Preparation And Properties Of Crosslinked Structure Proton Membrane Based On SPI - SPAE Semi - Interpenetrating Network

The direct methanol fuel cell (DMFC) has received considerable attention owing to low emission of pollutants and the direct conversion of chemical energy into electrical energy. Proton exchange membrane (PEM) is the most important components of a direct methanol fuel cell. There are many kinds of PEMs such as perfluorinated membranes, partially fluorinated membranes and non-fluorinated membranes. Recently, extensive efforts have been focused on developing PEMs based on non-fluorinated sulfonated hydrocarbon polymers because of their low emission of pollutants. However, the high swelling degree of non-fluorinated membranes or in methanol solution at high sulfonation degree has been recognized as one of the main drawbacks, which limits its further DMFC application. There are three methods to improve the performance of proton exchange membrane, doping inorganic materials, polymer blending, crosslinking and so on. In this thesis, two kinds of blend membranes of sulfonated poly(arylene ether ketone)(SPAEK) and sulfonated polymide (SPI), sulfonated poly(arylene ether sulfone)(SPAES) and sulfonated polymide (SPI) were respectively prepared. The corresponding cross-linked semi-interpenetrating polymer network membranes were achieved by cyclocondensation reaction with crosslinking agent. To study the effect of different structures on the properties of PEM, the properties of these membranes were investigated. The work includes the following aspects:1. SPI was prepared by4,4’-bis(4-aminophenoxy) biphenyl-3,3’-disulfonic acid (BAPBDS),3,4,9,10-perylene tetracarboxylic dianhydride (PTDA) and4,4’-bis(4-aminophenoxy)biphenyl (BAPB). SPAES or SPAEK was synthesized by4,4’-biphenol (BP),2,6-difluorobenzil (DFB) and3,3’-disulfonated-4,4’-difluorodiphenyl sulfone disodium salt (SDFDPS) or5,5’-carbonyl-bis (2-fluorobenzene sulfonate)(CBFBS).2. SPI, SPAEK and SPAES proton exchange membranes were respectively prepared by casting the solution onto glass plates and drying. Four blend membranes with different ion exchange capacity (IEC) were prepared too. Then four kinds of cross-linked semi-interpenetrating polymer network membranes (Semi-IPN) were prepared through cyclocondensation reaction with3,3’-diaminobenzidine (DAB) to form quinoxaline groups acting as crosslinking.3. The properties of these membranes such as water uptake, solvent uptake, size change, proton conductivity, methanol permeability, mechanical properties, and stabilities were investigated. By comparing the properities of the PEMs, the effect of structure on membrane properties was studied. The properties of blend membranes are between the SPI membrane and SPAE membranes. The water uptake, size change, methanol permeability, mechanical properties, and stabilities are more excellent than blend membranes and SPI membrane and SPAE membranes. For example, after blending, the water uptake of the SPI-SPAES membrane is53%, while the SPI membrane is50%and the SPAES membrane is59%. After cross-linking, the methanol permeability of the Semi-IPN membranes reduced by79%and antioxidant time improved to double,the water uptake reduced by60%and the in-plane dimensional size reduced by68%.