Polyimide wide variety of forms. According to incomplete statistics, it has been used to synthesize a polyimide dianhydride and diamine reached 200 to 300 kinds, Therefore, the synthesis and study of polyimide has reached thousands. At the same time the synthesis of polyimide in several ways, it can be selected according to various application purposes. Continuity on variable such synthetic polymer is difficult to have the other.
Polyimide main dibasic anhydride and diamine synthesis, these two monomers and many other heterocyclic polymers, such as polybenzimidazole, polybenzoxazole, polybenzthiazole, polyquinoline monomer such relatively wide source of raw materials, synthetic and easy.
The polyimide may be composed of a diamine and a dianhydride in a polar solvent, such as DMF, DMAC, NMP, or THF / methanol mixed solvent of low temperature polycondensation to obtain a soluble polyamic acid, filming or spinning and then heated to about 300 ℃ dehydration ring into polyimide; It may also be added acetic anhydride and tertiary amine catalysts such as polyamide acid, the chemical dehydration cyclization to the polyimide solution or powder. Dianhydride and the diamine may also be in a high boiling solvent, such as phenolic solvent to provide polycondensation step to obtain a polyimide. In addition, it may be made of dibasic esters and diamine tetra-acid obtained polyimide. It can also be made of polyamide acid into polyimide polyisoprene. Then heat into polyimide. These methods have brought convenience for the processing, the former is called PMR method, you can obtain a low viscosity solution, high solid content, when formed with a window having a low melt viscosity, particularly suitable for the manufacture of composite materials in; Increase the solubility of the latter in the process of transformation does not release low molecular weight compounds.
Just anhydride (or four acid) and diamine purity qualified Regardless condensation method, are easy to obtain sufficiently high molecular weight; Join unit glycoside or amine unit also can easily regulate the molecular weight.
Low molecular polyimide containing anhydride (or ortho acid) end groups and amine end groups can react with each other when heated under vacuum, the relative molecular mass continued to increase.
Easily introducing a reactive group at the chain end or a chain to form an active oligomers to obtain a thermosetting polyimide.
Use polyimide acid carboxyl group, esterification or salt formation, the introduction of photosensitive groups or long-chain alkyl obtain amphiphilic polymers obtained photoresist, or hybrid material for the preparation of LB films.
General synthetic process of polyimide not produce inorganic salts which the prepolymer solution or the polyimide coating or spinning may be used directly, without the need for complicated washed to remove inorganic salts can degrade performance-product, which is particularly advantageous for the preparation of an insulating material.
As a dianhydride and a diamine monomer is easily sublimated under high vacuum, and therefore can be used a polyimide film vapor deposition method is formed on the workpiece, in particular having sharp edges or surface irregularities of the device.