Syntheses And Morphology Regulation Of Poly(arylene Alkylene)-based Anion Exchange Membranes

Anion exchange membrane（AEM）is an important component of electrochemical equipment operating in alkaline media.It requires high conductivity,excellent mechanical properties,good alkaline and oxidation stability.A series of anion exchange membranes without ether bond in main chain were prepared for good alkaline stability,on this basis by constantly constructing phase separation structure and fixing the phase structure through UV crosslinking,so that the membrane has good alkaline stability,and at the same time optimize its other properties.（1）A poly（quinquephenylene-co-diphenylene）ionomer（PQDP）was prepared by coupling polymerization of 4,4-bis（4-chlorophenyl）-1-methylpiperidine monomer and quinquephenylene monomer.This ionomer not only makes polyphenylene as rigid backbone,but also introduces piperidine cation with good stability into the ionomer.The conductivity did not decrease after soaking in 1M Na OH at 80°C for 30 days.Also,the residual mass retention rate is still above 95%after in Fenton reagent for 5 h.In addition,PQDP membrane has excellent mechanical properties,such as high Young’s modulus（1 GPa）and tensile strength（40 MPa）.The heteroatom free polymer backbone and high content of phenylenes are considered to be the main factors for the excellent chemical stability and mechanical properties of PQDP.Meanwhile,the conductivity of PQDP membrane is also high,which is up to 73 m S/cm（90°C）.The maximum power density of H₂-O₂ fuel cell assembled with PQDP-3 is up to 507 m W/cm²,showing excellent single-cell performance.（2）The poly（arylene alkylene）was prepared by condensation polymerization,and then the hydrophilic side chain and the superhydrophobic fluorocarbon side chain were introduced into the polymer.By increasing the thermodynamic incompatibility between the side chains,the microphase separation structure of the membrane is effectively constructed.AEMs,containing fluorocarbon side chain,has better microphase separation structure,which was characterized by SAXS.These suggests that the hydrophilicity of side chain is of the importance in the formation of the aggregation structures and ion clusters.At the same time,the membrane with better microphase separation structure can effectively inhibit water absorption and improve conductivity,so as to obtain higher dimensional stability.For example,compared with the PBPA-1QA,the Cl^―conductivity at 30℃ of PBPA-Me7F3QA（the same IEC）is increased by about 70%（19.5 m S/cm）,and has the higher ion diffusion coefficient,for example,the ionic diffusion coefficient of PBPA-FB7F3QA was 3.7×10^-6 cm²/s.（3）The membranes（PBPA-Me7F3QA）,has good micro phase separation structure,were immersing in 5 mg/m L of DAS in aqueous solution,using the better electrostatic interaction between DAS and cationic of membrane.After DAS adsorption on the surface of membrane,UV irradiation can cause crosslinking structure in the membrane surface.Due to the DAS adsorbed around the cation in the hydrophile surface of the membrane,the azide group generates nitrogen bin under UV irradiation,and then its addition or insertion reaction will take place with adjacent groups（phenyl,methylene,quaternary ammonium）.Therefore,the microphase separation structure is effectively fixed in the cross-linking process without destroying its phase morphology.