계면활성제를 이용한 실리카-산화철 나노복합소재와 실리카의 표면개질을 통한 폴리아미드이미드/실리카 하이브리드의 제조 및 특성 평가

Abstract

The nanocomposites are composed of multiphase solid materials. They includes not only particle type of composite materials but also, polymeric nanocomposites which contain well-dispersed nanoparticles in the comprehensive sense. These materials are advantageous due to their multifunction, and their properties can be designed into desired ones by controlling variables such as dispersion of fillers and so on. Attributed to the multifunction of the nanocomposites, these materials are applied to various fields, like catalyst, electrochemistry, medicine and so on. In chapter 1, as one type of nanocomposite particles, silica-hematite was introduced. In this study, silica-hematite (α-Fe2O3) nanocomposites were synthesized by addition of aqueous solution containing ferrous ions (Fe2+), cetyltrimethylammonium bromide (CTAB) as a surfactant and tert-butanol (t-butanol) as a cosurfactant into colloidal silica solution. At alkaline atmosphere, silica surface with negative charges electrostatically attracts positively-charged iron hydroxide nuclei or particles which are stabilized by cationic CTAB molecules, and then silica-iron compound composites could be formed. Finally, the silica-hematite composite particles were obtained after calcination at 800 °C for 4 hours. Through these processes, two types of composites having “core-shell type” or “decorated type” could be achieved. Morphology, Brunauer-Emmer-Teller (BET) surface area, crystallinity and magnetic properties of samples were analyzed by using transmission electron microscopy (TEM), BET, X-ray diffraction (XRD) and vibrating sample magnetometer (VSM), respectively. The “decorated type” composites had larger BET surface area and better magnetization. Also, to estimate the application in water treatment, adsorption properties of composites were studied through methylene blue (MB) adsorption which was characterized by UV-vis spectroscopy, involving collection of composites with neodymium magnet. In the chapter 2, the works related to polyamideimide (PAI)/silica nanohybrid was presented. In this work, an improved polymeric nanocomposite (PNC) preparation method was demonstrated associated with dispersion of fillers. PAI and silica nanoparticles were chosen as polymer material and fillers, respectively. To enhance the dispersion state of silica, 3-aminopropyltrimethoxysilane (APTMS)-functionalized silica prepared by sonochemical treatment was used. Gold-immobilization test was performed to confirm that APTMS grafted on silica with chemical bond, and UV-vis spectroscopy was used to detecting remained gold colloids. By this estimation, we could assure that APTMS-silica with chemically bound APTMS was obtained as a result of sonication. TEM was applied to observe the dispersion phase of silica, and enhancement of dispersion for PAI/APTMS-silica was proved. Then, to relate the dispersion with thermal stability of PNC, thermogravimetric analysis (TGA) was performed. With this analysis, we could confirm that thermal stability was improved associated with dispersion state of silica fillers. These researches can be helpful for the development of desired properties of the materials by controlling several variables, such as morphologies and so on. These studies can be applied as a facile and effective synthesis method.