Functional Modification And Performance Study Of Polyacrylonitrile Film Based On Click Chemistry

Polyaciylonitrile(PAN)could be prepared as membrane via non-solvent-induced phase inversion method because of its excellent chemical resistance and thermal stability,therefore,PAN has been regarded as one of popular membrane materials.Additionally,the caused severe membrane fouling and wetting in membrane filtration and contact applications respectively on account of the moderate contact angle of PAN membrane may suppress its separation properties and lifespan.In order to meet different membrane treatment applications,the PAN modifications in term of hydrophilicity and hydrophobicity have been a potential approach.Click chemistry has been extensively used in polymer synthesis and chemical modificaitions of organic membranes based on its simple operation,mild conditions and high conversion rate.In order to alleviate membrane problems of the low flux and poor anti-fouling,Tetrazole-functionalized polyacrylonitrile copolymers(TZ-PAN)were synthesized by cycloadditionreaction(click chemistry).The as-obtained TZ-PAN copolymers were further modified by N-arylation with methyl iodide to getmethylated tetrazole polyacrylonitrile(MTZ-PAN).The degree of functionalization(DF)was calculated by 1H NMR,ranging from 5%-16%,which could be controlled by reaction time(5min-120min),TZ-PAN and MTZ-PAN plat membranes were prepared and the test results showed the contact angle(CA)of TZ-PAN ultrafiltration membranes declined from 63° to 52°,the flux increased from 110L/(m2·h·bar)to 715L/(m2·h·bar)and enhanced recovery ratio(90%)after filtrating the 500ml BSA solution.After N-arylation reaction,the mechanical properties of UF membranes enhanced significantly,the elongation-at-break of MTZ-PAN-16 membrane attained 21%.Meanwhile,MTZ-PAN-16 membrane possessed increased contact angle,71°,decreased flux,242L/(m2·h·bar)and BSA retention ratio,80%.Theseresults indicated that click chemistry and ankylation reactions could tune effectively the hydrophilicity of PAN,which could improve the flux and anti-fouling properties of PAN membranes.In order to further investigate the effects of alkyl chain on PANmembrane properties,decane and hexadecane were introduced into TZ-PAN copolymers respectively via N-arylation reaction and DF were 10%and 20%.The modified PANmembranes had enhanced hydrophobic property and the contact of PANmembranes increased with the increase of DF and chain length of alkyl.When the DF was 20%,the CA of TZ-PAN-Decane and TZ-PAN-Hexadecane membranes were 101° and 104° respectively.The modified hydrophobic PAN membranes were applied to direct contact membrane distillation(DCMD)and the feed solution was 35g/L NaCl solution.The tests results indicated that with the increased temperature of feed solution(50-80?),the flux of TZ-PAN-hexadecane membranes increased from 3 kg/(m2·h)to 12kg/(m2·h),however,the separation factor was still below 1.Meanwhile,TZ-PAN-Decane and TZ-PAN-Hexadecane membranes had similar separation properties with the same DF.Therefore,alkyl chain definitely enhanced the hydrophobic property of PAN membranes,which could improve the operation effect.