Research And Application Of Gels/Anion Conducting Membranes Based On Functional Ionic Liquids

As a kind of materials with unique physical and chemical properties,ionic liquids have attracted extensive attentions.In earlier studies,ionic liquids were mainly considered as green solvents due to their low volatility and non-flammability.The diversity and adjustable characteristics of ionic liquids greatly expand their application fields.The physical and chemical properties of ionic liquids can be customized by modulating the structures of cations and anions.In other words,functional ionic liquids aiming at specific applications can be designed and synthesized,which is also one of the main reasons why ionic liquids are popular in various fields.In recent years,due to the flexible and designable structures of ionic liquids,the preparation of advanced materials based on functional ionic liquids has become a hotspot.On the one hand,the various ordered self-assembled aggregates formed by the modified and functionalized ionic liquids can be utilized to construct supramolecular gels and other functional soft materials.On the other hand,we can introduce ordered self-assembled aggregates into anion conducting membranes to construct ordered and well-defined ion transporting channels,significantly expanding the application of ionic liquids and ordered aggregates.As an important derivative of ionic liquids,poly(ionic liquid)s have almost all the characteristics of ionic liquids and meet the needs of practical applications.The ionic conductivity,electrochemical and thermal stability of poly(ionic liquid)s have made them show broad application prospects in the field of electrochemistry.In this dissertation,based on the designability and functional modification of ionic liquids,a series of ionic liquids and poly(ionic liquid)s with specific functions were designed and synthesized.The research work was mainly divided into the following five parts:1.We synthesized a polymerized imidazolium-type zwitterionic salt(ZIW),and dissolved it in an ionic liquid to prepare a two-component mechanically strong ionogel by in-situ photopolymerization.The zwitterionic groups in zwitterionic polymer scaffold have strong dipole-dipole interaction between each other,and ion-dipole interaction with the ions of ionic liquid solvent,resulting in the formation of physical crosslinking.The ionogel exhibits superior mechanical strength without any crosslinker,which is comparable to that of chemical crosslinked ionogels.In addition,the ionogel also presents good self-healing ability,electrochemical stability and mechanical flexibility,showing great application potential in flexible devices.2.A homogenous,optically transparent,and photochromic supramolecular hydrogel was prepared via the co-assembly of zwitterionic amphiphile(3-(1-hexadecyl-3-imidazolio)propanesulfonate,C16IPS)and ammonium heptamolybdate(Mo7).In zwitterions,the cations and anions are covalently connected.Thus,there is a delicate balance of electrostatic attraction and electrostatic repulsion between C16IPS and anionic Mo7 clusters,which promotes the formation of optically transparent hydrogel.The gel behavior,inside morphologies,rheological properties and photochromic properties were studied in detail.Supramolecular hydrogels are composed of highly ordered spherical micelles or aligned wormlike micelles.By tuning the concentration of C16IPS and the molar ratio of C16IPS/Mo7,the mechanical strength and photochromic ability of hydrogels can be adjusted.In particular,supramolecular hydrogels exhibit significantly enhanced photochromic ability compared with the pure Mo7 aqueous solutions with the same Mo7 concentration,showing great applied potential in the repeatable information recording and storage.3.We designed and synthesized a polymerizable ionic liquid with carboxylic group(VmimCM),and copolymerized it with a monomer of thermal-sensitive polymer(PNIPAM)to construct the primary skeleton of the hydrogel.A dual crosslinked hydrogel was prepared after the physical crosslinking of iron ions and carboxyl groups.The mechanical strength and conductivity of hydrogels were significantly improved by introducing the dual crosslinked poly(ionic liquid)network.The excellent thermal-sensitivity of PNIPAM and the good conductive property of poly(ionic liquid)provide the hydrogel with an attractive performance as a thermal-responsive switch.In addition,the dual crosslinked hydrogel also exhibits good redox responsiveness based on the different oxidation states of iron ions.4.A double network hydrogel was constructed based on the chemically crosslinked polyelectrolyte network(poly(2-acrylamide-2-methyl propanesulfonic acid),PAMPS)and interpenetrating methyl cellulose(MC).After introducing concentrated alkaline solution(KOH),the PAMPS-K/MC hydrogel exhibits extremely improved ionic conductivity(up to 105 mS·cm-1 at room temperature).In addition,the freezing point of PAMPS-K/MC hydrogel can be reduced to about-30?,indicating the hydrogel possesses excellent antifreezing properties.The hydrogel retains acceptable ionic conductivity and mechanical properties even at-20?.The flexible zinc-air battery with PAMPS-K/MC alkaline hydrogel as the electrolyte exhibits good electrochemical performance,mechanical flexibility,and still has competitive specific capacity and energy density even at-20?.5.Anion conducting membranes with different nanostructures were prepared by in-situ photopolymerization of the LC samples formed from the self-assembly of polymerizable and amphiphilic ionic liquids.Then,the comprehensive properties of membranes were investigated in detail:(1)The LDHs hybrid anion conducting membrane preserved liquid crystalline morphology was constructed.LDHs was synthesized by in-situ coprecipitation using the hexagonal liquid crystal phase as nanoreactor.The results of SEM and TEM measurements reveal that the hexagonal LC phase directed the formation of hierarchical structures of LDHs.In addition,IEC,water uptake,swelling degree,hydroxide conductivity,alkaline stability and mechanical property of LDH hybrid membranes have been characterized,and compared with the anion conducting membrane without LDHs.The LDHs hybrid membranes exhibit higher ionic conductivity,better alkaline stability and mechanical strength,and superior electrochemical performance in the zinc-air battery.(2)The first example of liquid-crystalline anion exchange membrane preserving inverse Ia3d bicontinuous cubic structure(AEM-Ia3d)was prepared.Compared to the anion exchange membranes with hexagonal and lamellar liquid crystalline nanostructures,AEM-Ia3d shows significantly increased hydroxide conductivity,excellent water management and mechanical performance.The AEM preserving the 3D interconnected nanochannels of the bicontinuous cubic structure can selectively transport hydroxide via a reduced migration barrier,while inhibiting the crossover of hydrated ions and organic solutes(Zn(OH)42-and alcohols).In addition to the size-based exclusion mechanism,the tortuosity of 3D interconnected ion channels also contributes to the permselectivity between the hopping and diffusing ions.