Preparation And Property Study Of Nanocrystalline Cellulose Cholesteric Liquid Crystal, Film And Oxide

Cellulose is a polymer material that widespread in nature. It can be easily modyfied due to alargr number of hydroxyl existing in its molecular structure. Nanocrystalline cellulose (NCC)cholesteric liquid crystal film is a kind of modified material that both with the chemicalproperties of cellulose and optical selective reflection light property of cholesteric liquid crystal.Dialdehyde cellulose (DAC) is a product of selective oxidation by periodate. It can interact withthe amino groups of biological molecules and form a Schiff base because of the presece ofaldehyde, so it can be used as the antibody carrier. The "lable-free" detection ofantibody-antigen-specific immune can be achieved through deceting the change ofnanocrystalline cellulose cholesteric liquid crystal film's reflection wavelength before and afterthe combination of antibody and antigen.The specfic work carried out in this paper are follows:(1) Preparation an characterization of nanocrystalline cellulose suspension: a series ofcellulose suspension were prepared in different acid concentration, time, temperature conditionswith cotton cellulose filter paper, sulfuric as raw materials. The final samples were characterizedby polarized optical microscopy (POM), differential scanning calorimetry (DSC), Malvern laserparticle size analyzer, transmission electron microscopy (TEM), surface sulfur content testing.The results showed that: the best reaction condition of the preparation of nanocrystalline celluloseas follows: the sulfuric acid concentration was64%, the reaction temperature was60℃, reactiontime were0.5h-2.5h. The particle size was about100nm and homogeneity with higher surfacesulfur content under these conditions.(2) Nanocrystalline cellulose suspension cholesteric phase behavior: the best preparednanocrystalline cellulose suspension in the previous step were characterized under polarizingmicroscope in flat capillaries to observe the liquid crystal, the formation of cholesteric liquidcrystal, critical concentration, the pitch size and the change of the pitch. The observations showthat: with the evaporation of the water, the fingerprint texture, the characteristic structure ofcholesteric liquid crystal, will precipitate from the isotropic phase and submerge in the bottom. Atthe same time, the pitch decreases gradually; Surface sulfur content was important to theformation of cholesterol liquid crystal. The higher the surface sulfur content, the smaller the pitchwhen the suspensions were at the same concentration.(3) Rapid preparation of nanocrystalline cellulose films under vacuum: a series ofnanocrystalline cellulose films which possess selective reflection properties of cholesteric liquidcrystal were quickly prepared with the suspension prepared at60℃, acid concentration64%,2.5h as raw material under different vacuum degrees in order to accelerate the evaporation of water.The films were characterized by polarizing microscope (POM), UV-visible spectroscopy(UV-vis), atomic force microscope (AFM), scanning electron microscopy (SEM). The resultsshowed that: the vacuum degree affected the adequacy of the charged cellulose particles' orderlyarrangement in the nanocrystalline cellulose suspension through impacting the evaporation rate.The maximum reflection wavelength of the nanocrystalline cholesteric cellulose films redshiftedwhen the vacuum degree increased.(4) Preparation and characterization of nanocrystalline dialdehyde cellulose: nanocrystallinedialdehyde cellulose were prepared with sodium periodate, nanocrystalline cellulose suspension64%,60℃,2.5h as raw material, and oxidant, oxidation time as a variable. Infrared (FT-IR), aseries of TG and other characterization showed that the performance of nanocrystallinedialdehyde cellulose reach optimal when the mass ratio of oxidant and nanocrystalline cellulosewas2:1, oxidation time was3h.