| Cellulose is an abundant renewable natural polysaccharides, and its development andutilization have great significance to alleviate resource constraints as well as energy crisis.The processing of cellulose is restricted by its limited solubility in common solvents and itsinability to melt because of its numerous intermolecular and intramolecular hydrogen bonding.In recent years, a great breakthrough has been made by the utilization of ionic liquids as thesolvents of natural polysaccharides. This has been providing a new and versatile platform forthe wide utilization of biomass resources and creation of novel functional materials. In lightof recent development of regarding applications of ionic liquids in natural polyxaccharides,the work of this thesis is mainly concentrated on the following issues:Two dialkylimidazolium-based ionic liquids,1-butyl-3-methylimidazolium(BMIMCl)and1-allyl-3-methylimidazolium chloride (AMIMCl), were synthesized by employingcontrolled microwave heating and the protocol is then compared with the similar preparationusing conventional heating (oil bath at80℃). The results showed an efficientmicrowave-assisted preparation of1,3-dialkylimidazolium halides has reduced the reactiontime by several times in a process that avoids the use of a large excess of alkyl halides/orgaicsolvents as the reaction medium. Upon microwave irradiation, the ionic liquid starts formingwhich increases the polarity of the reaction medium thereby increasing the rate of microwaveabsorption.The production yields and the utilization ratio of raw material were also increasedto some degree. FT-IR and13C NMRwere carried out and results shown the two ionic liquidswere successfully synthesized.Dissolution of absorbent cotton cellulose with high degree of polymerization in ionicliquid1-allyl-3-methylimidazolium chloride (AMIMCl) was studied. The experimentalprocess was observed by the polar optical microscope and the results showed that AMIMCl isan efficient solvent for absorbent cellulose. The relationship between reaction temperature、reaction time and the solubility was further studied; the effects of reaction time and reactiontemperature on the DS of cellulose and on the mass loss during the dissolving process wasalso studied. Results indicated that the dissolving process was accelerated by increasingreaction temperature, whereas more DP drop and mass loss happened as well; longer reactiontime also caused more degradation of cellulose. The proper condition for dissolving absorbentcotton cellulose in AMIMCl was created. The physic-chemical properties of the regeneratedcellulose films have been characterized by X-ray diffractometer (XRD), infraredspectrometric analyzer (FTIR), thermogravimetric analysis (TGA) instrument. There was no change on the chemical structure of cellulose after dissolution and regeneration in AMIMCl,but the crystal structure changed from I to II and the thermo stability decreased a little.By using acrylamide as monomer and ammonium persulfate (APS) as an catalyst, basedon the principle of free radical polymerization, cellulose/acrylamide graft copolymers(cellulose-graft-PAM) with a grafting ration of PAM to cellulose in a range of100%～300%were successfully synthesized in ionic liquid1-butyl-3-methylimidazolium chloride. Theweight ratios of AM monomer to cellulose, reaction temperature, reaction time as well ascatalyst amount affected the graft reaction, those influences were studied and the optimumreaction condition was created. The structure and thermal properties of cellulose-g-PAMcopolymers were characterized by FT-IR and thermogravimetric analysis (TGA). The TGAresults revealed that the thermo stability of the grafted polymer was between that of originalcellulose and that of regenerated cellulose. |
PDF Full Text Request