| It is well known that the petroleum resources will be exhausted after seventy years, and the problem of environmental pollution from the waste of nondegradable synthetic polymers that are mainly derived from petroleum resources becomes more and more serious. Therefore, polymer science and technology faces new challenge. Because the renewable natural polymers from animal, plant and microorganism could possibly replace the traditional raw materials of chemistry industry in the future, the research and exploitation of new materials based on natural polymers has become one of the frontiers of polymer science in 21 century. Chitin is the most important marine biomass resource, with a huge annual production of 150,000 ton, and easily accessible from crustaceans and insects. The principal derivative of chitin, chitosan, is obtained by N-deacetylation of more than 55%. The utilization of chitin and chitosan as materials has been challenged by some limitations, because of their intractable nature and high brittleness. However, abundant hydroxyl and amine groups exist in chitin and chitosan, so the physical and chemical modifications of chitin and chitosan are available. Polyurethane is a kind of elastomer that form polymer network easily, and the blend films from polyurethane and natural polysaccharides can be degraded by microorganisms. Semi-interpenetrating polymer networks (semi-IPN), a kind of polymer blends held together by permanent entanglement between a cross-linked polymer and a linear polymer, has drawn attention as a result of improvement of mechanical properties brought by interlocking of polymer chains. The main contents of this thesis include the preparation and research of novel ecomaterials with the method of IPN, characterization of IPN composite materials by using advanced apparatus and new methods, and study the relationship between composition, structure, miscibility, interfacial interaction and properties of the blend films. The creative achievements of this thesis are as the follows. (1) Carboxymethylated chitin (CMCH) has been synthesized by a modified method, and mixed with waterborne polyurethane (WPU) to prepare a series of blend films exhibiting excellent mechanical properties of tensile strength, thermostability and organic solvent resistance. (2) It has been clarified for the first time that the hydrophility and hydrophobility of the solid substrate significantly influenced the structures and properties of the casting semi-IPN films from CMCH and WPU. It has been confirmed that the films prepared on the Teflon as the substrate possessed better miscibility and higher storage modulus, thermal stability, tensile strength and solvent-resistance. (3) Two series of semi-IPN materials based on amorphous nitrochitosan (NCH) and semicrystalline poly (ester-urethane) (PU) have been first prepared. It was revealed that with an increase of NCH from 5 to 30 wt%, the thermalstability, tensile strength and water resistance of the blend films cross-linked with cross-linker tris (hydroxylmethyl) propane (TMP) increased on the whole. (4) The effects of reaction temperature and cure temperature on the crystallization behavior, morphology and mechanical properties of semicrystalline PU have been clarified. The PU synthesized at 100 C and cured at 60 C exhibited excellent tensile strength and breaking elongation. (5) The elastic materials based on amorphous NCH and semicrystalline PU have been successfully prepared. The effects of cure temperature on the structure, crystallization behavior and mechanical properties of the composite materials have been clarified.The main research contents and conclusions are divided into the following parts. CMCH was synthesized by a modified method, and mixed with WPU in aqueous system to prepare a series of blend films cast on glass plate. The miscibility parameters of the WPU/CMCH aqueous solution obtained by dilute solution viscometry (DSV) predicted that the blend of WPU and CMCH was miscible or partially miscible over the entire composition range. As CMCH content i...
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