Preparation Of Crosslinked Anion Exchange Membranes Based On Polymer Of Intrinsic Microporosity

As the core component of alkaline fuel cells,anion exchange membranes(AEMs)play a decisive role in the working life and power density of fuel cells.However,there are still many drawbacks in the AEMs,such as low ion conductivity,poor alkaline stability and insufficient dimensional stability.Generally speaking,the most direct method to obtain high ionic conductivity is to increase the ion exchange capacity(IEC)of AEMs.However,a high IEC will cause the membrane to absorb excessive water and cause swelling,and the results is that dimensional stability of AEMs will be reduced.Meanwhile,too high IEC will reduce the alkali resistance of AEMs.Therefore,how to balance the relationship between them and produce high-performance AEMs is one of the difficulties in the field of membrane preparation.To this end,in this paper,two types of crosslinked AEMs based on PIMs were designed and prepared by adjusting the membrane microstructure to construct efficient ion channels,and the relationship between the structure and performance of AEMs was discussed in depth.The main works and results are showed as follows.(1)In order to solve the problems of poor solubility of PIMs and difficult graft functionalization,which leads to the preparation of AEMs difficultly.The versatile strategy to design the innovative microporous polymers PIM-1/PES with the rigid PIM segment and flexible reaction segment for the preparation of the high-performance AEMs was proposed.The polymer shows good solubility in common polar solvents and high reactivity.Then,a series of crosslinked AEMs were prepared.After that,structure and electrochemical performances of the prepared AEMs was investigated in details.The results show that the introduction of the hydrophobic rigid PIM-1 segment into the main chain can not only effectively limit the swelling of the membrane,but also effectively promote the aggregation of ionic groups,make the microphase separation structure more obvious,and then form a developed ion transmission channel.The prepared crosslinked PIM-1/PES0.50 AEM has a higher ionic conductivity(87.6 mS cm-1,80?),which is 36%higher than that of the PES AEM,and a lower swelling(11%,80?).Membrane-electrode assembly prepared by the PIM-1/PES0.50 AEM has the high-power density of 150 mW cm-2 at 60? in the H2/O2 fuel cell,showing a good application prospect.(2)Based on the above studies,crosslinked AEMs with PIM polymers with tertiary amine groups as cross-linking agents were designed,and the structure characterization and performance testing of the membrane were performed.Studies have shown that the introduction of PIM-based macromolecular crosslinking agents can significantly increase the free volume in AEMs,thereby increasing the water content of the membrane,and also beneficial to self-aggregation of hydrophilic PPO fragments in AEMs.The microphase separation structure increases the size of ion clusters and improves the ionic conductivity.When the crosslinker ratio is 1.50,the crosslinked CPPO-PIM1.50 AEM has the highest ionic conductivity(120 mS cm-1,80?).And the film has good anti-swelling ability,which greatly improves its potential in practical applications.In summary,crosslinked AEMs with rigid PIMs main chain structure and crosslinked AEMs modified with rigid PIMs cross-linking agent were prepared.The effects of rigid PIMs main chain modification and rigid PIMs crosslinker modification on the performance of AEMs were discussed.The research results have certain guiding significance for the exploitation of PIMs AEMs.The prepared PIM-1/PES0.50 and CPPO-PIM1.50 AEMs have potential application prospects in the fields of fuel cells,water treatment,and chemical separation.