Preparation And Properties Of Multiblock Sulfonated Poly (Arylene Ether Sulfone)s For Proton Exchange Membrane Applications

Proton exchange membrane fuel cells (PEMFCs) have drawn many attractions as a new and high efficiency energy resource where the proton exchange membrane (PEM) serves as one of its key components. In this dissertation, several types of novel PEMs derived from sulfonated poly(arylene ether sulfone)s (SPAES) were succefully prepared and their fundamental properties were evaluated for PEMFC applications in detail.By multiblock copolymerization method, a series of multiblock SPAES was successfully prepared with controllable rigidity of polymer backbones through varying the bisphenol moieties. The chemical structures of the resulting polymers were confirmed by 1H NMR spectra. The results indicated that the membranes derived from 9,9'-(4-fluorenylidene) diphenol (BHPF) displayed the lowest water uptake, dimensional change and best stability toward water as well as proton conductivity with the similar ion exchange capacity (IEC). For example, the membrane with IEC of 1.70 meq/g showed proton conductivity of 23 mS/cm under 50% relative humidity at 60℃, which was comparable to that of Nafion 112.A series of multiblock SPAES was successfully prepared by adjusting the block length of sulfonated/nonsulfonated moieties with BHPF and hexafluoro bisphenol-A as the sulfonated and nonsulfonated moiety, repectively. The results indicated that the membranes displayed increasing water uptake, proton conductivity and decreasing stability toward water and mechanical properties with the increase in block length. The membranes with sulfoanted/nonsulfoanted block length of 10/10 exhibited the best comprehensive properties, for instance, the membrane with IEC of 1.43 meq/g showed proton conductivity of 30 mS/cm under 70% relative humidty at 60℃, weigh loss of only 2.7% after water stability test. They also showed high water uptake and proton conductivity at low relative humidites than the random ones.Meanwhile, composite membranes were successfully prepared from multiblock SPAES and nano-TiO2 by solution mixing method. The results indicated that the composite membranes displayed fairly enhanced water uptake, Young's Modulus and dimensional stability compared to the blank SPAES membranes. The proton conductivity of the composite membrane was higher than that of the blank SPAES membranes, in the water. So nano-TiO2 can improve the proton exchange membrane performance to some degrees.