| As one of the important characteristics of a solid surface, surface wettability has attracted great interests both in academic research and practical applications. In recent years, bifunctional interfacial materials with special wettability such as superhydrophobicity-superoleophilicity, superhydrophilicity-superoleophobicity, asymmetric wettability and stimuli responsive surface have attracted significant interest for their potential applications in oil/water separation, biosensor, microfluidic transmission, smart switch and biomedicine and so on. It was found that the special wettability of material surface was highly related to its chemical composition and microstructure. Therefore, to seek a convenient method or technology to change material surface chemical composition and microstructure of achieving its special wettability has important research significance. In this thesis, we select natural organic material chitosan which have rich sources and biodegradable as raw materials and successfully synthesized chitosan based sponges with different special wettability through simple synthesis and surface modification methods. We studied the surface wettability before and after modification and the relation between special wettability and chemical composition. The application performance of chitosan based sponges with different special wettability was also investigated. The main works are summarized as follows:1. Elastic chitosan sponge with three-dimensional porous structure was obtained by a simple vacuum freeze drying method. This sponge became superhydrophobicity superoleophilicity after modification with octadecanethiol. We studied the influence of the dosage of crosslinking agent on the sponge’s swelling rate, porosity and mechanical properties. We also investigated the oil absorption properties and absorption recyclability of superhydrophobicity-superoleophilicity chitosan sponge. The result shows that moderate crosslinking was beneficial to improve the porosity and mechanical properties of material. The maximum oil absorption capacity of the sponge is 60 times of their own weight. The sponge can be used to selectively absorb either floating oils on a water surface, or heavy oils under water and even emulsified oils in water, and the sponge shows excellence recyclability.2. Superhydrophilicity-oleophobicity Fe3O4/chitosan/melamine magnetic sponge was prepared by dip-coating method. Surface compositions of the sponges were analyzed by FTIR-ATR and XPS to discuss the mechanism of such special wettability. The selective adsorption capacity and oil/water separation performance of magnetic sponge was also investigated. The results show that water droplets are able to penetrate the surface because of water-molecule-induced rearrangement, and the 3D capillary effect caused by microstructure. In the presence of non-polar compounds, the interface is always occupied by the fluorinated constituents, resulting in surface with oleophobicity. The sponge can be quickly selective adsorption the water contaminants in the oil and can separate oil/water mixture effectively.3. Chitosan/starch composite sponge with porous structure was synthesized by a simple vacuum freeze drying method. After the modification of stearic acid, the sponge exhibit asymmetric wettability on its two sides:one side shows superhydrophobic and the other shows superhydrophilic. The effect of amount of starch on the asymmetric wettability of the sponge was studied, and the permeability and adhesion of bacteria on the chitosan sponge was also tested. The results showed that the addition of starch was favorable for the formation of asymmetric wettability, and with the increase of the amount of starch the water absorption rate of hydrophilic surface increased. The hydrophobic surface of the sponge exhibited anti-permeability and anti-adhesion for Escherichia coli and Staphylococcus aureus. Chitosan/starch composite sponge with asymmetric wettability has the potential applications as a medical wound dressing. |
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