Modification Of Polyethersulfone By Ionic Liquids And Its Application

Polyether sulfone（PES）has been used in many fields because of its excellent heat resistance,chemical corrosion resistance,hydrolysis resistance and excellent mechanical properties.Ionic liquids（ILs）are room temperature molten salts composed of anions and cations,which have antibacterial,ionic conductivity,hydrophilicity and other properties.Therefore,the ILs have been extensively used in polymer modification in recent years.In this work,PES/ionic liquid（1-vinyl-3-butyl imidazolium tetrafluoroborate,IL）blends and IL grafted PES（PES-g-IL）were prepared by the method of“melt blending-irradiation grafting”.The phase behavior and physical properties of PES/IL blends and PES-g-IL systems were systematically studied.The potential applications of the prepared PES-g-IL in uranium extraction from seawater and triboelectric nanogenerator were explored.The main contents are as follows:（1）Phase separation behavior and properties of PES/IL blends:The compatibility and interaction between PES and IL were systematically studied by SEM,DSC,FTIR and NMR.The results show that the sulfone group on PES can have hydrogen bonding with hydrogen on the ionic liquid imidazole ring,so PES has good compatibility with IL.The phase separation behavior of PES/IL blends during heating process was traced by SAXS.The results show that the PES/IL blends exhibit typical lower critical solution temperature（LCST）phase behavior.It was found that the physical properties such as hydrophilicity and conductivity of PES/IL blends strongly depend on the phase structure of the blend.The contact angle of neat PES is 89.5°,and its surface resistance（Rs）of the sheet is greater than 10¹³Ω/sq.The contact angle of homogeneous PES/IL=70/30 is 68.9°,and its order of Rs decreases to 10⁹Ω/sq.After phase separation,the contact angle of PES/IL=70/30 further decreased to 61.4°,and the order of Rs was increased to 10¹¹Ω/sq.（2）Study on the phase separation behavior and properties of IL grafted PES:The homogeneous PES/IL blends were irradiated withγrays,so that IL was grafted on the main chain of PES.NMR was used to confirm that IL was grafted on the carbon atom of benzene ring linked to ether bond.The phase separation behavior of PES-g-IL was studied by SEM and SAXS,and the LCST phase behavior and SD phase separation mechanism was revealed.Compared with PES/IL blend,PES-g-IL shows lower phase separation temperature.In addition,the hydrophilicity and conductivity of each PES-g-IL sample before and after phase separation were further studied.The results show that the contact angle of PES-g-IL=70/30 decreased to 63.2°,and the order of Rs decreased to 10¹⁰Ω/sq.After phase separation,the hydrophilicity of PES-g-IL was further improved,with a contact angle of 58.9°,while the Rs increased by two orders of magnitude.（3）Application of PES-g-IL nanofiber membrane in uranium extraction from seawater:PES-g-IL nanofiber membranes were prepared by electrospinning technology.Through the adsorption experiment simulating seawater,the adsorption of uranium by nanofiber membranes with different IL grafting rates was explored under different initial concentrations,different adsorption times and the coexistence of multiple competing ions.The results show that PES-g-IL nanofiber membrane had good selective adsorption for uranium.The adsorption mechanism was explored using surface Zeta potential,FTIR and XPS.It was found that the PES-g-IL nanofiber membranes adsorbed uranium through metal complexation.In addition,the repeatability tests of nanofiber membrane were carried out,and it was found that the PES-g-IL nanofiber membrane as an adsorption material still has an adsorption effect on uranium after multiple adsorption-desorption cycles.（4）Application of IL modified PES membrane material in triboelectric nanogenerator:The friction nano electricity generation behavior of IL modified PES materials was systematically studied,and the effects of physical addition and chemical grafting,different membrane morphologies,and friction frequencies on the output performance of triboelectric nanogenerator（TENG）were discussed.The results show that the amount of IL addition/grafting ratio had a significant effect on the output electrical signal and dielectric properties:the open circuit voltage and short circuit current of PES/IL=80/20 sheet was 10.8 V and 1.4μA,respectively,which were 3 times and 2 times that of neat PES sheet（3.6 V,0.7μA）.At 1 Hz frequency,the dielectric constant and dielectric loss of PES/IL=80/20 sheet was 11.6 and 0.9,respectively,while the dielectric constant and dielectric loss of neat PES were 0.3 and 0.3,respectively.Compared to physical addition,these parameters of the chemical grafted samples will be reduced to a certain extent:the open circuit voltage of the PES-g-IL=80/20 sheet was 9.2 V,the dielectric constant was 7.6,and the dielectric loss was 0.4,which was caused by the grafting fixation of cations limiting the movement of anion and cation of IL.In addition,due to the large specific surface area of nanofiber membranes,the open circuit voltage and short circuit current of PES-g-IL=80/20 nanofiber membranes were11.5 V and 1.5μA,respectively.