Consecutive large-scale fabrication of surface-silvered polyimide fibers via an integrated direct ion-exchange self-metallization strategy

Herein, we report our success on the large-scale online preparation of surface-silver-metallized polyimide (PI) fibers by utilizing silver ammonia complex cation ([Ag(NH3)2](+)) as the silver (Ag) precursor and pyromellitic dianhydride/4,4'-oxidianiline (PMDA/4,4'-ODA)-based polyimide as the matrix via a direct ion-exchange self-metallization process integrated within a consecutive fiber-spinning procedure. The method works by using the online freshly prepared PMDA/4,4'-ODA-based poly(amic acid) (PAA) fibers as the starting material to perform an ion-exchange reaction in aqueous silver(I) solution to load silver(I) into the PAA precursor fibers, followed by a programmed stepwise thermal treatment process to convert PAA to its final imide form with the concomitant silver(I) reduction and the subsequent aggregation, producing the surface-silvered polyimide hybrid fibers. The influence of thermal cycles on the formation of silver nanostructures, and the variation of surface morphologies and fiber properties during the heating process were investigated. Experimental results indicate that the PI-Ag fibers were produced with good mechanical and thermal properties. In addition, bioassessment suggests that the hybrid fibers exhibit superior antibacterial activities (99.99% in 24 h toward E. coli ). Outstanding electrical conductive properties of a certain length of the PI-Ag hybrid fiber (electrical resistance: ca. 0.1 Ω cm(-1)) could also be realized on the composite fibers but with severe destructions in the final mechanical properties. The fibers were also characterized by FTIR, ICP, XRD, SEM, and TEM.