Study On The Preparation And Properties Of Nanoporous Polyimide Based Materials

At present, with the rapid development of Electronic Information Technology, electronic products are also developing to the direction of light weight, thin, high performance and multi-functions. The development of electronic products proposes high requirements on the performance of dielectric materials. Nanoporous materials with large specific surface area, relatively uniform pores, and special channel, have been widely used in dielectric, optical, magnetic, new energies, chemical industry, bioengineering and other fields. Every year, many literatures about the recent research results in this field are introduced on the world’s top academic journals.In this paper, the template method by the removal of polyimide matrix porogenic agent to prepare nanoporous polyimide films was given. First, Porogens with certain size were prepared by emulsion polymerization method. Four factors (i.e. initial content of monomer, emulsifier, initiator, and alcohol water ratio) were discussed in the orthogonal experiments design process. The effects of the factors on pore sizes and morphology of porogens were investigated. Next, Liquid phase mixing method was applied to introduce the porogen into the polyimide precursor. Porogens were then removed with high temperature in the process of the imidization. Here we discussed the effects of different content of porogen on the polyimide film porosity, surface morphology, thermal stability and dielectric properties.SEM results showed that the prepared porogen particle size was about50-300nm with a smooth surface, good sphericity and monodispersion. According to the TG-DSC analysis of the porogens, it indicated that the porogen decomposed from180℃to450℃, which ensured that the thermal decomposition method can removed the porogen from the matrix and get the nanoporous polyimide films. The polyimide film had nanoporous structure, and in a certain range of size. With the increase of mass fraction of porogen, the number of polyimide film holes (porosity) increased. While the mass fraction of porogen exceeded a certain value, the number of the holes of the porous polyimide films decreased. This phenomenon was also showed with the dielectric constants. The thermal stability of polyimide film with different mass fractions of porogen presents no large difference.