Synthesis and characterization of polyimides from diisocyanate with enhanced solubility and thermostability properties via direct low-temperature one-step polymerization in NMP solvent

Polyimides (PIs) can be synthesized from diisocyanate and dianhydride through a direct heating one-step polymerization process with a lower temperature and shorter reaction time than the traditional stepwise heating route. This study discusses the properties of resulting PIs produced using the direct one-step heating procedure with N-methyl-2-pyrrolidinone (NMP) as the solvent. Based on the structural and property evaluations, the reaction system used yields not only organo-soluble PIs but also ultra-high thermal stability up to 580 °C at 5% weight loss. The obtained PIs have medium molecular weights ranging from 26.6 to 35.6 kg/mol. This reaction system is found to be fast and efficient in producing high thermoresistant PI materials with improved processing ability. These findings provided insights on the energy-efficient one-step synthesis of PIs specifically derived from diisocyanate and dianhydride.