Design,Synthesis And Property Of Bio-Based Polycarbonate

With the depletion of fossil resources and the intensification of global greenhouse gas effects,the comprehensive utilization of biomass resources and carbon dioxide（CO₂）has become a hot spot in the world in recent years.Bio-based materials are gradually becoming a new leading industry that leads the scientific and technological innovation and economic development of the contemporary world due to its characteristics of green,environmental friendliness and resource conservation.Cellulose is the most naturally occurring biopolymer and has the characteristics of biodegradability,easy modification,and good biocompatibility.This dissertation focuses on the research of the CO₂ derivatization and dissolution technology of cellulose in the presence of organic bases.The synthesis and properties of novel cellulose carbonate thermoplastic materials around the capture of "CO₂" are studied.The specific research contents are as follows:（1）Based on the dissolution and derivation of cellulose in the novel 1,8-diazabicyclo[5.4.0]undec-7-ene（DBU）/CO₂ system followed by the addition of dimethyl carbonate via the insitu organocatalysis by DBU.When the molar ratio of AGU:DBU=3:3 and the co-solvent is DMSO,cellulose can be complete dissolution in DBU/DMSO/CO₂ system.In this system,cellulose methyl carbonate with a DS of 1.09 and Tg of 63.0 °C was achieved after 12 h at 60 °C with a molar ratio of dimethyl carbonate/AGU at 8:1.（2）A reversible cellulose carbonate polyionic liquid can be obtained through dissolving and activating cellulose based on the DBU/DMSO/CO₂ system and reacting with a halogenated compound to prepare cellulose carbonates.Using benzyl bromide as a model raw material,it was found that the optimal reaction conditions were 30 oC,4.0 MPa,12 h,OH:Br molar ratio was 1:1,cellulose benzyl carbonate with a DS of 1.73 was prepared.A solvent-evaporation method was used to prepare cellulose carbonate films with nano deep pits on the surface.The light transmittance of the films was 85 to 92% with the tensile strength was 26 to 49 MPa and the strain is 6.09-27.76%,what more attention that it exhibit a relative good ability in the CO₂ permeability is 2.13-50.2 Barrer.（3）Cellulose mixed carbonates were synthesized with mixed alkyl halides in DBU/DMSO/CO₂ system.As a result,different DS of cellulose mixed carbonate can be controllable prepared by controlling the proportion of mixed halogenated alkanes.When the proportion of the mixed bromide is the same,by adjusting the structure of the bromide,it is possible to controllable prepare the cellulose ethyl mixed carbonate with DS of 0.50⁰.60.And cellulose mixed carbonate films has good optical,mechanical,and gas separation performance.In this result,the light transmittance of carbonate films were between 85% and 92%,and the tensile length was 26⁴9MPa.The strain is 6.09-27.76%,and the CO₂ permeability is 2.13-50.2 Barrer.（4）A functional cellulose propylene carbonate with a DS of 1.51 and a Tg of 164.1 oC and functional cellulose propyne carbonate with a DS of 1.06 and a Tg of 105.2 oC were successfully prepared based on the DBU/DMSO/CO₂ system at 30 oC,4.0 MPa,12 h,OH:Br molar ratio of 1:1.In addition,cellulose propene/benzyl-thiol bi-functional carbonates and cellulose propyne/benzyl-thiol bi-functional carbonates were successfully prepared by thermally initiated and photo-initiated thiol-ene click chemistry,thiol-yne click chemistry,and cellulose propyne/triazole bifunctional carbonate were prepared by the Cu AAC-catalyzed azide-alkyne click chemistry.New derivatization strategies are provided for the preparation of chemicals and materials,as well as new technologies,new methods and theoretical support for the comprehensive utilization of biomass resources and CO₂ toward the homogeneous modification of DBU/DMSO/CO₂ system to prepare cellulose derivatives.