Preparation Of Pyridine-type Anti-swelling BPPO Anion Exchange Membrane

It's very important for anion exchange membranes to have a high permselectivity?low membrane area resistance?low sweling ratio and high ion exchange capacity,etc.At present,cation exchange membrane can basically meet the demand of application,for example Nafion membrane produced by DuPont,but the anion exchange membrane is still faced with some problems in large-scale application and improvement of performance.Traditionally,the preparation of AEMs is usualy based on the post-modification of pristine polymers,then using trimethylamine aqueous solution for quaternization reagent.This method has several disadvantages like the quality of the membrane is not enough stable and membranes have a loose and rough morphology due to the erosion of trimethylamine(TMA),which affect the membrane performance.And the application of AEMs has been limited due to the trade-off effect between ion exchange capacity and water uptake.Cross-linking has been widely used for preparing AEMs with improved dimensional stability.Furthermore,the method also exists some problems.Such as the experiment process is complex;the cross-linker may not be compatible with the polymer chains,which can cause a poor quality of the membrane and it's difficult to control the degree of cross-linking to avoid undesired gelation.Our work is aimed to develop an excelent performance AEMs with low water uptake,high ion exchange capacity and simple experimental process,which can demand the need for industrialization application.The specific studies are shown as follows:(1)An AEM was prepared through internal cross-linking networks in a poly(2,6-dimethyl-1,4-phenyleneoxide)(BPPO)without heating via a nucleophilic substitution reaction of bromide groups and bipyridine groups.Therefore,the effect of crosslinking on properties such as IEC,water uptake,sweling ratio,mechanical strength,the degree of crosslinking,thermal stability and desalination efficiency were studied via controlling the degree of the membranes.The experimental results showed that the cross-linked BPPO-20 membrane exhibits proper water uptake,excelent dimensional stability and desalination efficiency.(2)The properties of anion exchange membrane were investigated by using single pyridine as quaternization reagent.Pyridine group has a large ion volume and is hydrophilic,which can effectively control the swelling property of the membranes.In the experiment,the length of the hydrophobic alkyl chain was changed by choosing different quaternary ammonium reagents.The performance of the anion exchange membranes with different length of alkyl chain has been researched.It was proved that increase the chain of alkyl on quaternary ammonium group can effectively control the water uptake.