Diamines are organic compounds containing two amino groups (-NH2) and are important building blocks for the synthesis of polyimides. They react with dianhydrides to form polyimide polymers through polycondensation, resulting in high-performance materials. Polyimides derived from diamines have excellent mechanical properties, high thermal stability, and good chemical resistance. Due to the robustness of polyimide polymers, diamines are widely used in the aerospace, automotive, and electronics industries. Common diamines include aromatic diamines such as 4,4'-oxydiphenylamine and 4,4'-diaminodiphenylmethane, which are essential in the production of polyimide films and composites.