Abstract
Polyimides (PIs) are a class of representative high performance polymers possessing the cyclic imide and aromatic groups in the main chains. Since the first polyimide, Kapton H (developed by DuPont in the 60s), many other polyimides with modified properties were developed and commercialized. At present they are extensively used in microelectronics, photonics, optics, and aerospace industries not only for their considerably excellent thermal stability but also for their good mechanical properties, low dielectric constant, low coefficient of thermal expansion, and high radiation resistance. Significant effort has been expended to improve their properties further by chemical modification of the chain backbones and higher order structure control.