Polyimides are of particular interest in the preparation of hybrid materials, especially for the sol-gel process, which is widely used.
1. Polyimide is by far the most widely used polymer material in the industry, its high thermal stability and high glass transition temperature is very beneficial for the synthesis of hybrid materials.
2. Polyimide can be synthesized through a variety of ways, such as polyamic acid, polyamide acid salt, polyamide resin, polyisocyanate and so can be used as a precursor of polyimide. Their common feature is greater solubility in organic solvents, hybrid materials can be selected according to the need to prepare the appropriate precursor.
3. Polyamic acids are most commonly used in the preparation of hybrid materials because they can be obtained by polycondensation of dianhydrides and diamines in aprotic polar solvents. These solvents are also good solvents for many inorganic precursors. Polyamic acid in a very high water content of non-proton polar solvent can still be dissolved, which is sol-gel method and the metal dopant to bring the convenience of the hydrolysis condensation. The carboxyl group of the polyamic acid interacts with the inorganic species or its precursors, such as salts and esters, to provide ready-to-use conditions. This combination of molecular levels stabilizes the dispersion of inorganic nanoparticles. Water generated during polyamidation sometimes also plays a key role in the formation of inorganic phases.