Preparation Of Hydrophobic Porous Polyionic Liquid Material By HIPE Template Method And Study Of Its Properties

Porous poly(ionic liquids)(PILs),an emerging class of ionic porous materials,combine the characteristics of ionic liquids,polymers and porous materials with ion exchange,high charge density,high porosity and processability,which can be used in many fields such as carbon materials,adsorption and separation,catalysis and smart response materials.Owing to the intrinsically charged character within their pores,porous PILs can alter their physicochemical properties much more broadly and easily than other porous polymers by ion-exchange.Obviously,porous PILs materials have greater applicability and are advantageous in a variety of applications.The high internal phase emulsion(HIPE)template method is a very important method for preparing porous materials.HIPE are a class of emulsions with a dispersed phase volume greater than 74%,which are usually polymerized in continuous phase to obtain highly porous materials(PolyHIPE).To date,to prepare the PolyHIPE material the monomers used are mainly electrically neutral monomers,such as styrene,methacrylic acid,methacrylamide,etc.,and there are few reports of ionic liquid monomers.In only a few reports,HIPE prepared by using supercritical CO2 as the dispersed phase are employed as templates to prepare porous materials.Although the removal of dispersed phase is relatively easy,the formation of emulsion requires special equipment and harsh experimental conditions,especially synthesis of special fluorine surfactant.In other work,the hydrophilic porous PILs materials prepared by the O/W HIPE template,but the materials release a large amount of organic solvent during the drying process,which not only increase the material preparation cost but also bring environmental pollution.Therefore,it is necessary to develop a simple,green and economical HIPE template method for the preparaing porous PILs.Meanwhile,there are some key factors need be concerned,such as,choice of a suitable stabilizers,precisely control the pore structure,green process for reducing organic solvents.Based on the above research background and our group long-term research experiences on liquid-liquid stable interface,in my thesis work a series of porous PILs with adjustable internal structure were prepared by the W/O HIPE stabilized by cholesterol derivatives.Most importantly,in my thesis work the HIPE does not contain organic solvents that do not participate in the reaction,so the release of organic solvents is reduced during the preparation of the material,which meets the requirements of current green chemistry.Meanwhile,the experimental results show that the Porous PILs prepared in this work can not only be used as an effective precursor for the preparation of porous carbon materials,but also as a high-efficiency adsorbent for anionic dyes in organic solvents.This thesis work includes two aspects:The first part of the work,we have successfully prepared a hydrophobic polyionic liquid monoliths with a porous structure through the W/O HIPE template method.Firstly,a series of W/O HIPE with different chemical compositions were prepared by using(l-allyl-3-vinylimidazolium bis(trifluoromethanexyl)imide salt)as a monomer.The rheological studies show that the mechanical stability of different oil-water ratio emulsions is different,and the system with oil-water ratio of 1:4 is the most stable case,we have not noticed any phase separation and fluidity in it even after placed at room temperature for four months,indicating the HIPE system has a high storage stability.And the effect of changes in the content of stabilizer,initiator(KPS),and crosslinking agent(DVB)on the pore structure of the PILs material was further investigated while maintaining the volume of the dispersed phase at 80%,the results show that the pore structure of the material can be finely adjusted according to the above conditions.Secondly,the contact angle tests of the porous PILs monoliths(contact angle greater than 150°)indicate that the Porous PILs materials have superhydrophobic properties.The second part of the work studies the performance of the hydrophobic Porous PILs materials,including carbon material preparation and dye adsorption separation.Firstly,we carbonized the Porous PILs precursor at different temperatures to obtain carbon materials with different degrees of graphitization.Although the geometrical shape of the monolith materials in the carbonization process shrinks obviously,it does not collapse and rupture.Furthermore,SEM tests show that the porous structure of the PILs material remains intact after the high temperature carbonization process.Moreover,the BET tests demonstrate that the carbon material has a rich microporous structure.Based on our study we conclude that the porous PILs material prepared in this work is a highly efficient precursor of porous carbon materials.XPS,TEM and XRD were employed to investigate the elemental composition of the porous carbon material and the way of carbon accumulation,the characterizations indicate that carbonized materials at 800 ? are more graphitized and have better crystallinity.Secondly,we studied the adsorption separation efficiency of anionic dyes(xylenol orange,methyl orange or orange II)in methanol by using hydrophobic porous PILs materials as adsorbents,showing that the removal efficiency of xylenol orange is as high as 92.8%.The high efficient adsorption of anionic dyescould be attributed to synergistic effects of electrostatic interaction between PIL and the anionic dye.Therefore,porous PILs material prepared in this work is able to remove the anionic impurity contamination in organic solvents effectively,and it is also expected to have excellent performance in selectively adsorbing anionic dyes in mixed dyes.