Study On Preparation And Properties Of A Novel Polyimide/Ceramic Spheres Hybrid Films And Polyimide/Ag Hybrid Films

Organic/inorganic hybrid materials usually have unique properties that traditional composites and conventional materials do not have. They may combine the advantages of the organic polymers (flexibility, ductility, dielectricity and processability) and the inorganic materials (rigidity, high thermal stability). Furthermore, organic/inorganic hybrids often exhibit some special mechanical, electronic or optoelectronic properties, which extend their applications to many new fields. As a high performance polymer material, polyimide (PI), which exhibits outstanding dielectric, mechanical properties, thermal stability, low coefficients of thermal expansion (CTEs) and unique properties in preparation of hybrids has become an indispensable material for microelectronics and aircraft areas. And it is paid more attentions now. There are lots of reports of hybrid materials prepared from PI and inorganic materials. Lots of inorganic materials, such as ceramic materials, polysiloxane, molecular sieves, metal powders, metallic salts, metallic organic compounds and so on, can be used to prepare PI/inorganic hybrids. Inorganic materials usually distribute in the PI matrix as the dispersed phase.But in most of the previous works, most attention was focused on how to make the inorganic materials disperse more homogeneous in the organic matrices and how to reduce the phase separation between the organic and inorganic phases. The hybrids prepared previously were only the ones with inorganic materials dispersing homogeneously in polymer matrices. So we expect to prepare certain hybrids with different inorganic particles distributing heterogeneous in matrices (for example, the inorganic particles distributing on one side of the polymer matrices), and want to find whether this kind of hybrids would have new potential properties and applications. We also want to develop a new research area for our team.Firstly, PI/ceramic spheres hybrid films with ceramic spheres distributing on one side were prepared via controlling the sedimentation of ceramic spheres in a polyamic acid (PAA) solution in a gravitational field and the conditions which affected the sedimentation of ceramic spheres were studied by scanning electron microscope (SEM), and a theoretical model and corresponding interpretations were put forward. The results showed that the conditions included the diameter of the ceramic sphere, the density of the ceramic sphere, the viscosity of PAA solution, the density of PAA solution, the time ceramic sphere had sedimentated for, the volatilizing velocity of solvent (different volatilizing velocity of solvent in close and open system respectively). Close system was propitious to the sedimentation of spheres. The thermal properties of hybrid films were investigated by differential scanning calorimeter (DSC) and thermal gravimetric analyzer (TGA). Moreover, their mechanical properties were also characterized. The results showed that the thermal stability was enhanced by the addition of the ceramic spheres and the mechanical properties retained effectively.Then the ceramic spheres were dissolved away by dilute hydrofluoric (HF) acid to obtain macroporous PI films with pores distributing on one side. The morphology and densities of macroporous PI films were studied to prove the fabrication of pores and the pores were distributing on one side. Only when the ceramic spheres have sedimentated completely to bottom side of the hybrid films, high-quality macroporous PI films can be prepared. The thermal and mechanical properties of porous films were studied by DSC, TGA and universal tester. It has been proved that the thermal and mechanical properties of macroporous PI films retained effectively.At last, PI films containing silver nanoparticles in pores distributing on one side were fabricated via immerging Ag(NH3)2+ into macroporous polyimide films followed by deoxidizing with glucose as reducing agent. SEM, EDX and XRD analysis was carried out to reveal the presence and morphology of Ag nanoparticles, confirming the incorporation of Ag within the macroporous PI films. The undersurface composition and the mass percentages of Ag were determined by XPS and Plasma Emission Spectrometer, respectively. Also, the thermal and mechanical properties of PI/Ag hybrid films were studied by DSC, TGA and universal tester. It has been proved that the thermal and mechanical properties of PI/Ag films retained effectively. Further investigations onto the functionality of these films are now in progress.