Non-derivative Dissolving Of Cellulose And Preparations Of Novel Cellulose Based Hydrogel

Functional studies of bio-based materials is one of important research fields in science and industry,and most researches focus on the functionalization and intellectualization of bio-based materials with the rapid development of material science and biological medicine on the basis of traditional application of this kind of material,and dedicated to develop in the direction of the fine and intelligent.Among the many reasons behind the continuous search for new applications of bio-based polymers are the polymer‘s biocompatibility,biodegradability,non-toxicity,good modification and natural abundance.As the typical bio-polymer,the functional research of cellulose is one of the most attractive fields,and the discovery of all kinds novel non-aqueous solvents created good opportunity for the developing of biological materials with new functions and special properties.Based on special properties of natural biological materials,to develop the functional research,broaden even break their original traditional application fields is of great significance.This paper studies the nonderivative dissolving mechanism of cellulose and developed the related thermodynamics model,researched and developed a serial new type of functional cellulose hydrogel materials on the base of ionic liquids as solvent,and made a systematic study on the formation mechanism,preparation of novel cellulose hydrogels and aerogels,material properties,functionalized modifications,applications,etc.This paper is consisted of seven chapters:Chapter 1: Introduction.The general characteristics of cellulose,hydrogel,ionic liquids were briefly introduced,and the research status and new development of non-derivate dissolving of cellulose,gel materiel and the applications of Ionic Liquids in cellulose fields in the domestic and overseas were synthetically narrated.Summarized the common characteristics of hydrogel on this basis,the preparation feasibility of novel cellulose bio-hydrogel adopt Ionic Liquids as solvent,and the research objectives and contents of this thesis were proposed.Chapter 2: The evolution behavior and dissolution mechanism of cellulose in aqueous solvent were discussed in this section.The dissolution evolution behavior of cellulose with different structure and morphology in N-methylmorpholine-N-oxide(NMMO)/H2 O solution,a typical aqueous solvent,were investigated.The model for dissolving evolution of polymer with the structure of amorphous co-existing with crystalline regions and the solvent penetrating model for the swelling dissolution of cellulose fibre were developed.Chapter 3: Unraveling the mechanism of non-derivative dissolution of cellulose and polysaccharide through thermodynamic analyses on the basic of ionic liquids as solvent.The thermodynamic mechanism for non-derivative dissolution of cellulose is unraveled on the basic of cellulose and other similar struture biopolymers adopt a serial non-aqueous solvent,Ionic liquids,as solvent,and combined with the Density Functional Theory(DFT)to quantitatively characterize the thermodynamic transformation in the dissolving process.The thermodynamic dissolving formulas of cellulose and other similar biopolymers involved entropy,enthalpy,and temperature influence factors which caused the dissolving capacity of non-derivative solvent changing were derived based on the thermodynamic discussion;the study also involved some other influence factors on the dissolving property of the cellulose non-derivative dissolution.Chapter 4: Preparations and formation mechanism of novel cellulose hydrogel membrane based on ionic liquid were discussed in this section.The cellulose hydorgel membranes with homogenous macrostructures,excellent mechanical properties,porous interior structure and good transmittance were prepared using functionalized ionic liquid 1-butyl-3-methylimidazolium chloride([Bmin]+Cl-)as solvent.The influences of pre-gelation temperature,pre-gelation time and coagulation batch temperature on the properties and morphological features of the prepared hydorgel membrances were discussed.In addition,the possible formation mechanism of cellulose hydrogel was primary discussed and the model of the hydrogel formation is established.Analyzed the functions of hydrogen bonds between intra-and inter-molecular cellulose molecules and the formation of well-organized aggregate sheets which formed by the hydrophobic sides sticking due to cellulose amphiphilicity to the structure and propertied of the cellulose hydrogel.Chapter 5: The self-assembly of novel cellulose gel with the chiral nematic structure and the formation mechanism of cellulose gel were discussed.The novel chiral nematic hydrogel and iridescent cellulose aerogel with the chiral nematic structure were prepared for the first time by the self-assembly of cellulose molecules adjusting self-structure in the immersion-precipitation phase transferring process based on the ionic liquid,1-allyl-3-methylimidazolium chloride([Amim]+Cl-)as solvent.The formation process and formation state of cellulose gel were tract studied by synchrotron X-ray diffraction small sacttering and wide angle X-ray diffraction measurements(SAXS and WAXD),and the formation mechanism of cellulose hydrogel and the formation process and mechanism of chiral nematic gel were investigated,further more developed the mechanism formation model of cellulose chiral nematic gel.Chapter 6: Preparations,properties and the composite mechanism of cellulose/polyvinyl alcohol(PVA)bio-composite hydrogel membranes.The novel cellulose/PVA composite gels and membranes were prepared and characterized,taking ionic liquid [Bmim]+Ac-as solvent.The cellulose and PVA show relatively good miscibility in selected ionic liquid,the formed hydrogen bonds due to the presence of large amounts of hydroxyl groups in the molecular chains of cellulose and PVA molecular chains act as the physical crossing junctions formed the cellulose/PVA composite hydrogel.The crossing junctions caused by the interactions of hydrogen bonds and the formed of aggregate sheets by the hydrophobic action of cellulose both enhanced the mechanical property and thermostability of the composite hydrogels,this is also the possible formation of cellulose/PVA composite hydrogels.Chapter 7: The preparations of novel cellulose/ phenylboronic acid composite intelligent bio-hydrogel and the glucose,p H-responsive behaviors were discussed in this section.Novel intelligent cellulose/4-vinyl-phenylboronic acid(VPBA)composite bio-hydrogels with glucose and p H-responsive were successfully prepared via electron beam irradiation technology at room temperature.The formation of cellulose/VPBA composite hydrogel can be attributed to strong interactions via hydrogen bonds between the cellulose molecules and the cross-linking between cellulose and VPBA,and the formation of interpenetrating polymer networks between the cellulose molecular chains and the poly-VPBA molecular chains.The p H and solvent responsiveness,etc characters of prepared cellulose/VPBA composite hysrogels were invested,self-regulation of insulin release behaviosrs from the hydogel in a serial glucose solution with different concentration were detected through Fluorescein isothyocyanate(FITC)-labeled insulin.