Behavior Of Lyotropic Chiral Nematic Liquid Crystals Of Cellulose And Preparation Of Its Composites

Tunicate cellulose is the only one synthesized by animals,which has highly crystallinity and almost all monoclinic structure(I?).It is abundant renewable biological resource and offers great opportunities in food packaging,biodegradable materials and other fields.So the study of tunicate cellulose has important significance for the development and utilization of abundant marine renewable resources.At present,the research on tunicate cellulose mainly focuses on the method of acid hydrolysis,and 2,2,6,6-tetramethylpiperidine-1-oxyl radical(TEMPO)-NaBr-NaClO catalyzed oxidation system can oxidize primary hydroxyl groups on the cellulose surface to carboxyl groups under mild reaction conditions.It is a useful modification method to prepare cellulose nanocrystals(CNCs).In this thesis,cellulose was abstracted from the tunicate mantles,and TEMPO-oxidized tunicate cellulose nanocrystals(t-TOCNs)were prepared by hydrochloric acid hydrolysis and TEMPO-mediated oxidation system,respectively.The t-TOCNs was characterized by using Fourier transform infrared spectrometer(FT-IR),X-ray diffraction(XRD),polarizing optical microscope(POM),atomic force microscope(AFM)and Malvern particle size analyzer.The results indicate that the t-TOCNs consists mostly I? phase.The AFM observations confirmed that it had a wide distribution of sizes,its width is 20-40 nm,length is 100-1000 nm,and length-to-diameter ratio is about 10-35.TEMPO-mediated oxidation method can introduce carboxyl groups into the surface of t-TOCNs,which is one of a of useful methods introducing charge into cellulose surface;by extending the oxidation time of TEMPO-mediated system,the zeta potential of t-TOCNs suspension is-57.2 mV,which is better dispersed in water to form a stable suspension.The critical concentration of liquid crystals(LCs)formed in the t-TOCNs suspension was 4 wt%.As the concentration increases,the nomadic liquid crystal transitions to the chiral nematic liquid crystals(N*-LCs).When the concentration was 7 wt%,the N*-LCs fingerprint texture was observed with a pitch of 15.4 ?m.This is the first observation of the N*-LCs behavior of tunicate cellulose by TEMPO-mediated oxidation.N*-LCs can be observed in TEMPO-oxidized cotton cellulose nanocrystals(c-TOCNs)suspension obtained by hydrochloric acid hydrolysis and TEMPO-mediated oxidation system.The self-assembly of the c-TOCNs in the suspension takes some time to form a stable N*-LCs.By observing different concentrations of c-TOCNs,it was determined that the concentration of N*-LCs appeared in the concentrations of 8-20 wt%,and with the increase of the concentration,the pitch decreased gradually.In this thesis,using CNCs as a template,the cellulose/phenolic resin(CNC/PFR)composites were successfully prepared by the hydrothermal conditions for the first time.The analysis of POM,FT-IR,SEM,and TEM showed that the morphology and size of the composites can be controlled by controlling the ratio of CNCs and HMT and phenol.The carbon materials were obtained by carbonization at 800 °C,which have excellent electrochemical performance and stability.The specific capacitance of C-CNC/PFR 4:1 carbon material is greatly improved compared to C(64 F/g).When the current density is 1 A/g,the specific capacitance of C-CNC/PFR 4:1 carbon materials is as high as 157.2 F/g.It provides a very attractive way to produce high performance capacitive electrode carbon materials from renewable biomaterials.