Preparation And Application Of Nanocellulose Investigated By Synchrotron Radiation X-ray Scattering Technique

Cellulose is the most copious natural biopolymer metarial on earth,which is attracting considerable interest as an attractive biorenewable feed stock due to its biodegradability,nontoxicity,structural rigidity,robustness and biocompatibility.Cellulose nanofibrils(CNF)not only retains the desirable physical properties of natural cellulose,but also exhibits promising nanomaterial properties.In order to quantitatively control the crystal type and crystallinity of CNF,it will have a broader application prospect in more material fields in the future.As a Pickering emulsifier,investigating the influence of CNF size and concentration on emulsion stability will be explored to broaden its potential application in various industries.The main works done by the author are listed below:1.A two-step alkali/oxidation process has been presented to efficiently convert waste sugarcane bagasse(SCB)into cellulose nanofibrils(CNF)whose structures have been characterized using a range of analytical techniques(SR-WAXS,IR,TEM and DLS).Increasing the concentration of the Na OH solution from 10 to 16 wt% in the first step results in a gradual increase in cellulose II content from 0 to >99%,which also produces a corresponding increase in fiber crystallinity index from 32 to61%.Varying the concentration of Na Cl O used in the second oxidative step enables the morphologies of the CNF to be reliably controlled,with fiber lengths decreasing from micrometer to nanometer levels as the amount of Na Cl O oxidant used is increased.This simple two-step alkaline/oxidative treatment process enables SCB to be converted into CNF exhibiting different polymorphic and morphological properties,thus enabling their economic and reproducible production as nanostructured materials for numerous applications.2.The two-step alkali/ TEMPO-mediated oxidation process also can be used to efficiently convert jute fibers into CNF with the same crystalline polymorph and different aspect ratios and concentrations.These CNF are used to prepare oil-in-water Pickering emulsions as promising stabilizer,and the effects of aspect ratio ratio and concentration of CNF on emulsifying capacity and emulsion stability are investigated.Under the same dosage,CNF with larger aspect ratio will connect part of the surface of many droplets,forming loose multilayer structure;CNF with smaller aspect ratio is more likely to cover the entire droplet,and due to the mutual repulsion of electrostatic repulsion brought by carboxyl groups contained in CNF,the aggregation between droplets is prevented,and the emulsion droplets are connected into a spatial network structure,thus forming a more stable O/W two-phase structure.In the range of ensuring the fluidity of emulsion,higher concentration of CNF will make the spatial network structure between droplets more stable,and achieve better emulsifying ability and stability.Our results improve understanding about the mechanism by which CNF emulsifier morphology affects emulsifying capacity and stability,and promote the expansion of its potential applications.3.In order to investigate the multistage structural evolution of emulsion and other fluid samples under temperature and pressure changes,an experimental method of synchrotron radiation X-ray scattering and Raman spectroscopy was developed at the BL16B1 Small Angle X-ray Scattering beamline of SSRF,as well as a set of matched temperature and pressure controlled sample chamber.