| As a kind of natural polymer, cellulose nanocrystals (CNCs) have the property of forming strong hydrogen bonding due to their surface hydroxyl. CNCs can form good affinity, overlap and synergy with supramolecular system based on hydrogen bonding, so as to improve the reactivity of composite materials and provide the composite materials more special features. Based on the nature of hydroxyl, CNCs can be decorated by supramolecular system with multiple hydrogen bonding or host-guest interaction. The cellulosic nano-structure is oriental designed and tailored at the molecular level, so all kinds of active groups can be grafted to the surface of cellulose, on which advanced functional cellulose materials can be obtained. A lot of researches have been devoted to prepare cellulose nanocrystals, but these methods have some drawbacks such as complex process, low yield and environmental pollution. To overcome these disadvantages, CNCs were prepared with a high yield by simultaneous mechanochemical activation and phosphotungstic acid hydrolysis in this dissertation, and the process is green and high-efficiency. Based on the nature of hydroxyl, CNCs were decorated orientally, and then the supramolecular system with special structure was inserted into the surface of CNCs to create intelligent hydrogels and membrane material based on the laws of multiple hydrogen bonding and host-guest interaction. The main achievements are as follows:1. The preparation method of mechanochemical process with the catalyst of phosphotungstic acid is simple and environmentally-friendly, leading to a high yield of cellulose nanocrystals. The results show that mechanochemical process enhanced the reaction activity of cellulose and improved effectively the hydrolysis efficiency. Under the optimal conditions, a high yield of up to 88.4%, crystallinity index of 79.6%, length of 200-300 nm and width of 25-50 nm can be achieved.2. CNCs/sticky rice lime mortar hybrid material was created by the combination of CNCs and sticky rice lime mortar. The results show that the surface hardness, compressive strength and freeze-thaw resistance properties of the hybrid material were significantly improved with the addition of CNCs. The fundamental cause of the excellent properties of hybrid material lies in the regulation of CNCs for the biomineralization process. The size, morphology and structure of calcium carbonate were regulated by CNCs, leading to the enhancement of binding force among different components in the hybrid material.3. The surface chemical modification of CNCs was conducted by the group of-UPy to form CNC-UPy, and then the obtained CNC-UPy was combined with PVA to create supramolecular composite membrane with strong mechanical properties. The characterization results of morphology, thermal stability and mechanical properties of supramolecular composite membrane show that CNC-UPy was homogeneous dispersion in PVA and the aggregation of CNC-UPy was not found. The multiple hydrogen bonding between CNC-UPy and PVA was formed and led to the improvement of interfacial compatibility, so as to improved the thermal stability and tensile strength of supramolecular composite membrane.4. pH responsive hydrogel based on cellulose was prepared by hydrogen bonding between cellulose and gelatin under the dissolve system of cellulose with potassium thiocyanate/ethidene diamine. The FESEM, XRD and NMR results show that the strong hydrogen bonding between cellulose and gelatin was formed and the obtained composite hydrogel was sensitive to pH.5. Temperature responsive supramolecular hydrogel based on cellulose was created by host-guest interaction and hydrogen bonding. During the formation of supramolecular hydrogel, cellulose was dissolved in the alkaline solution firstly and then grafted with β-CD to form inclusion compound with polypropylene glycol. The results show that the supramolecular hydrogel was reverse temperature sensitive, and the LCST was 34℃. |
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