Multistranded Structure of Polymerization-Induced <i>para</i>-Aramid Nanofibers and the Fast Untying Strategy toward Ultrafine <i>para</i>-Aramid Nanofibers

Although enormous success has been achieved under the well-known commercial name of Kevlar, the hierarchical refined organizational structure of high-performance para-aramid fibers of poly(p-phenylene terephthalate) (PPTA) still has a lot of mystery. Taking advantage of polymerization-induced self-assembly methods, we here demonstrate for the first time the multistranded ropelike structure of the original polymerization-induced para-aramid nanofibers (O-PANF). Based on the higher ordered structure, a simple but effective postuntying strategy is proposed to fast deconstruct the multistranded fibrillar “ropes” into ultrathin microfibrillar nanofibers (H-PANF) via less than 30 min treatment of O-PANF in an NMP/H2O/KOH solution system. In comparison with O-PANF (23.1 ± 7.6 nm), H-PANF (10.5 ± 5.5 nm) showed a smaller diameter and a more homogeneous distribution self-stabilized in aqueous dispersion. Using the H-PANF dispersion as the raw material, H-PANF paper was successfully prepared which exhibited obviously enhanced comprehensive performances including homogeneity, compactness, strength, thermal stability, electrical breakdown strength, and excellent durability. The excellent performance, the reduced operation complexity, as well as the fast and low-cost preparation process all make H-PANF paper a promising, scalable, and high-performance electrical insulation paper.