Preparation Organic/Inorganic Nanocomposites Via A SC CO₂-assisted Process

With the rapid development of nano-science and nano-technology in recent years, nanoscale building organic/inorganic nanocomposites with the controlable structure and unique functions has become a hot topic in the field of materials research. Compared with the general composite materials, the performance of organic/inorganic nanocomposites has been greatly improved in mechanical properties, electrical properties, optical properties and thermal properties. There are very strong interactions between the inorganic phase and polymer interface in the nanocomposites. Because of environment friendliness, chemical inertia, non-toxicity, non-flammability, cheapness, low viscosity, and low critical temperature and pressure (31.0℃,7.38 MPa), supercritical CO2 (SC CO2) is the most preferable supercritical medium used in environmental management, chemical reactions, material preparation and other fields. The issue prepared a series of organic/ inorganic nanocomposites via a SC CO2-assisted process. In this study we not only create a new method of polymer modification, but also provide a new way to design and develop high-performanced as well as multi-functional organic/inorganic nanocomposites. The main contents are as follows:(1) The issue prepared a kind of functional organic and inorganic (MDMO-PPV/SWNTs) nanocomposites via a SC CO2 anti-solvent technology, and explored the relationship between the experimental conditions of SC CO2 and the microstructure and properties of nanocomposites.(2) Under the condition of SC CO2, the Pd nanoparticles were being generated in situ on the surface of CNFs by reducing a palladium precursor with ethanol. Then a type of wonderful hierarchical structure containing inorganic CNFs or CNTs, organic polymer, and inorganic metal nanoparticles, as PE/CNFs/Pd and PVA/CNTs/Pd was built successfully.(3) The issue has developed a simple supercritical CO2-assisted synthesis of Pd nanoparticles, in which Pd nanoparticles can be readily generated in situ on colloidal spheres by reducing a palladium precursor with ethanol.In preparing MDMO-PPV/SWNTs nanocomposites, we attribute this effect of SC CO2 to the following reasons:on the one hand, as the experimental pressure rises, the viscosity of the medium decreases because of dissolving more CO2, and thus it facilitates MDMO-PPV chains wrapping on CNTs. On the other hand, due to the antisolvent effect of SC CO2, there is transition of conformation of polymer chains with different polymer-solvent interactions.In preparing Pd nanocomposites, we also attribute this effect of SC CO2 to the following reasons:on the one hand, as the experimental pressure rises, the viscosity of the medium decreases because of dissolving more CO2, and thus it facilitates MDMO-PPV chains wrapping on CNTs. On the other hand, due to the antisolvent effect of SC CO2, there is transition of conformation of polymer chains with different polymer-solvent interactions.The metal precursor (PdCl2) could spread around the carrier conveniently and evenly, on which PdCl2 could be reduced. On the other hand, the crystals growed more likely due to the antisolvent effect of SC CO2.