Synthesis And Properties Branched Comb-shaped Poly(arylene Ether Sulfone)AEM

Fuel cells are considered to be a new generation of energy power systems due to their high energy density,high conversion efficiency,and low pollution.Alkaline anion exchange membrane fuel cell（AEMFC）combines the advantages of traditional alkaline fuel cells with proton exchange membrane fuel cells and can use non-precious metal catalysts.Anion exchange membrane（AEM）is one of the key components of AEMFC,and its performance directly affects the overall performance of the fuel cell.At present,there are two major challenges for anion exchange membrane materials:low ionic conductivity and poor alkaline stability.In recent years,various methods for improving the ionic conductivity and alkaline stability of AEMs have been reported,such as designed and synthesized comb-shaped polymers,block polymers,and crosslinked polymers.The imidazolium-functionalized poly（arylene ether sulfone）AEMs is considered one of good candidates due to its excellent thermal stability,mechanical properties,and easy structure-designing.However,the ionic conductivity and stability of the membrane material are not ideal in practical applications of fuel cells.We have found that branched structures can effectively improve the conductivity and chemical stability of proton exchange membrane materials.In addition,some studies confirm that the transport mechanism of the OH^-ions in the anion exchange membrane material and the transport mechanism of the H⁺in the proton exchange membrane material are similar.Therefore,in this work,we designed and synthesized branched imidazolium-functionalized poly（arylene ether sulfone）AEMs to solve low conductivity and poor stability.The specific research content and results are as follows:1)A series of branched comb-shaped poly（arylene ether sulfone）imidazolium-functionalized anion exchange membrane materials with a branching degree（0-8%）were prepared,and the effects of branching degree on the properties of the membrane were systematically investigated.The introduction of branched structure can significantly improve the conductivity and alkaline stability of the membrane.The membrane material with a branching degree of 8%exhibits the highest ionic conductivity(126 mS cm^-1)and alkaline stability（79%）.2)Poly（arylene ether sulfone）with a branching degree of 6%with different lengths of alkyl imidazolium side chain（4C,6C,8C,12C）were designed and synthesized.And the effect of the length of the alkyl imidazolium side chain on the properties of a branched AEM was systematically investigated.When the length of the alkyl side chain is 6 carbon atoms,the overall performance of the branched comb-type membrane material is more excellent.3)In order to further improve the conductivity and alkaline stability of the branched comb-shaped polymer membranes,we prepared block branched comb-shaped poly（arylene ether sulfone）copolymers.The B1 block branched membrane is that the hydrophilic segment is surrounded by a hydrophobic segment,which exhibits the best alkaline stability;the B2 block branched membrane is that hydrophobic segment is surrounded by a hydrophilic segment,where the membrane material exhibits the best ionic conductivity.In addition,both block membrane materials exhibit more excellent ionic conductivity and alkaline stability over to random branched membranes.