Alkynylated Modification Of Cellulose Nanocrystals And Study On Its Modified Materials

It is the new researching hotspot of composite materials that biomass nano-materials are used as fillers to modify polymeric matrix. In particular, by virtue of its abundance, high strength and stiffness, low weight and biodegradability, cellulose nanocrystals instead of inorganic nano-fillers are widely used in the preparation of nanocomposites. Due to the abundant polar hydroxyl groups on its surface, cellulose nannocrystals are more easily dispersed in polymeric matrix and have better interfacial interaction with the matrix, which play the enhancement effect of nanocrystals. In order to enrich the kinds of cellulose nanocrystals modified materials and to expand its range of applications, the surface modification of cellulose nanocrystals that improve solubility/dispersion in organic solvents and compatibility/interaction between nano-fillers and matrix change their intrinsic surface properties, which has become a consensus. However, because of its many advantages such as high efficiency, high yield and high selectivity, click chemistry are widely used in material synthesis and modification. To combine click chemistry and nanocomposite materials, offers a new way for the preparation of new highperformance nanocomposite materials.This work is use of reactive hydroxyl groups on the cellulose nanocrystals surface and independent synthetic alkynyl anhydride(4-oxo-4-(prop-2-yn-1-yloxy) butanoic anhydride) to occur esterification reaction to prepare alkynylated cellulose nanocrystals(ACNC). A series of reactive GAP(glycidyl azide polymer)/PTPB(propargyl-terminated polybutadiene) nanocomposites reinforced by alkynylated cellulose nanocrystals were synthesized from the Huisgen click chemistry. Then, swelling test, tensile test, thermodynamic test and morphology test were carried out to investigate the structure-properties relationship of the nanocomposite materials.The main researching results of this thesis are as follows: ? high-efficiency substitution(about 81.7%) of the hydroxyl groups by alkynyl groups on the surface of cellulose nanocrystals was realized through the esterification reaction between the alkynylated anhydride compound and cellulose nanocrystals. Meanwhile, the crystalline structure and morphology of ACNC have not been destroyed and the dispersity of them in organic solvent(tetrahydrofuran) has been remarkably improved. ? taking advantage of Huisgen reaction acted as the curing and compatibilizingintegrated method, ACNC was introduced in the reactive GAP/PTPB polymeric matrix for the preparation of nanocomposites. In comparison with the neat GAP/PTPB material, the tensile strength, Young's modulus, and elongation at break of the nanocomposite(containing only 1.0 wt% ACNC) were increased by 103.3%, 100.0% and 12.4%, respectively.Surface alkynylation of cellulose nanocrytals successfully improved the dispersion of cellulose nanocrystals in organic solvent and the interaction between the nanocrystals with polymeric matrix, without destroying its original morphology and crystal structure, and further alkynylated cellulose nanocrystals were introduced into the reactive polymeric matrix(GAP/PTPB), to prepare composites reinforced by the reactive biomass nano-fillers.