Preparation And Properties Of Pullulan Modified By Carboxyl Functionalized Ionic Liquids

Pullulan is a natural,non-toxic and degradable biopolymer.It has good film-forming properties.It has no electrical conductivity,which limits its application as a polymer electrolyte greatly.Ionic liquids are called"green solvents".It is environmentally friendly and conductive,and has a certain antibacterial ability.Therefore,the modification of pullulan with ionic liquid can improve the conductivity of pullulan,and expand the application of pullulan and its derivatives.In this paper,two composite films of pullulan were prepared and a pullulan derivative which is insoluble in water was prepared.First,the carboxyl functionalized imidazolium ionic liquid[CEBIM][PF₆]was synthesized through quaternary ammonium salt formation reaction and ion exchange reaction.The successful synthesis of the product was proved by FT-IR and ¹H NMR.Then pullulan was physically blended with the synthetic carboxyl functionalized ionic liquid,and the solutions were cast into films.Further testing found that with the increase of[CEBIM][PF₆]ionic liquid addition,the dielectric constant、dielectric loss and electrical conductivity of the composite films are gradually increasing,and the direct current conductivity has increased by four orders of magnitude,so[CEBIM][PF₆]ionic liquid can be used as an antistatic agent to enhance the antistatic ability of pullulan film.Second,the carboxyl functional imidazolium ionic liquid with polymerizable double bonds[CEVIM][PF₆]was synthesized by quaternization reaction and ion exchange reaction,and through free radical polymerization,the polyionic liquid P[CEVIM][PF₆]was obtained.The successful synthesis of the product was proved by FT-IR and ¹H NMR.Then pullulan was physically blended with the synthesized polyionic liquid,and the solutions were cast into films,through testing,it is found that P[CEVIM][PF₆]/Pullulan composite film has good visible light transmittance.With the increase of polyionic liquid P[CEVIM][PF₆],the conductivity of the film gradually increases,which enhances the antistatic ability of pullulan film.Third,the ionic liquid[CEBIM][PF₆]was grafted onto pullulan through esterification reaction,and the successful synthesis of the product was verified by FT-IR and ¹H NMR.The testing found that the conductivity of pullulan derivatives grafted with[CEBIM][PF₆]ionic liquid is slightly enhanced;at the same time,it was found that with the increase of grafting rate,the solubility of pullulan will be changed,and water-insoluble pullulan derivatives will be obtained.