Studies On Synthesis And Properties Of Novel Poly(Aryl Ether Sulfone)S-based Anion Exchange Membrane For Fuel Cells

Recently fuel cells have become a research hotspot because of their high fuel efficiency, low pollution products as well as many choices of fuel resources, wherein the alkaline membrane fuel cells(AMFCs) with low cost is catching lots of attention. However, anion exchange membrane inside AMFCs, the key component, is facing challenge on the trade-off point between conductivity and mechanic properties for membranes. Therefore, this thesis focuses on meolcular architecture design with the new base monmer so as to chase high conductivity with improving while maintaining the mechanic properties of membrane.In the thesis, a new monomer 3,3’-bismorpholinomethyl-4,4’-dihydroxybiphenyl(DMPBP) was syntheized through mannich reaction using 4,4’-dihydroxybiphenyl, paraformaldehyde and morpholine as raw materials. Then a random copolymer was syntheized through polycondensation of DMPBP at different molar ratios to total dihydroxyl monomers, bisphenol A and 4-fluorophenyl sulfone. Afterwards, the obtained random copolymer(PESQN-X, X is the molar ratio of new base monomer to total dihydroxyl monomers) was converted into alkaline polymer(PESQNI-X) via quaternary ammonium reaction. The alkaline membrane(PESQNOH-X) demonstrated a high electrical conductivity and still maintained certain mechanic properties. With high ion exchange capacity(IEC) of 2.16 mmol/g at 80 oC, PESQNOH-80 membrane can perfrom 8.01×10-2 S/cm conductivity at 110% water uptake. At this level of IEC, the overall performance of PESQNOH-80 membrane is much better than that of most reported anion membranes so far.Furthermore, the thesis moved to the next stage to make block copolymer through molecular architectural design approach. First one F-end oligomer with polymerization degree(DP) at 4 was prepared with the new monomer DMPBP and 4-fluorophenyl sulfone. Then a series of block polymers(BPESTN-X) were syntheized with different molar ratios of oligomer to total F-end monomers. Afterwards, the obtained block copolymer was converted into alkaline polymer(BPESQNI-X) via quaternary ammonium reaction. The block alkaline membrane(BPESQNOH-X) demonstrated excellent mechanical properties and alkaline stability over the above random copolymer and still maintained a high electrical conductivity as well. With ion exchange capacity(IEC) of 2.21 mmol/g at 80 oC, BPESQNOH-60 membrane can perfrom 5.32×10-2 S/cm conductivity at 40% water uptake. All results proved that these block copolymer membranes had application potential as alkaline membrane fuel cells. The main reason is that there are much more pronounced microphase separations between hydrophilic domains by the side chain and hydrophobic domains inside main chain, which facilated the formation of continuous ion channels in the membranes.