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Preparation And Properties Of A Highly Durable Long Side-chain Polybenzimidazole For Anion Exchange Membrane

Posted on:2019-08-29Degree:MasterType:Thesis
Country:ChinaCandidate:S LiFull Text:PDF
GTID:2371330566484089Subject:Polymer materials
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In recent years,because of more and more serious energy crisis' s question,the country set up a new license plate of the new energy vehicles to develop new energy vehicles,and this act shows that the country pay great attention of the new energy.As an important part of new energy vehicles,fuel cell vehicles are clean,efficient and pollution-free,and it's possible to replace the fossil energy vehicles.As the core component in fuel cells,the ion exchange membrane has been a hot area of research in scientific research fields.On the other side,compare with the proton exchange membrane fuel cell,alkaline fuel cell does not need expensive platinum catalyst but also save the cost,so the research of anion exchange membrane is popular.In order to meet the requirement of fuel cell,anion exchange membranes(AEMs)have been expected to possess high ionic conductivity,low swelling,excellent mechanical,chemical and thermal stabilities.Therefore,in this study,a series of long side-chain polybenzimidazole membranes with high conductivity and chemical stability has been fabricated.And in order to futher improve its chemical stability,we changed the monomer of polybenzimidazole and synthesised aliphatic-aromatic polybenzimidazole,which explores the influence of main-chain to the performance of the membran including chemical stability.Firstly,a high molecular weight polybenzimidazole(PBI)was synthesized by 3,3',4,4'-Biphenyltetramine and 4,4'-oxybisbenzoicacid.Then,a long side-chain is grafted onto the PBI,resulting in a highly durable long side-chain polybenzimidazole AEMs(N-PBIs)successfully.The chemical structure of the PBI,side-chain(Sc)and N-PBI was characterized by FT-IR and 1H-NMR.The IEC of N-PBI samples are 0.83-1.36 mmol g-1 and the swelling ratios of these samples are 1.20-1.50%.Because the main chain and the side chain is hydrophobic and hydrophilic respectively,which is conducive to the formation of ion channels,so the electrical conductivity is better.The OH-conductivity of N-PBI increased from 0.040 to 0.11S/cm with the increase of temperature from 20 ? to 80?.The N-PBI membrane demonstrated highly alkaline stability in 1 M NaOH at 80? for over 1200 h.In order to explore the influence of the main chain of polybenzimidazole on the chemical stability and conductivity of anion exchange membrane,we sythesis three different PBI by 3,3'-Diaminobenzidine,1,7-heptanic diacid,4,4'-oxybisbenzoicacid and 1,10-sebacic acid.Then,a long side-chain is grafted onto these PBIs,resulting in a higher durable long side-chain polybenzimidazole.The electrical conductivity of these membranes increased to 0.08S/cm at 80 ?,the swelling ratios of these samples are 3.75-4.48% and the water uptake of these membranes are 15.5-18.2%.Finally those membranes demonstrated higher alkaline stability in 1 M NaOH at 80? for over 1500 h,and it still has a high ionic conductivity.
Keywords/Search Tags:Polybenzimidazole, fuel cell, ionic conductivity, anion exchange membranes, alkaline stability
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