Topologicity-Dependent Spinning and Phase Separation toward High-Performance Polyetherketoneketone Fibers

High-performance thermoplastic fibers are very important in widespread applications owing to their excellent mechanical and thermal properties. However, for advanced engineering thermoplastics, melt processing meets severe problems of high melting point and high melt viscosity, and there is a lack of efficient wet spinning due to high indissolubility. Here, we report a novel topologicity-dependent processing for poly(ether ketone ketone) (PEKK), including dissolution, spinning, phase separation, and structural stability. With the randomly appearing para- and meta-positioned ketone groups and high chain rigidity as well, PEKK shows a strong entanglement, namely, molecular locking even after dissolution. Such locking is the real source of spin flexibility, especially for low-concentration solutions. It also causes a special phase separation from which highly porous fibers are spun. By reducing the phase separation rate to realize the overall condensation and a consequent hot stretching, solid fibers with high strength (516 MPa) and stiffness (6.13 GPa) are prepared. PEKK fibers do not show evident viscoelasticity and are mechanically stable within a temperature range of – 196–300 °C, as the topological locking hinders the reconstruction of chain condensation. The locking also retards flame by avoiding chain disassembling. This work provides a new strategy to process thermoplastics by introducing topological structure into polymer chains.