Preparation And Propetries Of Poly (Arylene Ether) Proton Exchange Membranes Based On Post-sulfonation

Fuel cells have been greatly developed during the past decade with the growing demandsfor efficient, reliable and environmentally friendly energy sources. They possessed lots ofadvantages such as environmental friendliness as well as other advantages, such as highenergy conversion efficiency, low temperature start, no electrolytic cell leakage, no corrosion,long life and so on. All commercial available membranes bearing pendant sulfonic acidgroups, which exhibit high conductivity and excellent chemical stability. Because of theirhigh cost, low operation temperature and high fuel permeability, there is a continuousdemand to develop the nonfluorinated hydrocarbon ionomers as an alternative to replacecurrent perfluorinated membranes.Sulfonated poly (arylene ether) materials have been widely studied as one of thepotential to become alternative to perfluorinated sulfonic acid membrane due to its goodthermo-chemical stability, high resistance methanol and hydrolysis properties and structuraldiversity. The study indicated that main-chain type sulfonated poly(arylene ether)s containinghigh levels of sulfonic group easily lead to excessive swelling and lost the dimensionalstability as a consequence. To solve this problem, several attempts have been made in ourwork, such as designing block structure, introducing polar groups, acid-base complex andcovalent cross-linking. And the effects in thermal stability, mechanical properties, waterabsorption, dimensional stability, methanol permeability and proton conducting propertieswere thoroughly investigated.First, a new series of novel PAEEKKs simultaneously bearing sulfonic acid andcarboxylic acid groups on the pendants through a postsulfonation procedure followed by ahydrolysis reaction. The properties including thermal, oxidative and dimensional stability,water absorption, mechanical properties, proton conductivity and methanol crossover of bothsulfonated and sulfonated/carboxylated polymers were well investigated. In addition, the effects of the carboxyl acid groups on the properties of the novel PEMs were studied.Second, a new family of sulfonated fluorenyl-containing poly(ether ether ketoneketone)s (SFPEEKKs) were successfully synthesized through a mild postsulfonation inconcentrated sulfuric acid at room temperature. A series of molecule-enhanced blendmembranes were prepared based on SFPEEKKs and an amino-functionalized poly(ether etherketone) by solution casting method. These blend membrans showed higher thermal stability,lower swelling ratio and methanol permerbilities and better mechanical properties incomparison with pristine SFPEEKK membranes.Third, fluoroene-containing sulfonated poly ether ether ketone ketone (SPEEKK)synthesized was chose as a matrix, and the AmPOSS was chosen as a filler to form acid/baseinteraction with the sulfonated rigid backbone by solution casting. The basic properties werewell investigated,the results showed that the composite membranes showed much lowerswelling ratio,better selectivity without excess decrease of proton conductivity.