Research on N,N′‐carbonyldiimidazole: A novel low‐temperature imidization accelerator of polyimide

Abstract High imidization temperature of polyimides (PIs) brings great restriction to the applications in electronic industry. In this study, N,N ′‐carbonyldiimidazole (CDI), a novel low‐temperature imidization accelerator with the unique dual function of catalyst and dehydrating agent, was researched to solve this problem. PIs synthesized from 4,4′‐(hexafluoroisopropylidene)diphthalic anhydride (6FDA) and 4,4′‐oxydianiline were researched as the main object on method A and method B, two preparation methods of PIs, by introduction of CDI, which was found that the PIs prepared by method A achieved complete imidization and basically had no residual CDI and N,N ‐Dimethylacetamide at 180 °C under vacuum, while the completely imidized PIs prepared by method B were also obtained at 40 °C. Even prepared at low temperature, the PI films with adding CDI both showed satisfactory thermal and mechanical properties, especially in reducing coefficient of thermal expansion. In addition, the universality of the reaction between CDI and poly(amic acid) were also verified by other soluble PI systems. All these results prove the superior performance of CDI in lowering imidization temperature, showing great potentials in low‐temperature cured PIs.