Synthesis And Characterization Of Anion Exchange Membranes Based On Poly(Arylene Ether)s For Fuel Cell

Polymer electrolyte membrane fuel cells have drawn more and more attractions as a new, high efficiency and environmental friendly energy system, where the polymer electrolyte membrane serves as one of its key components. In this thesis, a series of novel anion exchange membranes (AEMs) derived from poly(arylene ether)s (PAEs) were succefully prepared, and their fundamental properties were evaluated for anion exchange membrane fuel cells (AEMFCs) applications in detail.A series of anionic polymers based on poly(arylene ether sulfone)s (PAES) have been prepared through condensation polymerization, chloromethylation and qurternization using4,4’-difluorodiphenyl sulfone (DFDPS) and2,2’-bis(4-hydroxyphenyl) propane (BPA) as the starting material, where the molar ratio of DFDPS and BPA was controlled to be1:1. And the obtained PAESs were used to prepare AEMs through solution casting. The chemical structures of the PAESs and the corresponding chloromethylated polymerss were confirmed by’H NMR spectra. AEMs of linear-type quaternary poly(arylene ether sulfone)s (QPAES) and self-crosslinked quaternary poly(arylene ether sulfone)s (CQPAES) were prepared using trimethylamine and N, N, N’,N’-tetramethylhexyldiamine (TMHDA) as the quaternization reagent, respectively, and their properties were investigated. The results showed that the IEC, water uptake and hydroxide ionic conductivity decreased with the increase in the amount of TMHDA. In the cases of r=0.75, it caused partial chloromethyl groups imbedded in the polymer matrix due to the rapid reaction of tertiary amine and chloromethyl groups, which led to the decrease in IEC and changes in the membrane properties. The CQPAES membranes displayed much lower water uptake and size change compared with the QPAES membranes with the similar ion exchange capacity (IEC) in water. The CQPAES membranes showed quite good dimensional stability at high temperature especially. The membrane of CQPAES-5with IEC of1.81mmol/g showed conductivity of30mS/cm and85mS/at30℃and90℃, respectively. All the CQPAES membranes kept toughness level of V after the alkaline stability test at60℃.According the results obtained mentioned above, a series of self-crosslinking CQAPES membranes were successfully prepared based on the prepared PAES polymers, using N, N, N’, N’-tetramethylethylenediamine (TMEDA), N, N, N’, N’-tetramethylpropylenediamine (TMPDA) and TMHDA as the quaternary reagent, respectively, after chloromethylation of the PAESs. And the influence of the quaternary reagent on properties of membranes was investigated. The results indicated that the TMHDA could react with chloromethyl groups more sufficiently than TMPDA and TMEDA And the CQPAES-H series membranes displayed better mechanical properties, water stability and alkali stability.A series of PAES/CMPAES blend membranes with different IECs were successfully prepared by solution casting from PAES and the chloromethylated polymer CMPAES, and their properties were investigated. The results indicated that the blend membranes displayed lower water uptake, fairly enhanced Young’s Modulus and dimensional stability compared to the QPAES membranes. The blend membranes kept toughness level of V after the alkaline stability test at60℃, indicating the performance improvement for the AEMs by organic/organic blend modification.A new functional monomer,2,2’-dimethylaminemethylene-4,4’-biphenol (DABP), was prepared from4,4’-biphenol (BP) through Mannich reaction. The fluorinated poly(arylene ether)s (PFAE)s with pendant quaternary ammonium groups were prepared by copolymerization of DABP, BP and decafluorobiphenyl. Corresponding AEMs were prepared by further quaternization with iodomethane and alkalization. It was found that the IEC values obtained by titration were much lower than the theoretical IEC values due to the insufficient quaternization procedure. However, the membrane of QPFAE-60with IEC of0.5mmol/g showed conductivity of11mS/cm at60℃.