Study On Synthesis And Charactorization Of Novel Multi-ketonic Polyimides And Its Copolymers

Aromatic Polyimides are well-recognized as high performance polymer materials. They are utilized in a wide range of military and commercial applications due to their unique combination of outstanding mechanical properties, thermal stability, good chemical and high-energy radiation resistance, and favorable economics. In order to explore the application in modern high technology fields, modifications proved as a successful method to obtained good comprehensive and processability materials. A novel dianhydride was synthesized based on the molecule design strategies. And then, a series of polyimides containing multi-ketonic moieties was synthesized by one-pot or two steps. The relationship between the structure and properties of the resulting polyimides were also investigated. This dissertation consists of three parts and as follows.1. A series of novel Multi-ketonic polyimides was prepared from 1,4-bis(3,4-diformic anhydride benzoyl)benzene and several aromatic diamines by two-stage process. The polymers were characterized by FT-IR, TGA and DSC. It shows that the multi-ketonic polyimides have high glass transition temperature and thermal stability. The average molecule weights of the resulting polymers affected by the concentration of poly-condensation and mole ratio of the monomers.2. A series of multi-ketonic polyimide was synthesized by 1,4-di(3,4-dimethyl benzoyl)benzene (p-DKDA) with 4,4'-methylenedianiline and 4,4'-diamino- diphenyl ether, through one-stage process, respectively. The polymers were characterized by FT-IR and DSC. It was indicted that the multi-ketonic polyimide has better thermal stability than the ones synthesized by two-stage process.3. Ternary copolyimide was synthesized by 1,4-di(3,4-dimethyl benzoyl) benzene (p-DKDA), pyromellitic dianhydride (PMDA) and 4,4'-diaminodiphenyl ether, through two-step process. The chemical structure of the copolymers was conducted by FT-IR. DSC and TGA results show that copolymers have the higher thermal stability, glass transition temperature, and increased by increased the mole ratio of pyromellitic dianhydride in the polymer main chain. The copolymers have good solvent resistance.