Anionic Functionalized1-allyl-3-Methyumizodalium Ionic Liquids As Excellent Solvent For Cellulose

As a kind of novel green solvent, Ionic liquids （ILs） have been successfully employed to processcellulose. However, the existing ionic liquids which can dissolve cellulose have many drawbacks such ashigh melting point, high viscosity, low thermal stability and among others. Therefore, it’s an inevitabletrend to develop new ionic liquids to efficiently dissolve cellulose under mild conditions. With the rapiddevelopment of ionic liquids, the structure controllability of ionic liquids has been more and moreunderstood and applied in practical process, and it is possible to design and develop new ionic liquid withdesired performance for dissolution of cellulose. As a part of of the project supported by the National HighTechnology Research and Development Program （863Program, No.2007AA05Z454）, a series of anionicfunctionalized1-allyl-3-methylimizodalium ionic liquids have been synthesized in present work. Theeffects of structure of ionic liquids and the additon of polar aprotic solvent to IL on their physicochemicalproperties and cellulose solubility were studied systematically. The main contents are as follows:1. Eight new ionic liquids, composed by1-allyl-3-methylimizodalium cation （[Amim]+） and theBronsted basic anions [HCOO]-,[CH₃COO]^-,[CH₃CH₂COO]^-,[CH₃CH₂CH₂COO]^-,[C₆H₅COO]^-,[HOCH₂COO]^-,[CH₃CHOHCOO]-and [N（CN）₂]^-were synthesized and characterized. Theirphysicochemical properties such as glass transition temperature, thermal stability, density, viscosity andconductivity were measured, and the effects of anionic structure on these properties were studied in details.Also, Arrhenius plot and Walden rule were used to evaluate the fragility and the ion-ion interaction of allthe ILs.2. Solubilities of microcrystalline cellulose in the ILs at different temperature were determined. Theeffect of the anionic structure on the solubilities of cellulose in the ILs was investigated by means ofsolvatochromic UV/vis probe and¹H NMR chemical shift technique. The possible mechanism of cellulosedissolution was clarified by¹³C NMR chemical shift technique. The effects of regeneration process onthermal stability and molecular structure of cellulose was studied by thermogravimetric analysis, thedegrees of polymerization determination and X-ray diffraction analysis.3.[Amim][CH₃COO] was used as a model IL to study the effect of the additon of polar aprotic solvents like dimethyl sulfoxide （DMSO）, N,N-dimethylformamide （DMF）, N,N-dimethyl-acetamide（DMAc）, and N-methylimidazole （MIM） on the solubility of cellulose. The possible role of the co-solventin the dissolution of cellulose was investigated by means of¹H NMR and conductimetric methods. At thesame time, DMSO was used to understand the effect of anionic structure of the ILs on the cellulosesolubility in IL/DMSO solvent.