Preparation and properties of highly electrically conductive and heat-resistant crosslinked polyimide-polypyrrole

With the growing interest in high-temperature conductive applications, the demand for electrical conductive polyimides (PIs) has surged. However, the existing conductive PIs still remain challenges in achieving a balance between high conductivity and good thermal performance. To obtain PI simultaneously exhibiting superior conductivity and thermal properties, in this study, a diamine (5-POPDA) bearing pyrrole moiety was prepared and subsequently polycondensed with 4,4′-(hexafluoroisopropylidene) diphthalic anhydride (6FDA) to yield poly(amic acid) (5-POPPAA). After being ionized, the 5-POPPAA was combined with dopants and pyrrole monomers to create a suspension, which was subsequently put through an electrophoretic deposition procedure. In the procedure, the 5-POPPAA film was deposited, and simultaneous electrochemical polymerization occurred between suspended pyrrole monomers and pendant pyrrole groups of 5-POPPAA to form polypyrrole (PPy). This resulted in the crosslinked 5-POPPAA-PPy, which was chemical imidized to yield crosslinked 5-POPPI-PPy. The creation of extended π-conjugated PPy structure resulted in a large conductivity of 10.53 S/cm for 5-POPPI-PPy. Additionally, 5-POPPI-PPy demonstrated excellent thermal stability with 5 % and 10 % weight-loss temperatures (T_d5% and T_d10%) of 453 °C and 479 °C, respectively, benefiting from the covalent crosslinking between the 5-POPPI and PPy molecular chains. Moreover, the crosslinked 5-POPPI-PPy film exhibited good mechanical characteristics and remarkable high-temperature conductivity retention. While pure PPy lost its conductivity by being annealed at 250 °C, 5-POPPI-PPy retained a conductivity of 6.23 S/cm. This study offers insightful theoretical information for the development of conductive PIs tailored for conductive applications in high temperature.