Nmr Spectroscopy Studies On The Interactions Between Imidazolium-based ILs And Solvents

Room temperature ionic liquids (RTILs), as a type of novel and environmentally benign media, havebecome the focus of research both in academic and industry nowadays. An upsurge of green chemistrybrings even more chances for the progressing of ILs research. Especially, the wide applications of celluloseon industry have brought tremendous development to the dissolution of cellulose in ILs. Many ILs andmixtures of ILs with some organic solvents have shown good effect on the dissolution of cellulose.However, there are very few researches on the interactions between ionic liquids and protic solvents andaprotic solvents. Thus further progress and application of ILs on the dissolution and regeneration ofcellulose has been restricted. In the present manuscript, a systematic research on the stucture ofimidazolium-based ionic liquids and the interactions between these ILs and protic and aprotic solvents hasbeen carried out by NMR Spectroscopy, and a possible steric configuration has been proposed, and themechanism about how ILs interact with solvents has been discussed, the effects of alkyl chain on theinteractions between ionic liquid and DMSO have been investigated. The results have provided theoreticalinformation for the applications of ILs in the dissolution and regeneration of cellulose.As a part of the project supported by the National Natural Science Foundation of China (No.21003039), the maincontents of the thesis are summarized as followed:(1) According to the synthetic methods reported in previous literature, imidazolium-based ionic liquids[C_nmim][CH₃COO](n=4,6,8),[C₄mim]Cl,[Amim]Cl(A=-CH₂CH=CH₂) have been synthesized andpurified.(2)¹H NMR,¹³C NMR, Spin-Lattice Relaxation Times (T₁) and¹H-¹H NOESY, for neat ionic liquids[C₄mim][CH₃COO] and [Amim]Cl(A=-CH₂CH=CH₂) at298.15K, and [C₄mim]Cl at333.15K, have beenperformed on a Bruker AV-400M NMR spectrometer. The interactions between the imidazolium cationsand the interactions between the imidazolium cations and anions have been discussed, and a potential stericconfiguration has been put forward, and the effects of the structures and the types of interactions in ILs onthe dissolution of cellulose have been discussed.(3)¹H NMR,¹³C NMR, Spin-Lattice Relaxation Times (T₁) and¹H-¹H NOESY for the mixed systems of [C₄mim][CH₃COO]/DMSO,[C₄mim][CH₃COO]/DMF,[C₄mim][CH₃COO]/DMAc and[C₄mim][CH₃COO]/H₂O,[C₄mim][CH₃COO]/MeOH have been carried out with a Bruker AV-400M NMRspectrometer at298.15K. The differences of the interaction between the ionic liquid [C₄mim][CH₃COO]and protic and aprotic solvents have been tested, and an explanation for the cellulose dissolution inILs/aprotic mixtures and regeneration in ILs/protic mixtures has been provided. Besides, a direction for thedissolution of cellulose at ambient temperature has been pointed out.(4)¹H NMR,¹³C NMR, Spin-Lattice Relaxation Times (T₁) and¹H-¹H NOESY for the mixed systemsof [Cnmim][CH₃COO](n=6,8)/DMSO have been measured using a Bruker AV-400M NMR spectrometer.The effects of the length of the substituited chains in the imidazolium cations on the interaction betweenILs and DMSO have been investigated.