| In the anion exchange membrane fuel cell(AEMFC),anion exchange membrane(AEM)is one of the core components,which directly affects the performance of AEMFC.At present,there are two potential problems arrest the development of AEMFC:poor alkaline stability and low ionic conductivity.Therefore,the development of AEM with excellent performance is one of the main researches at this stage.In this work,two series of side-chain type photosensitive poly(arylene ether sulfone)anion exchange membranes were designed and prepared based on the molecular structure of anion exchange membrane.The effects of photocrosslinking,polymer structure and cationic groups on the performance of anion exchange membranes were discussed.Firstly,the CMPSF200 with a chloromethylation rate of 200%was synthesized by using chloromethyl methyl ether as the chloromethylation reagent.The photosensitive poly(arylene ether sulfone)PSCMPSF70 with a chalcone content of 70%respect to the chloromethylation rate was synthesized by reacting with the 4-HC.Through Williamson etherification and chlorination reaction,the side-chain type photosensitive PSPSF70-CMB130 was synthesized with the phenyl methyl ether structure on the side chain.The structure of the polymers was characterized by ~1H-NMR,FT-IR and UV-vis.The results revealed that the PSPSF70-CMB130 showed good photosensitivity with a maximum absorption peak at 340 nm.Under UV irradiation at room temperature,the>C=C<groups of the chalcone structure occurred a[2+2]photochemical reaction and formed crosslinking structure on the polymer side chain,and the maximum photocrosslinking degree can be reached to 78%.Then,the side-chain type quaternary ammonium UV-crosslinkable poly(arylene ether sulfone)anion exchange membrane(QPSPSF70-CMB130-TMA)was prepared by using trimethylamine as the quaternization reagent.Anion exchange membranes with different crosslinking degrees were prepared by different exposure times of UV light under a swollen state at room temperature.The solubility,thermal stability,mechanical properties,ion exchange membrane capacity(IEC),water absorption,swelling ratio,ionic conductivity,and alkali stability of QPPSF70-CMB130-TMA membranes before and after cross-linking were tested.The non-crosslinked QPPSF70-CMB130-TMA membrane showed good solubility in common solvents such as DMAc and DMSO,the water uptake and swelling ratio were 168.66%and 35.45%at 80 ~oC,respectively.After photocrosslinking,the membranes were insoluble in any organic solvent,the thermal and mechanical properties of the crosslinked membranes were significantly improved.The initial decomposition temperature and tensile strength of the crosslinked membrane was increased by 22 ~oC and 29.22 MPa,respectively.The IEC value of the membranes decreased slightly after crosslinking,while the water uptake and swelling ratio decreased significantly,and the maximum was reduced by 43.90%and 26.97%,respectively.The ionic conductivity of QPSPSF70-CMB130-TMA membranes increased with the increase of temperature before and after cross-linking,and could reach up to 74.25 mS/cm at 80 ~oC.The ionic conductivity of the cross-linked membranes decreased with subtle decline.After soaking in 1M NaOH solution at 60 ~oC for 20 days,the IEC value and ionic conductivity of the non-crosslinked membrane remained 67.61%and 66.44%,respectively.However,after crosslinking,the highest residual ion conductivity and the IEC value of the crosslinked membranes was 80.83%and 78.80%,respectively.It revealed that photocrosslinking could significantly improve the overall performance of the AEM.Compared with the main-chain type AEM membrane,The side-chain type QPSPSF70-CMB130-TMA membrane had a maximum swelling ratio of less than35.45%at 80 ~oC with equivalent IEC values,whereas the main-chain type AEM was damaged owing to the excessive water absorption.The side-chain type AEM with an IEC value of 1.42 had an ion conductivity up to 74.25 mS/cm,whereas the maximum ion conductivity of the main-chain type AEM with an IEC value of 1.66 was only 58.46mS/cm.After soaking in 1M NaOH solution at 60 ~oC for 7 days,the ionic conductivity remained only 50%for the main-chain type AEM with an IEC value of 1.66,while the ion conductivity of the side-chain type AEM was maintained more than 92%.Above all,the side-chain type AEM showed superior performance compared to the main-chain type AEM.Finally,The side-chain type piperidine salt UV-crosslinkable poly(arylene ether sulfone)anion exchange membrane(QPSPSF70-CMB130-MPRD)was prepared by using N-methyl piperidine as the quaternization reagent,and the anion exchange membranes(cQPSF70-CMB130-MPRD)with different crosslinking degrees were also prepared.The performances of QPSPSF70-CMB130-MPRD membranes before and after cross-linking were tested.The non-crosslinked QPSPSF70-CMB130-MPRD membranes showed good solubility in common solvents such as DMAc and DMSO,and the crosslinked membranes were insoluble in any solvent.The QPSPSF70-CMB130-MPRD membranes exhibited good thermal stability,mechanical property,alkaline stability and well-defined hydrophilic-hydrophobic phase separation structure before and after crosslinking.The initial decomposition temperature was in the range of 230~243 ~oC,the tensile strength was in the range of 27.22~47.93 MPa,and the IEC value was between 1.18 and 1.32 mmol/g.The water uptake and swelling ratio were 125.48%and 32.77%at 80 ~oC,respectively,and the ion conductivity was in the range of 60.34~72.93 mS/cm.After soaking in 1M NaOH solution at 60 ~oC for 20 days,the membranes did not show substantial changes,and the residual ionic conductivity was up to 87.96%.Compared with the side-chain type quaternary ammonium membrane,the side-chain type QPSPSF70-CMB130-MPRD membranes exhibited camparable ionic conductivity and better alkali stability at low IEC values and water uptake.It revealed that the piperidine salt type AEM possesses superior performance compared to the quaternary ammonium type AEM. |
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