Surface Modification Of Nanocellulose Via Surface-initiated ATRP

Cellulose nanocrystals surface is modifation by synthetic polymers of differernt monomers through ATRP(Atom Transfer Radical Polymerization),getting different modification cellulose nanocrystals and research the various physical and chemical properties of the modified cellulose nanocrytals.The specific research work is as follow:Synthesis a ATRP initiators with specific structure and prepared three different synthetic polymers. First synthesized ATRP intiators with cycloenones structure,then styrene(St),benzene methylacrylate(MMA),benzyl ester acid tert-butanol(tBA) as three different monimers,CuBr as catalyst,anisole as solvent,PMEDTA as a ligand,recated under80℃ to synthesize corresponding polymers and research the molecular weigh distribution of synthetic polymers by gel permeation chromatography.Results show the three different monimers all can be polymerized and study the reaction kinetics find that the molecular weigh of ploymers increasing with reaction time in a linear relationship which can be useful in the next research.And the conversion of the monomers and the molecular weigh distribution also be studied,showed a narrow DPI<1.3.Preparation of nanocrystalline cellulose azide(NCC-N3),high crystallinity of nanocrystalline cellulose was prepared by sulfuric acid solution.The morphology of nanocrystalline cellulose is nanoscale rod-like structure which is observed by TEM.Pyridine(Py) as solvent, p-toluenesulfonyl chloride(PTSC) and sodium azide(Na N3) as reactants,react with nanocrystalline cellulose to get nanocrystalline cellulose azide(NCC-N3).And we analysis the groups N3 was successful introduced to the surface of nanocrystalline cellulose by FT-IR.The grafted ratio of the N3 group is 0.15 which was get by elemental nanlysis and the hydroxyl group on the surface of nanocrystalline cellulose all were replaced by N3 group through crystal structure analysis.Synthetic cellulose nanocrystals subtituted by polymers by click chemistry.First thepolystyrene with 30 to 40 units was dispersed in NN-dimethyl formamide(DMF),then the cycloenones was deprotected and turned to the tension alkyne structure under ultraviolet light of a wavelength of 254 nm.Then the synthetic polymer reacted with modified nanocrystals at the ratio 1.2:1 in room temperature to get NCC-PS.In the end we study the grafting efficiency through ultraviolet(UV), Fourier Transform Infrared Spectrometer(FT-IR), elemental analysis(EA), thermal gravimetric analysis(TGA), differential scanning calorimetry analysis(DSC),and the change of physical and chemical properties of grafted NCC.The results showed cellulose nanocrystals obtain the thermal decomposition temperature of the grafted polymers,this can also proved the successful grafting of the polymer.