Preparation And Application Of Ionic Liquid Grafted Polyether Sulfone (PES)

Polyethersulfone（PES）has good thermal stability,excellent mechanical properties and chemical resistance,and was widely used in the preparation of various separation membranes.However,PES membranes generally had some problems such as low water flux,serious membrane fouling,and bacterial growth.Grafting hydrophilic monomers and antibacterial agents to the surface of PES membranes is a common method to improve the water flux,antifouling ability and antibacterial performance of PES membranes,but the reaction conditions were usually harsh and the reaction process was complicated.The bulk chemical modification of PES was also an effective way to prepare functional separation membranes.In this work,firstly,1-vinyl-3-butylimidazole tetrafluoroborate[IL（BF₄）]ionic liquid with high thermal stability,hydrophilicity and antibacterial properties was grafted onto the PES molecular chain by co-irradiation technology to prepare ionic liquid grafted PES（PES-g-IL）.Furthermore,the obtained PES-g-IL was used as a membrane material,and ultrafiltration membranes,nanofiber membranes and hollow fiber membranes were prepared by immersion precipitation phase inversion method,electrostatic spinning and dry-wet method respectively.Meanwhile,characterized the structure and performance of the membrane,and explored its application in water treatment,biomedicine and other fields.The main research of the paper is as follows:（1）Study on the compatibility of PES/IL（BF₄）blendsThe PES/IL（BF₄）blend was prepared by the solution blending method.Using Scanning Electron Microscope（SEM）,Thermogravimetric Analyzer（TGA）and Fourier Transform Infrared Spectrometer（FTIR）to systematically study its structure and performance.The results showed that IL（BF₄）and PES showed good compatibility;the benzene ring on PES and the imidazole ring on IL（BF₄）had a special interaction.（2）The grafting of IL（BF₄）to PES and the structure and properties of PES-g-IL（BF₄）The IL（BF₄）was successfully grafted onto the PES main chain by radiation grafting,and the PES-g-IL（BF₄）membrane material was obtained.Using nuclear magnetic resonance spectroscopy and weighing methods to study the grafting rate and grafting site,and determine the carbon atom（adjacent to the ether oxygen atom on the PES main chain）that is grafted onto the benzene ring after IL（BF₄）opens the double bond on.In addition,the hydrophilicity,antibacterial properties and thermal behavior of PES-g-IL（BF₄）materials with different grafting rates were further studied.The results show that the grafting of ionic liquids could improve the hydrophilicity of PES and endow PES with permanent antibacterial properties,which was expected to solve many industrial problems of PES as a separation membrane.（3）Study on preparation and performance of PES-g-IL（BF₄）porous membrane The PES-g-IL（BF₄）porous membrane was prepared by the immersion precipitation phase inversion method and compared with the unmodified PES porous membrane.Studies had shown that the PES-g-IL（BF₄）porous membrane had a more penetrating membrane pore structure and a higher porosity.In addition,the pure water flux and anti-fouling performance of the PES-g-IL（BF₄）porous membrane were significantly improved,and it had excellent antibacterial properties,the antibacterial rate against Escherichia coli and Staphylococcus aureus was above 99.99%.（4）Preparation of PES-g-IL（BF₄）nanofiber membrane and study on adsorption performanceA new type of ionic liquid IL（BF₄）grafted polyethersulfone（PES）nanofiber membrane was prepared by electrospinning,and the adsorption performance of the nanofiber membrane was studied.The results show that the adsorption capacity of PES-g-IL（BF₄）nanofiber membranes for anionic dyes（CR）and heavy metal ions（Cd（II））reached 120.3mg/g and 187.3mg/g,respectively,and could be recycled and reused.Meanwhile,according to adsorption kinetics and theoretical calculations,it was shown that the adsorption process of dyes and heavy metals by PES-g-IL（BF₄）nanofiber membrane was a spontaneous physical adsorption process,but it was controlled by multiple steps.In addition,the antibacterial test showed that the PES-g-IL（BF₄）nanofiber membrane had strong antibacterial ability.（5）Preparation of PES-g-IL（BF₄）hollow fiber membrane and its application in hemodialysisThe PES-g-IL（BF₄）hollow fiber membrane was prepared by the dry-wet method,and the morphology and structure of the PES-g-IL（BF₄）hollow fiber membrane was observed by SEM.The results showed that the grafted ionic liquid had higher porosity and better hydrophilicity than the ungrafted PES hollow fiber membrane.Further studies had found that PES-g-IL（BF₄）hollow fiber membranes could well remove toxins such as urea and lysozyme,and retain BSA protein;PES-g-IL（BF₄）hollow fiber membranes also showed a lower hemolysis rate and a lower degree of platelet adhesion,there was no platelet activation phenomenon;Meanwhile,PES-g-IL（BF₄）hollow fiber membrane coagulation time was slightly prolonged,which showed that it had better blood compatibility;In addition,the PES-g-IL（BF₄）hollow fiber membrane had low cytotoxicity to mouse fibroblasts,which meeted the standards of medical equipment.