| Proton exchange membrane fuel cell?PEMFC?is one of the most promising clean energy devices in future that converts chemical energy directly into electrical energy.In the PEMFC,fuel and oxidizer reacts separately in the anode and cathode which are insulated by the proton exchange membrane?PEM?.PEM is one of the key components for the PEMFC in obstructing fuel and oxidant,isolating electrons and conducting protons,and also determines the operating temperature of the device.In this paper,sulfonated poly?arylene ether sulfone?s was studied as an important aromatic proton exchange membrane material.A series of novel multiblock side-chain type sulfonated poly?arylene ether sulfone?were prepared and their properties were studied.Bis?4-fluoro-2-?3-sulfonic sodium benzoyl??phenyl sulfone?BFSBPS?was applied as sulfonated monomer that has been synthesized in our group.BFSBPS and bisphenol with different structures were reacted to generate hydrophilic segments.4-fluorophenyl sulfone and bisphenol with different structures were reacted to prepare the hydrophobic oligomers.A series of multiblock side-chain type sulfonated poly?arylene ether sulfone?s with different chain lengths were prepared by two-pot reaction method.The proton exchange membranes were obtained by solution casting method,and their basic properties were also characterized such as ion-exchange capacity?IEC?,water uptake,dimensional stabilities,mechanical properties,proton conductivity,oxidative stability and water stability.Multiblock side-chain type polymers with different chain lengths were prepared by the method of two-pot polymerization.The structures of multiblock copolymers were characterized by FT-IR and 1HNMR spectra,and the heat resistance was tested by the thermo gravimetric analysis?TGA?.All of these multiblock polymer based PEM showed the heat decomposition temperature over 350?.When the both of the hydrophobic and hydrophilic block length and ion exchange capacity of the multiblock copolymer increased,the water uptake and proton conductivity increased while the oxidative stability decreased.The multiblock side chain type PEMs showed anisotropy in dimensional change.The size change value in the film thickness direction was higher than that of the film plane direction.The mechanical properties test showed that the most of maximum tensile strength of the membranes were above50 MPa,and the highest was 63 MPa for B3,and the elongation at break was above10%at 20?,20%relative humidity,which could meet the requirements of proton exchange membrane fuel cells.A series of sulfonated poly?arylene ether sulfone?proton exchange membranes with the same chain lengths of 10 for both of hydrophobic and hydrophilic block but varying the bisphenol moieties to hydroquinone and hexafluorobisphenol A were prepared.The basic properties of the polymer and proton exchange membranes were investigated.The results showed that they had good thermal stability with the thermal decomposition temperature of the polymer films were above 350?.With similar IEC and the same length of the chain the introduction of hydroquinone in the sulfonation zone of the polymer in result to the increasing of swelling ratio of PEM when compared to that of the bisphenol.However,the sulfonated groups were more dense and significantly improved the proton conductivity of PEM.For example,B10 with the IEC of 1.37meq g-1 showed proton conductivity of 158 mS cm-1 in water at 60?,which is higher than that 146 mS cm-11 for Nafion112 and 94 mS cm-1 for B5 with the bisphenol.The hexafluorobisphenol A was introduced as hydrophobic segment with higher flexible and hydrophobic properties,which was beneficial to improve the micro-phase separation structure of the PEM,hence the increasing of proton conductivity for PEMs.For example,the B5 with IEC of 1.34 meg g-1 showed lower proton conductivity(94 mS cm-1)than that of the membrane of B11(129 mS cm-1)with the similar IEC of 1.40 meg/g in water at 60?. |
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