Synthesis And Self-assembly Of Functional Hyperbranched Poly(ionic Liquids)

Ionic liquids（ILs）is a kind of organic salt at room temperature,which consists of cations and anions completely.Ionic liquids possess many advantages such as low saturated vapor pressure,excellent heat stability and chemical stability,strong electrical conductivity,good designability and so on.Poly（ionic liquids）（PILs）is the polymer of ionic liquids.Combining IL’s advantages with the excellent processibility of polymers,PILs could be applied in many areas such as electrolytes of electrochemical devices,dispersant,catalysts,sorption and separation gases,construction of porous polymers,smart materials and so on.Molecular self-assembly is a process to obtain molecular aggregates with ordered structures and special functionalities through weak intermolecular interactions,and is very important for the construction of nanomaterial.Thus,it is hopeful to derive a new academic growth point by integrating PILs with self-assembly.On the one hand,because of the abundance of ionizable groups in PILs,especially hyperbranched poly（ionic liquids）（HBPILs）,and dramatic asymmetry in charge,mass,and size between the HBPILs backbones and the counter-ions,co-ions,and solvent molecules,PILs have a rich and significantly different phase behavior and tend to achieve unconventional assemblies compared to conventional neutral macromolecules.On the other hand,self-assembly of PILs could endow self-assemblies with excellent properties of ionic liquids,for example the modification or functionalization of self-assemblies can be realized by simple ionic exchanging.However,the research of poly（ionic liquids）self-assembly is in the bud nowadays.To our knowledge,there are few reports on the self-assembly of HBPILs.Based on the research situation on the synthesis,property,self-assembly and application of ILs,PILs and branched PILs,we prepared two kinds of novel HBPIL molecules,and investigated their self-assembly behaviors in aqueous solution and their possible applications.The main contents and conclusions are summarized as follows:1.Preparation of SO₃^2--detecting polymer vesicles through the self-assembly of hyperbranched polymeric ionic liquids:HBPILs[HSP-MIM][OTs]with tosylate（OTs）as anionic part and1-methylimidazoles（MIM）as cation part was prepared successfully by the reaction of 1-methylimidazoles and OTs grafted amphiphilic hyper-branched multiarm copolymer.Then,by a simple anion-exchange,we combined the functional small-molecule probe of acid fuchsin（AF）with HBPILs sucessfully.The obtained amphiphilic[HSP-MIM][AF]could self-assemble into vesicles in water with the functional ion pairs enriching on the surface.Upon the addition of sulfite,the structure of conjugated AF was interrupted due to the nucleophilic attack of SO₃^2-,and the maximum absorption peak at 544 nm disappeared accompanying with the color change of solution from magenta to colorless.So the obtained HBPIL vesicle can be used as novel SO₂ derivatives sensor with high sensitivity and visualization.Due to the functional ion pairs enriching on the surface,the SO₃^2-detection limit of HBPILs vesicle is as low as 0.138μM,which is about 1.5 orders of magnitude lower than that of AFs.2.Preparation of CO₂ responsive polymer vesicles through the self-assembly of hyperbranched polymeric ionic liquids:The amphiphilic HBPIL of[HPEI-P][Br]with bromine ion（Br^-）as anionic part and trihexylphosphine（P）as cation part was prepared through the graft of trihexylphosphine groups onto the terminal of hyperbranched polyethylene imine（HPEI）.By adjusting the ratio of reactants and reaction conditions,we obtained a series of[HPEI-P][Br]with the different trihexylphosphine graft ratio.[HPEI-P][Br]could self-assemble into vesicles in water with a diameter of around 200 nm.Moreover,the effects of the self-assembly methods,solvent,graft ratio of[HPEI-P][Br]on the self-assemblies morpology were investigated.The assembly processes were careful characterized by NMR technique and the corresponding mechanisms were also discussed.The study found that[HPEI-P][Br]vesicle showed unique responsiveness to the CO₂,similar to the deformation mode of“Fugu”.