Preparation And Characterization Of Bio-based Polymers Derived From Lignocellulose

Biomass is one of the most abundant renewable resources. The development of bio-based polymers to replace fossil-based polymers is one of the most effective strategies to relieve the current oil crisis. This thesis focuses on preparation of bio-based monomers and polymers derived from lignocellulose and its platform molecules. The structure and thermal properties of bio-based polymers were investigated.Novel bio-based aliphatic-aromatic monomers were synthesized through condensation between cellulose-based platform molecules, including levulinic acid and methyl levulinate, and lignin-based platform molecules, including vanillin aldehyde, syringaldehyde and p-hydroxybenzaldehyde. Bio-based polyesters were obtained by self melt polycondensantion of the above monomers. Effects of different catalysts and reaction conditions on the condensation and polymerization were studied. The results demonstrated that pyrrolidine-acetic acid was the most effective catalyst. The nuclear magnetic resonance (NMR), Fourier transform infrared spectrometry (FTIR), X-ray diffraction (XRD), gel permeation chromatography (GPC), thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC) revealed that the structures of bio-based polyester were similar to that of PET and their glass transition temperature were higher than that of PET.Lignin-based bisphenol was prepared through condensation between creosol derived from lignin and formaldehyde in water using lignosulfonic acid (LSA) as catalyst and used to prepared lignin-based polycarbonate. The effect of different catalyst and the recycling test of LSA were investigated. A plausible reaction mechanism was proposed. The results showed that the catalytic effect of LSA was higher than mineral acids. It was convenient to recover LSA which could be reused. The structure, molecular weight and thermal properties of obtained lignin-based polycarbonate were analyzed by NMR, FTIR, XRD, viscosity method, TGA and DSC. The molecular weight, glass transfer temperature and melt temperature of lignin-based polycarbonate was 46000 g/mol,122? and 314?, respectively.The lignin-based bisphenol was converted to bis(cyclic carbonate) (BCC) monomer via the glycidylation and cycloaddition. The lignin-based polyurethanes were obtained via ring-opening polymerization between BCC and 1,6-hexamethylene diamine, isophorondiamine and diaminehydrate in DMSO. The conversion and yields of ring-opening polymerization can be enhanced by either increasing reaction temperature or adding catalyst. The structure, molecular weight and thermal properties of the lignin-based polyurethanes were analyzed by NMR, FTIR, XRD, GPC, TGA and DSC. The results revealed that 1,6-hexamethylene diamine was the most effect with conversion of 100% and the molecular weight of obtained polyurethane was 47000 g/mol.Cellulosic poly(ionic liquid)s were obtained via chlorination-quaternization strategy, which required no catalyst and produced no by-products, and employed as catalysts in the cycloaddition between CO2 and epoxides. The degree of substitute reached 0.64 by optimizing the reaction conditions. NMR, FTIR, XRD, TGA and DSC demonstrated that cellulosic poly(ionic liquid) was amorphous and its thermal stability was lower than that of cellulose. The yield of cycloaddition reached 95% and the catalyst could be reused.