Preparation And Performance Study Of Porous Polyionic Liquid Materials Based On High Internal Phase Emulsion Template Method

Poly(ionic liquid)s(PILs)are a type of polyelectrolyte in which repeat monomer units carry various anionic and cationic species of ILs.PILs materials,acted as a new type of polymers,combine unique properties of ionic liquids with macromolecular architecture of polymers,such as high ionic conductivity,good chemical stability,compatibility,and processability.PILs materials have been attracted widespread attention in separation science,catalysis,biomedicine,electrochemistry and others.Importantly,hierarchically porous PILs materials have received tremendous attention owing to their large specific surface areas,high porosity and abundant pore structures,which are beneficial to transport and mass transfer of functional materials.Up to now,many synthetic methods for porous PILs materials have been reported,such as emulsion template,hard template,electrostatic complexation and so on.Compared with other methods,emulsion template method has various advantages for preparation of porous PILs material,e.g.,convenient operation,low cost,and scale-up preparation.In particular,the HIPEs(greater than 74%of volume fraction of dispersed phase)containing polymerizable monomer in the continuous phase exhibit the stable solid-like rheological properties,which makes HIPEs become an efficient template for porous monolith materials.Emulsion is not a thermodynamical system,the key to application of emulsion template is stability and controllability of oil-water interface,not only determine whether the material can be successfully prepared or not,but also affect directly the pore structure characteristics and adjustability of the porous materials.Previous reports of PILs monolithic materials by the HIPEs template method are rare,and the majority of relative research were focused on the emulsion system with CO2 acted as one phase.Although the purification of the materials based on emulsion including CO2 phase is simple,the preparation process of emulsions is very harsh and not easy to control.At the same time,the appropriate polymerizable ionic liquid monomers in CO2-emuslion are rare and very limited.Therefore,it is very necessary to develop a controllable approach for emulsion-templated preparation of PILs materials.In a given case,the stabilizer is important for controlling interface properties of emulsion system.Thus,it is essential to design a novel stabilizer for constructing stable interfacial film,which is beneficial to obtain a stable emulsion.It has lays a good foundation for the preparation of porous PILs by the emulsion template method.Base on the research background mentioned above,HIPEs template method is developed for preparation of hierarchical porous PILs materials.By designing and synthesizing a novel special stabilizers,which can form the stable interfacial film and then to resist emulsion instability caused by micro-environmental changes in the emulsion droplets during the preparation of PILs materials,and finally achieving the hierarchical porous PILs monoliths.Studies found that the as-prepared PILs monolithic materials have high porosities and good thermal stability,and efficient adsorption of PM2.5 in the polluted air.Furthermore,the composite PILs material containing highly dispersed Au nanoparticles is obtained through a simple anion exchange method followed by reduction reaction.The as-prepared Au/PILs composite material exhibits good catalytic activity.Specifically,the major work was done in the following two aspects:In the first part of the thesis,we devoted to design and synthesize a polymerable zwitterionic compound containing cholesterol group.The as-synthesized stabilizer is capable of preparing the stably high internal phase emulsions,which can be used the template for production of the hierarchical porous PILs monoliths with interconnected network structures based on emulsion templated method.Firstly,a series of O/W HIPEs were formed via one-step homogenization of polymerizable ILs([AEIM]Cl,[AVIM]Cl,[VBTMA]Cl)and n-heptane solution containing a specially designed stabilizer.It is shown that the behaviors and stability of as-prepared emulsions are able to adjust via the change of stabilizer concentrations,types and the concentration of ionic liquid.The as-synthesized stabilizer is crucial to stabilize the emulsion system,which can effectively reduce the interfacial tension between the oil and water interface.Moreover,rheological studies has shown that HIPEs have good mechanical stability,viscoelasticity,and recovery.Thereby,a series of hierarchical porous PILs monoliths were obtained after the reaction in external phase by free radical polymerization.The as-synthesized stabilizer can form the super-stable interfacial film at the O/W interface,this interface film can be used to resist demulsification in emulsion caused by the changes of micro-environment during polymerization.Then,porous PILs monoliths with interconnected network structures were successfully preparation.In addition,SEM measurements suggested that the PILs monoliths have open pore structure,which can be controlled by the change of the initial emulsion formulation.XPS measurements confirmed that the stabilizer is successfully copolymerized onto the skeleton of the PILs monoliths,which not only modified the surface properties,but also simplified the purification process.Furthermore,the PM2.5 capture measurement was performed in a closed and static system,which mimicked the static polluted atmosphere.As a result,the as-synthesized porous PILs monolith exhibited excellent performance in PM2.5 adsorption(1582.94 mg/g).This can be attributed to the porous structure(i.e.,improved adsorption sites),and plenty of electrically charged sites in PILs monoliths,which can enhanced electrostatic binding of PM2.5 on the PILs monoliths surface.In the second part of the thesis,the composite Au/Poly[AVIM]Cl materials were prepared based on the first work.The approach involves anion-exchange followed by the reduction of Au ions.TEM measurements demonstrated that the Au NPs were uniform and homogenously dispersed on the framework of Poly[AVIM]Cl,and the average size of Au NPs was 2.92 nm.At the same time,HR-TEM measurements showed that the presence of a high resolution lattice.It is known that the introductionof Au NPs had no obvious effect on the macroscopic morphology and microstructure of porous PILs via FE-SEM analyses.XPS tests demonstrated that there is Au+ in the Poly[AVIM]Cl framework beside Au0.AAS measuements found that,the loading content of Au NPs was 4.5%.Based on this,Au/Poly[AVIM]Cl was used as a heterogeneous catalyst to show a good catalytic effect in the reduction of p-nitrophenol(4-NP)to p-aminophenol(4-AP).Thus,this work have provided a facile and effective method for the preparation of the composite PILs materials loading with metal NPs,and lays the foundation for the formation of high-performance catalysts.