| Fuel cells, electrochemical devices converting chemical energy into electric energy via redox reaction, have attracted more and more attention in the ubiquitous energy-dependent world due to low power-source emissions and high conversion efficiency. In particular, proton exchange membranes (PEMs) play a dominant role in this system. Perfluorosulfonic acid membranes such as Nafion (DuPont) have been recognized as the current choice for PEMs because of their high proton conductivity and excellent stability. However, their disadvantages of high cost, low operation temperatures, and high methanol permeability have stimulated extensive research into the investigation of promising alternatives.In recent years, many kinds of sulfonated aromatic polymers have been studied as the promising candidates for PEMs because of their low methanol permeability, excellent thermal and chemical stabilities. However most of these sulfonated aromatic polymers formed bonds with sulfonic acid groups directly to the main chain, which showed less pronounced nanophase separation and more dead-end channels than that of Nafion. It has been found that the nanophase separation between hydrophilic and hydrophobic domains could be improved, if the sulfonic acid groups were located onto the flexible pendant side chains, which made the hydrophilic sulfonic acid group regions separated from the hydrophobic polymer main chain. And the microscopic phase separation is responsible for proton conduction and morphological stability. Hydrogen bonded is a critical factor in determining the physical and mechanical properties of many polymeric materials. It has been reported that inter- and intramolecular hydrogen-bonding interactions between sulfonic acid and hydroxyl groups have been used to improve the properties of PEMs.In this study, we reported a novel sulfonated hydroxynaphthalene poly(aryl ether ketone)s (SHNPAEKs) containing both sulfonic acid on the side chain and hydroxyl groups in the structure. Then a series of hybrid membranes based on sulfonated poly(arylene ether ketone)s (SNPAEK), polysiloxane (KH-560) and sulfonated curing agent (BDSA) has been prepared by sol-gel and cross-linking reaction for optimizing the performance of the PEMs.In chapter 3, the monomer DMNF was prepared via FriedeleCrafts acylationof 2,6-dimethoxylnaphthalene with 4-fluorobenzoyl chloride catalyzed by anhydrous ferric chloride. And then the MNPAEK were synthesized via polycondensation reactions. The conversion of MNPAEK to HNPAEK was conducted in CH2Cl2 using BBr3. The sulfobutyl groups can be grafted onto HNPAEK by nucleophilic ring-opening reaction with the 1,4-butane sultone. A series of SHNPAEK-xx with different sulfonate and hydroxyl groups content was prepared by tuning up the amount of 1,4-butane sultone. The calculated Ds values from 1H NMR spectra were almost the same as the expected Ds derived from the feed ratio. This result indicated that the Ds values could be well controlled by adjusting the amount of 1,4-butane sultone. The SHNPAEK-xx series membranes possess good thermal and mechanical stability. The SHNPAEKs hold better dimension stability than the other main-chain-type SPAEKs with similar or even low IEC values. Compared to the main-chain-type SPAEKs, SHNPAEKs attaching the sulfonic groups on pendants could lead the hydrophilic/hydrophobic separation more obvious thus enhancing the proton conductivity of the ionomers. For example, the proton conductivity of SHNPAEK-90 reached 0.197 S cm-1 at 80℃. The methanol permeabilities of SHNPAEKs were in the range of 2.65×10-7-11.9×10-7 cm2 s-1,which were lower than the value of Nafion 117 (1.61×10-6 cm2 s-1).In chapter 4, we demonstrate a novel hybrid membrane for DMFC by using a sulfonated curing agent to form polysiloxane cross-linked network. The hybrid SKB-xx membranes were prepared via oxirane ring cleavage and sol-gel reaction. The reaction between epoxy of KH-560 and amine group of BDSA via oxirane ring cleavage leaded to the organic polymeric network, while the hydrolysis of Si-(OR)3 catalyzed by H+ leaded to the cross-linking inorganic siloxane network. The cross-linked siloxane network in the hybrid membrane is temperature tolerant and can improve the heat resistance of membranes. And the mechanical properties of SKB-xx membranes in dry states showed they were strong and flexible enough to be used as PEMs. Meanwhile, the oxidative stability of the SKB-xx series membranes was increased with the amount of Si-O-Si and epoxy cross-linking structures. It had been found that the introduction of KH-560 and BDSA greatly reduces the water uptake of the membranes. All the membranes showed comparable proton conductivity to Nafion 117. For SKB-5, its proton conductivity was 0.192 S cm-1 at 80℃, which was higher than the 0.146 S cm-1 of Nafion 117. And the proton conductivity of SKB-5 and SKB-10 reached to 0.192 and 0.179 S cm-1 at 80℃, respectively, which was higher than the 0.175 S cm-1 of SNPAEK. After cross-linking reaction, the methanol permeability of SKB-xx membranes were 4.67×10-7-8.20×10-7 cm2 s-1, which were much lower than that of the SNPAEK (12.11×10-7 cm2 s-1). The selectivity of all the hybrid membranes was higher than the pristine SNPAEK membrane. SKB-10 showed the highest selectivity which was as much as 2.5 times than the SNPAEK.
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