Syntheses And Properties Of Non-covalent Crosslinked Anion Exchange Membranes

Nowadays,owing to the potential high energy efficiency and low cost,the scientific and industrial community pay more attention to anion exchange membrane fuel cells(AEMFC).As a key component of AEMFC,anion exchange membrane(AEM),largely determined the final performances of fuel cells.Because of low mobility of OH-,the AEM often suffers from low conductivity.In order to increase the conductivity of the AEM,the most facile method is to increase the ion carriers of the membrane.However,high ion-containing AEMs often suffer from higher water uptake,a higher swelling ratio and lower mechanical properties.Therefore,how to contruct an advanced AEM with balanced property among water uptake,ion conductivity and mechanical strength is of great important.Inspired to the development of supramolecular chemistry,in this dissertion,we introduce a secondary amide as a hydrogen-bonding crosslinking motif into the side chain of PPO backbone,and investigate the relationships between this non-covalent crosslinked structure and AEM pertinent properties.Thus,the following works have been carried out:(1)We design and synthesis a series of amide containing side chain tethered AEM from bromized PPO and functional tertiary amine bearing amide moiety by Menshutkin reaction.The amide hydrogen-based non-covanlent interaction in the AEM was confirmed by solubility test and variable temperature FT-IR techniques.Similar to traditional covalent crosslinked AEM,this non-covalent hydrogen based AEM exhibited good structural stability and thermal stability,such as moderate water absorption,suppressed swelling.In addition,with the merit of adaptability,this novel AEM based on non-covalent crosslinking could dissolve in hydrogen-interrupting solvent,such as DMF and NMP,which is a great challenge for traditional covalent crosslinked AEM.Meanwhile,PPO-SA with amide group showed good water holding capacity,especially at elevated temperatures,which ensured the AEM with high anion transportion efficiency and peak power density of sigle cell measurement(Pmax=122 mW/cm,55?).Also,with the presence of dynamic hydrogen bonding at the side group of PPO-SA,this membrane showed exceptional higher stretchability and flexibility(101%elongation at break),which is much higher than reported AEM with the elongation at break less than 30%.(2)With the aim of increased the non-covalent crosslinking density,we further synthesized a novel tertiary amine containing two amide moieties,acting as the side chain of comb-shaped AEM(PPO-DA).As the increase the content of amide-bearing side chains,the less solubility of PPO-DA with the order of PPO-DA0.2>PPO-DA0.3>PPO-DA0.4.Compared with the PPO-SA with single amide moiety,PPO-DA containing two amide-moieties showed higher dimensional stability and tensile strength.At the dry state(25?,RH<25%),the tensile trength of PPO-DA0.3 and PPO-DA0.4 were higher than 60 MPa,which is two times higher than PPO-SA.By introducing a secondary amide as a hydrogen-bonding crosslinking motif,the resulting AEM exhibits high mechanical strength and excellent flexibility,suppressed water uptake,enhanced thermal stability,comparable ion conductivity and good fuel cell performances,as well as good solubility,which is a great challenge for traditional covalent crosslinked AEM.More importantly,such a novel supramolecular strategy offer us a new toolbox to improve the comprehensive properties of AEMs.