Study Of Transesterification And Ring-opening Grafting Polymerization Of Cellulose In CO₂/DBU/DMSO

Polymeric materials find important applications in many filed such as plastics, fiber, coating, etc. However, the traditional polymers mainly depend on fossil resources (coal, oil, and nature gas). The development and application of new materials has attracted considerable attention due to the shortage of petrochemical resources. The scarcity of the petrochemical will inevitably lead to energy shortages and high cost, restricting the sustainable development of society. Over-exploited oil and other fossil resources could create environmental problems. As regards the oil resources, it is vital to find suitable biomaterials.In this paper, we used cotton pulp and microcrystalline cellulose to synthesize a variety of cellulose esters, andthe structures and properties of cellulose ester derivatives were characterized. The results indicated that it is an efficient and green approach to synthesize new cellulose esters.The cellulose benzoate was synthesized through transesterification of cotton pulp and methyl benzenecarboxylate in DMSO. In this reaction, 1,8-Diazabicyclo[5.4.0]undec-7-ene (DBU) was used as an organic base and cotton pulp was activated at 50 ℃ under 0.2 MPa CO2. The effects of the mole ratio of methyl benzenecarboxylate and cotton pulp, the reaction time and temperature on the degree of substitution (DS) of cellulose were studied. The structure of the cellulose benzoate was analyzed by NMR, FTIR, XRD, TGA, and DSC. The optimum reaction activity was obtained at 120 ℃ when the mole ratio of methyl benzenecarboxylate to cotton pulp was 5.0, the DS of cellulose was as high as 0.28. Regardless of the reaction conditions, the DS of cellulose benzoate was almost unchanged. The TGA and DSC analyses indicated that the thermal stability of cellulose benzoate was decreased and the glass transition temperature was 57 ℃. The XRD analysis indicated that the cellulose crystalline state transformation from cellulose Ⅰ to cellulose Ⅱ during the reaction. The cellulose-graft-poly(σ-valerolactone) was synthesized through ring-opening polymerization of cellulose and σ-valerolactone in DMSO. In this reaction, 1,8-Diazabicyclo[5.4.0]undec-7-ene (DBU) was used as an organic base and cellulose was activated at 50℃ under 0.2 MPa CO2. The effects of the mole ratio of σ-valerolactone and cellulose, the reaction time and temperature on the degree of substitution (DS) of cellulose were studied. The structure of the cellulose-graft-poly(σ-valerolactone) was characterized by NMR, FTIR, XRD, TGA, DSC and GPC to explore the relationship between structure and properties. The XRD analysis indicated that the cellulose crystalline state transformation from cellulose I to cellulose II during the reaction, cellulose-graft-poly(a-valerolactone) formed a new crystal structure.We have synthesized some bio-based platform chemicals (5-hydroxymethy1 furfural and vanillin) derivatives through acylation and aldol reactions. Then, these monomers characterized by NMR, FTIR and high resolution mass spectrum. The synthesis of polyesters through Tishchenko Reaction (RuH2(PPh3)4 or SmI2 as catalyst) and aldol reaction (Pyrrolidine and AcOH as catalyst) was achieved.