Study On Dissolution Of Cellulose In New Solvent System And Its Mechanism

Cellulose, as the most abundant biorenewable organic polymer on the earth, hasmany good characteristics such as biodegradable and low toxicity. In recent years,non-renewable energy resources are facing economic challenges such as decreasingreserves, increasing prices and so on, which make cellulose attracting much interest ofresearchers. Cellulose is insoluble in most conventional solvents for its numerous inter-and intra-molecular hydrogen bonds, which limits the development of cellulose. Thus, thediscovery of novel solvents with advantageous properties has always been of interest tothe field.Four cellulose solvent systems are synthesized and dissolution of cellulose in thesesolvents are studied. The polarized optical microscope is used for observing directdissolution of cellulose. The both original cellulose and regenerated cellulose arecharacterized by Fourier Transform Infrared Spectroscopy (FT-IR), X-ray Diffraction(XRD), Thermogravimetry (TG) measurements and Scanning Electron Microscopy (SEM).The results show ionic liquids are promising solvent for cellulose with designable andeasy recovery. The major results obtained in the study include as following:Three kinds of NaOH/amides/aqueous solution are synthesized, of which the bestcellulose solvent is NaOH/urea/caprolactam/aqueous solvent. The best ratio ofNaOH/urea/caprolactam/aqueous in solution is (wt): urea10%, caprolactam4%, NaOH8%. The optimal solution temperature is-10℃and the solubility reaches5.24%underthese conditions.A series of imidazolium ionic liquids with different cations and anions is synthesizedand characterized by Mass Spectrometry (MS)、 FT-IR and1H Nuclear MagneticResonance (NMR). The process of cellulose dissolution and regeneration in ionic liquidshas been discussed. The results show phosphate-based ionic liquids are potential solventfor cellulose because of simple synthetic process, high atom economical selectivity andbetter solubility of cellulose.Dissolution temperature has an influence on performance of regeneration cellulose. Itshows that with the dissolution temperature increased, the dissolution time and DP ofregenerated cellulose are reduced. It is better to dissolve cellulose below100℃. Resultsshow that the four systems are all non-derivatizing cellulose solution. The crystal ofregenerated cellulose is converted to cellulose II from cellulose I and the thermostabilityof regenerated cellulose decreased. Regenerated cellulose films are homogeneous and dense. The cellulose regenerated from [EMIM][DEP] is with excellent performance andits properties are closer to the original cellulose.