Preparation And Properties Of Liquid Crystals From Tunicate Cellulose

Cellulose is one of the most abundant renewable biological resources in the world, so it has been paid much attention to and widely investigated by researchers. Tunicates are the only sea animals known to produce cellulose in their tunic.In this thesis, styela clava and Halocynthia roretzi, two kinds of ascidian, were used as raw materials to extract cellulose by being soaked in alkali solution and bleached. Tunicate cellulose nanocrystals (t-CNs) were prepared by acid hydrolysis of the cellulose extracted from the two kinds of ascidian. The t-CNs was characterized by using thermo gravimetric analyzer (TGA),Fourier transform infrared spectrometer (FT-IR), X-ray diffraction(XRD), polarizing optical microscope (POM), scanning electron microscope (SEM), atomic force microscope (AFM) and Malvern particle size analyzer.The results indicate that the thermal stability of cellulose from styela clava and Halocynthia roretzi was similar but higher than that of cellulose from cotton.The crystallinity degree of t-CNs was higher than that of the origin cellulose extracted from the two kinds of ascidian about0.6%and the rate of thermal decomposition temperature of t-CNs stepped down. Also, the initial decomposition temperature was slightly shifted to the lower side. However, the thermal stability of t-CNs at high temperature region was improved.The acid hydrolysis process has a more obvious impact on the thermal stability of cotton cellulose compared to tunicate cellulose. It was found that t-CNs suspensions self-organized into spectacular liquid crystalline arrangements was concerned with the size of t-CNs. POM observation revealed that lyotropic chiral nematic liquid crystals (N*-LCs) could form and the pitch of the N*-LCs was about15μm when the concentration of suspension was about5.0wt%. The pitch has not changed by prolonging the hydrolysis time for21.5h.In this thesis, cotton cellulose nanocrystals(c-CNs) were prepared by acid hydrolysis. The morphology and size of c-CNs were researched by POM, TGA, SEM, FTIR and AFM. Then, the influence of concentration of the c-CNs, magnetic field and ultrasonic treatment on helical pitch of the N*-LCs were studied. The results indicated that the fingerprint texture of the N*-LCs of c-CNs was observed when the concentration of the c-CNs was higher than3.0wt%, but disappeared when the concentration was increased to6.0wt%. The pitch has linear change along with the increase of the suspension concentration of c-CNs. Magnetic field increased the upper critical concentration for disappearing fingerprint texture, but it had little influence on the pitch. Ultrasound treatment increased the dispersion of c-CNs in the water, obtained better transparency suspension, and also increased the critical concentration of c-CNs to form N*-LCs.Lyotropic N*-LCs of CNs could be evaporated to produce solid semi translucent N*-LCs films that retain the self-assembled helical order formed in the lyotropic N*-LCs. In this thesis, the N*-LCs films that can selectively reflect light with specific wavelengths were prepared by drying the lyotropic N*-LCs. Then POM and UV-vis-NIR spectrophotometer were used to study the optical properties of the films. The results indicated that ultrasound treatment induced red-shift in reflection wavelength of the films and increased the size of the chiral nematic domains. The vacuum degree also can induce red-shift in reflection wavelength of the films.In this thesis, spinning dope was prepared from tunicate cellulose by using different solvent. The results indicated that tunicate cellulose could be dissolved in l-methyl-3-methyl imidazole chloride and lithium chloride/dimethyl acetamide respectively.