The Controllable Synthesis,Properties And Applications Of Cellulose Derivatives Pending Ketone Groups

Since the 20th century,petroleum-based polymer materials have played an irreplaceable role in the development of human civilization.However,with the social and economic development,the resource crisis and environmental problems caused by the large-scale and widespread application of petroleum-based polymers have become more and more serious.It is generally believed that it is imperative to realize the sustainable development of polymer industry,and it is well accepted that the use of bionewable resources as raw materials to prepare polymer materials will significant reduce the dependence on petroleum resources,thus resulting to a sustainable development of polymer industry.Cellulose is the most abundant natural polymers on the planet.However,cellulose is hard to be dissolved and can not be melt like common polymers due to their inherent hydrogen bonding network structure.Therefore,the facile dissolution and mild and desirable derivatization of cellulose is prime topic in order to increase their processablity and functionality.This thesis focuses on the controllable and green synthesis of cellulose esters pending ketone group,and identify their potential for further material synthesis via post-modification,and the main content was summarized as following:1.With the successful dissolution of cellulose in the newly developed solvent system CO₂/DBU/DMSO,the transesterification reaction between cellulose and commercial bio-based chemicals,such asα-angelica lactone,methyl levulinate or acetyl ethyl propionate was systematically studid by take the in situ catalytic performance of DBU in the solvent system,and a serial of cellulose levlinate ester with tunable degree of substitution was achieved.The effect of reaction conditions（reaction time,temperature and feed ratio）on the structure and properties of cellulose levulinate was systematically studied.The research results show that when the degree of substitution is greater than 0.59,the synthesized cellulose levulinate has good water solubility,and the cellulose levulinate film prepared with water as a solvent has a good water solubility with tensile strength of 72 Mpa,and the elongation at break reached26.7%with no plasticizer.In this paper,the mechanism of enol isomerism based on keto-carbonyl group was proposed to promote the reconfiguration of cellulose hydrogen bond network,and to improve the mechanical properties of the material and internal plasticization.2.It is the first time for controlled synthesis of cellulose levulinate mixed ester using acid anhydride as acylating reagent using cellulose levulinate as a cellulose derivative platform.By controlling the carbon chain length of the anhydride,the glass transition temperature of the mixed ester was regulated.For example,the glass transition temperature of cellulose levulinate butyrate is 86.8 ^oC,and the glass transition temperature of cellulose levulinate propionate is 109.3 ^oC.The design and synthesis of new cellulose-based thermoplastic materials and application provides important theoretical and technical support.3.Based on the keto-carbonyl structure characteristics using cellulose levulinate as cellulose derivative platform,the direct carbon chain extension and the dehydration and condensation of cellulose levulinate is realized,and long chain and large steric hindrance are developed through Aldol condensation reaction.The synthesis strategy of cellulose carboxylate,anti-free radical and photoactive cellulose carboxylate were developed.The structure and properties of the materials were researched through FT-IR,¹H-NMR,¹³C-NMR,DSC,TGA,the relationship between the material structure and thermal properties was clarified.4.Cellulose acetoacetate was successful prepared through the reaction of cellulose and diketene in Amim Cl ionic liquids without adding external catalyst.The effect of reaction time,temperature and feed ratio on the substitution degress of cellulose acetoacetate was systematically investigated.The Biginelli reaction of cellulose acetoacetate was studied by using lignin-based phenolic aldehyde as the reactant,and series of anti-free radical and fluorescent cellulosic dihydropyrimidin-2（H）-ones)were successfully prepared.The structure and properties of the as-prepared materials were confirmed and evaluated by using FT-IR,¹H-NMR,¹³C-NMR,DSC,TGA,fluorescence spectroscopy and other characterization methods.