| Properties of materials strongly depend on not only their chemical structures but also their micro-structures. The chemical structures decide the chemical properties, and the micro-structures including micro-morphologies, molecular orientations and crystal structures. So the developments of new chemical structures or special micro-morphologies will promote the development of new functional materials.As a kind of traditional special engineering plastics, polyimides (PI) have been exploited as merchandises in the forms of films, dopes, fibers, foams and adhesives etc. owing to their excellent thermal, mechanical and dielectric properties. As a kind of bulk-materials, polyimides were exploited as a kind of matrix resin to make composite materials with polymers, carbon fibers, glass fibers and inorganic particles, while there were few works on micro- or nano- polyimides. With the developments of nanotechnology, how to process this kind of high-performance engineering plastics into functional nano-materials becomes an urgent demand. So a variety of nano-materials based on polyimides have been fabricated, such as particles, sheets, LB films, fibers, micelles, hollow spheres and so on.Therein, the PI-based micro- and nano- spheres have attracted more attention for their large specific surface area which would enlarge the dispersibility in ordinary organic solvent even in water, thus they can be fabricated for waterborne polyimide materials. Polyimides micro- and nano- spheres will broaden the temperature range of polymer micro- and nano-spheres. The polyimides hollow spheres have potential applications in low dielectric materials, high-temperature nano-containers and confined reaction vessels with heat resistance, etc., combining both the excellent thermal performances of the polyimides and the advantages of hollow structures. Furthermore, the polyimides hybrid hollow spheres can endure the materials more use as conductive hollow spheres or magnetic hollow spheres.Herein, we report a facile and general preparation of PI hollow spheres with uniformly controllable sizes using highly cross-linked sulfonated polystyrene gel (SPS) hollow spheres as the templates. On one hand, the hollow template-assistant synthesis can avoid the fracture brought by core-sacrificed method. On the other hand, sulfonated polystyrene gel shell is infiltrative favoring polyimides precursors (PAA) to penetrate into the shell and form desired configuration with specific interaction. Moreover, the highly cross-linked hollow spheres can maintain the spherical contour during the template synthetic process to make the polyimides composite hollow spheres possess the same shape as the original hollow spheres. Two kinds of polyimides have been chosen to confirm the general utility of this method. One is a kind of macromolecular, which has the same structure of Upilex-R films; while the other one is a kind of oligmer. The transmission electron microscopy (TEM) and scanning electron microscopy (SEM) images revealed that the obtained particles were kinds of quasi-closed-hole polyimides-C (PI-C) composite hollow spheres without connecting, which had potential applications as heat preservation, thermal insulation and sound-absorb materials. Comparing with the template hollow spheres, the polyimides hollow spheres had rough surfaces and thicker shells, and the existence of polyimides was verified by FT-IR spectra. We calculate the weight ratio of polyimides according to the element analysis of N. The resulting hollow spheres exhibited good dispersibility in water or ethanol.Based on the preparation of poly (amic acid)s hollow spheres, we took use of the inorganic nanoparticles to fabricate polyimides hybrid hollow spheres. Firstly, we prepared Ag@PI composite hollow spheres by taking in-situ adsorption and reduction processes of Ag+, and compared the differences of Ag nanoparticles prepared under different conditions. The crystal structures of Ag particles were characterized by XRD, and the weight ratios of Ag on the spheres were calculated according to the remaining in air atmosphere after TGA tests. And then we prepared the Fe3O4@PI composite hollow spheres through in-situ adsorption and chemical coprecipitation method. The resulted magnetic particles turned out to be a mixture of iron oxide nanoparticles. Both XRD and SAED patterns verified the orthorhombic structure of Fe3O4, and the TGA testing result gave the theoretic weight ratio of Fe3O4 on the composite hollow spheres. Besides, we took use of the penetration and hydrolysis condensation process of TEOS to prepare SiO2/PI composite hollow spheres. By changing the concentration of TEOS, we got different SiO2/PI composite hollow spheres with varying content of SiO2. After being heated in the air, the composite hollow spheres changed into the SiO2 hollow spheres with exactly the same shape of polymer hollow spheresAn interesting phenomenon that the polyimides hollow spheres possess good dispersibility in water or ethanol in our former works attracted us immediately. How to fabricate waterborne polyimides in simple way becomes a thesis which we work on. Spray drying is a simple, cheap, and environmental conservation technique which has been widely used in manufacturing process. It`s a kind of inexpensive process which causes less pollution by tight protection and solvent reusing system and to produce pure product. In recent years, particle engineering has been used to design complex particles which meet the demands for micro- or nano- materials. In this thesis, we prepared water-dispersed poly(amic acid)s particles without any surfactant, and the morphologies of particles varied with the chemical structures of polymers, while the temperature played a lesser role. The soft chains gave the particles spherical contours. The resulting polymer particles exhibited a good dispersibility and re-dispersibility in water, and could form flat films after thermal imidization, which implied that the particles can be expoited as a kind of new practical waterborne polyimides. The spray method was proved to be a promising technique to fabricate polyimides micro- and nano-spheres while keeping the chemical structures of polymers.
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