Studies On Preparation And Application Of Polymer Composite Interfaces With Ionic Liquid Superwettability

Ionic liquids?ILs?with unique physical and chemical properties,such as high thermal and chemical stability,low vapor pressure,have been widely used in catalysis,separation,electrochemistry and materials science in recent years.A key issue during ILs used in these areas is the wetting behaviors of ILs at the interfaces.For example,studies of solid surfaces with superwettability by ILs can effectively improve the catalytic separation efficiency,optimize the electrochemical processes,improve the performance of IL-related interfacial materials and guide the design of new high-performance materials.However,the studies of ILs wettability is still in its infancy,and more other researches are urgenly needed,such as realizing responsive superwettability of ILs,improving the separation performance of ILs,and preparing high-performance IL-related materials.In this thesis,we prepared a series of polymer composite interfaces with IL superwettability?PCIIS?.The chemical compositions of the PCIIS were characterized by X-ray photoelectron spectroscopy?XPS?.The surface morphologies of the PCIIS were observed by atomic force microscopy?AFM?and scanning electron microscopy?SEM?.We mainly studied the PCIIS used as temperature-responsive interface to intelligently control superwetting behavior of IL,superwetting separation membranes to separate ILs and water,and high-performance ionogel/metal composite flexible transparent electrodes.The detailed research contents and the results are as follows:1.The IL 1-ethyl-3-methylimidazolium bis?trifluoromethylsulfonyl?imide?[EMIM][NTf₂]?thermal responsive polymer poly?phenylethyl methacrylate??PPhEtMA?and superILphobic1H,1H,2H,2H-perfluorodecyl trimethoxysilane?PFDMS?mixed brushes-modified binary polymer composite interface?BPCI?was prepared via surface mixed silane coupling agent modification and subsequent surface-initiated atom transfer radical polymerization.By regulating the molar ratios of PPhEtMA to PFDMS,chemical compositions of the polymer molecules and roughness of the silicon wafer surface,the BPCI can realize temperature-responsive IL superwettability.At low temperature of 20?,the BPCI is superILphilic with an[EMIM][NTf₂]contact angle of 10.0±0.5°.When elevating the temperature to 100°C,the BPCI become ILphobic,contact angle on the BPCI incrasing to 127.8±1.8°.The specific response temperature of the BPCI is 60-70?,and the BPCI can reversibly switch between superILphilicity and ILphobicity for several cycles when repeatedly changing the surrounding temperature between 20°C and 100°C.¹H NMR and quartz crystal microbalance results demonstrate that the wettability changes result from a temperature-dominated cation–?interaction between[EMIM][NTf₂]and PPhEtMA/PFDMS mixed molecular brushes.2.IL-passed-through superwetting separation membranes were prepared by chemical modification of porous stainless steel membranes with ILphlic polymer networks.The superwetting separation membranes are superILphilic under water and superhydrophobic under IL,and can efficiently separate IL from IL/water mixture with IL selectively passing through.The separation efficiency can reach up to 98%with relative high flux(in the range of 500-2000 L M^-3 h^-1).Our IL-passed-through superwetting separation membranes can also efficiently separate different ILs/water mixtures.We investigated the effect of membrane pore size on separation performance and found that decreasing pore size leads to increased separation efficiency and decreased flux.We explained the separation mechanism by comparing the interface energies and adsorption energies between superwetting separation membranes with ILs and water.3.To further improve the separation flux,we prepared water-passed-through superwetting separation membranes via chemical modification of porous stainless steel membranes with hydrophlic polymer networks.The hydrophlic polymer networks can selectively absorb water and lock water forming porous hydrogel membranes,which are superhydrophilic under IL and superILphobic under water.These superwetting porous hydrogel membranes can efficiently separate water from the IL/water mixture with high separation efficiency?>98%?and ultra high flux(up to45000 L M^-2 h^-1)due to the much smaller viscosity of water than IL.The water-passed-through superwetting separation membranes can also efficiently separate various ILs/water mixtures and keep self-cleaning.We investgated the effect of chemical composition and membrane pore size on the separation performance.It shows that stronger hydrophilicity of the polymers results in higher separation efficiency and higher separation flux,and decreasing pore size leads to increased separation efficiency and decreased flux.We explained the separation mechanism by dynamically monitoring the substitution processes between IL and water,and comparing the interfacial energies and adsorption energies of ILs and water with the separation membrane.By combining the IL-passed-through superwetting separation membrane in the above work with the water-passed-through superwetting separation membrane,we can realize the continuous separation and purification of ILs simultaneously.4.In the above three works,The PCIIS are constructed by controlling the superwetting behaviors of ILs on the polymer composite interfaces.In this work,we prepared high-performance ionogel/copper?Cu?grid composite flexible transparent electrodes?ionogel/CuG FTEs?by constructing IL?[VEIM][NTf₂]?-superwettable Cu layer and subsequent in situ cross-linked polymerization of[VEIM][NTf₂].We use two ways?inkjet printing and photolithography?to patterned silver seeds and then electroless deposition of Cu to construct Cu grids with different sizes.The Cu deposition time,chemical compositions of ionogels and size of Cu grid were optimized to achive ionogel/CuG FTEs with high performance.The as-prepared ionogel/CuG FTE exhibits a sheet resistance of 10.9?sq^-1 and optical transmittance of 90%at 550 nm.Introduction of the thin uniform P[VEIM][NTf₂]ionogel nanofilm by virtue of the superwettability of the Cu layer endows the electrode with excellent mechanical flexibility and stability.This new high-performance ionogel/CuG FTE has a promising prospect in touch screen.