Polymer composite membrane of sulfonated and nonsulfonated polysulfone for direct methanol fuel cell

Abstract

In order to enhance the proton conductivity and to reduce the methanol crossover in the direct methanol fuel cell(DMFC) the polymer blend membranes composed of proton conducting component and methanol barrier component were prepared. Sulfonated poly(arylene ether sulfone) copolymer with 60mol% sulfonation (sPAES-60) was synthesized via poly-condensation reaction from 3,3’-disulfonated -4,4’-dichlorodiphenyl sulfone (SDCDPS), 4,4’-dichlorodiphenyl sulfone (DCDPS), and 4,4’-biphenol(BP) for the proton conducting component. To compensate for the mechanical and chemical weakness of the sPAES-60 and to reduce the methanol permeability poly ether sulfone copolymer (RH-2000, Solvay) was used. By varying the drying condition (HT, FD1, FD2) and the concentration of the casting solution (10wt%, 15wt%, 20wt%) various types of phase separated morphologies of the blend membranes were obtained. The morphology was characterized by SEM, EDAX, and AFM. The AC impedance spectroscopy was used to measure the proton conductivity and the liquid permeability measuring instrument was designed to measure the methanol permeability. The state of water in the membranes was confirmed by the DSC and it was used to correlate the morphology of the membrane with the membrane transport properties. In this thesis the effect of the drying condition on the phase separation and morphology of the blend membranes was investigated and then the transport properties of the blend membranes were discussed.