydrolytic stabilities. After cross-linking in the swollen state, IEC of the membranes were maintained andthe water absorption and swelling ratio of the membranes were significantly reducedand the oxidative hydrolytic and thermal stabilities were enhanced.The microstructure of the polymers was characterized by SXAS, the resultrevealed that the ion clusters had formed and the distance between the clusters wasabout2nm,1.64nm and1.61nm for SPAES11-11, SPAES15-11, SPAES18-11, respectively.