Preparation Of Poly(ionic Liquid)s Based Photothermal Conversion Materials And Their Solar Interfacial Evaporation Properties

Water is the source of life on which human beings depend for survival and development.It is also the basic and precious natural resource for the sustainable development of human society,and it is an important strategic resource for national economic development.The total amount of fresh water in China is small,and the efficient and economical use of solar evaporation technology to obtain clean water is of great significance for alleviating the shortage of fresh water resources and maintaining the sustainable development of society and economy.It has attracted extensive attention of researchers and become one of the research hotspots in the academic circle.In recent years,with the development of solar energy photothermal evaporation technology and the rapid development of nano materials in the field of photothermal conversion.New technology of solar driven interface photothermal water evaporation is proposed by science and technology workers.This technology locates the heat generated by solar radiation on the surface of the material,which makes the process occur in the solar-thermal conversion materials on the surface of the thin layer of air/water interface,so as to minimize the heat loss and improve the efficiency of the conversion.The photothermal conversion efficiency of solar driven interface evaporation device mainly depends on the synergy effect of key factors such as the material's light absorption,pore structure,thermal insulation performance and water transmission.In terms of the essence of photothermal conversion,the evaporation efficiency,photothermal conversion performance and salt resistance of materials depend largely on the physicochemical properties of photothermal materials.Therefore,the development of new and high-performance photothermal materials is still a research hotspot in this field.In addition,the solar driven interface evaporation device is prone to salt precipitation and aggregation in the water solution with high salinity,resulting in the decrease of the light heat conversion efficiency.Therefore,the salt resistance of the interface evaporation device needs to be further improved.In view of the deficiency in the research field of photothermal materials for solar driven interfacial evaporation,the research content of this paper focuses on the design,synthesis,photothermal vapor conversion efficiency and salt resistance of bulk poly(ionic liquid)s porous materials.Ionic liquid monomers with different functional groups are selected to prepare bulk porous poly(ionic liquid)s materials by polymerization and cross-linking.The photothermal vapor conversion efficiency and salt resistance of poly(ionic liquid)s materials are tested,and the main factors affecting the efficiency of solar driven evaporation system and the mechanism of salt tolerance are discussed.The main contents and conclusions of this paper are as follows:(1)The white bulk poly(ionic liquid)s PDVB-BF4ILs were synthesized by solvothermal reaction of 1-vinyl-3-ethylimidazolium tetrafluoroborate([VEIM][BF4],monomer),divinylbenzene(DVB,crosslinking agen),azobisisobutyronitrile(AIBN,initiator),using tetrahydrofuran and water as mixed solvent.The energy conversion efficiency of the Janus C-PDVB-BF4ILs was calculated to be 92.4%under 1 kW m-2 solar illumination,and show good salt resistance to 20 wt%NaCl solution.(2)The poly(ionic liquid)s gels PMBA-BrILs were obtained by the polymerization reaction of 1-vinyl-3-ethylimidazolium bromide([VEIm]Br,monomer),N,N'-methylene-bis-acrylamide(MBA,crosslinking agent)and Ammonium persulfate(APS,initiator),using distilled water as solvent.The PPy-PMBA-BrILs were prepared by in situ polymerization of pyrrole on the surface of PMBA-BrILs with spraying method.Then,the co-modified Ag/PPy-PMBA-BrILs was obainted by spraying AgNO3 and NaBH4 onto the upper surface of the PPy-PMBA-BrILs alternately.The photothermal conversion efficiency of Ag/PPy-PMBA-BRILs that co-modified by polypyrrole and Ag particles was calculated to be 88.7%,and exhibited a remarkable desalination effect on artificial seawater with a total salinity of 3.5wt%.(3)The faint yellow poly(ionic liquid)s gels SiO2-PILs were obtained by the polymerization reaction of 1-vinyl-3-ethylimidazolium bromide and acrylamide([VEIm]Br and AM,monomers),N,N'-methylene-bis-acrylamide(MBA,crosslinking agent),Ammonium persulfate(APS,initiator)and hydrophobic SiO2 hollow microspheres,using distilled water as solvent.The poly(ionic liquid)s gels Ag/PPy-SiO2-PILs,which co-modified by polypyrrole and Ag particle was prepared by in-situ polymerization of black polypyrrole and reduction of Ag particles on the surface of SiO2-PILs.The photothermal conversion efficiency of Ag/PPy-PILs and Ag/PPy-SiO2-PILs was calculated to be 88.4%and 90.5%,respectively.Meanwhile,it showed excellent salt tolerance to simulated seawater and different concentrations of NaCl solution.(4)The hypercrosslinked polymers composites C-[BzMim]C1-co-PhH and C-[BzPy]Br-co-PhH were obtained via facile Friedel-Crafts alkylation of 1-benzyl-3-methylimidazolium chloride([BzMim]Cl)or N-benzylpyridinium bromide([BzPy]Br)and benzene(PhH)as monomers,formaldehyde dimethyl acetal(FDA,cross-linker),using 1,2-Dichloroethane(DCE)as solvent,a moderate amount of carbon black,and promoted by anhydrous ferric chloride(FeCl3).The photothermal conversion efficiency of C-[BzMim]Cl-co-PhH and C-[BzPy]Br-co-PhH was calculated to be 85.2%and 88.4%,respectively.Meanwhile,they showed excellent salt tolerance to different concentrations of NaCl solution.