Ambient Catalytic Spinning of Polyethylene Nanofibers

A novel single‐atom Ni(II) catalyst (Ni‐OH) is covalently immobilized onto the nano‐channels of mesoporous Santa Barbara Amorphous (SBA)‐15 particles and isotropic Anodized Aluminum Oxide (AAO) membrane for confined‐space ethylene extrusion polymerization. The presence of surface‐tethered Ni complexes (Ni@SBA‐15 and Ni@AAO) is confirmed by the inductively coupled plasma‐optical emission spectrometry (ICP‐OES) and X‐ray photoelectron spectroscopy (XPS). In the catalytic spinning process, the produced PE materials exhibit very homogeneous fibrous morphology at nanoscale (diameter: ~50 nm). The synthesized PE nanofibers extrude in a highly oriented manner from the nano‐reactors at ambient temperature. Remarkably high Mw (1.62×106 g mol−1), melting point (124 °C), and crystallinity (41.8 %) are observed among PE samples thanks to the confined‐space polymerization. The chain‐walking behavior of surface tethered Ni catalysts is greatly limited by the confinement inside the nano‐channels, leading to the formation of very low‐branched PE materials (13.6/1000 C). Due to fixed supported catalytic topology and room temperature, the filaments are expected to be free of entanglement. This work signifies an important step towards the realization of a continuous mild catalytic‐spinning (CATSPIN) process, where the polymer is directly synthesized into fiber shape at negligible chain branching and elegantly avoiding common limitations like thermal degradation or molecular entanglement. The covalently immobilized single‐atom Ni catalyst inside nano‐channels of the anodized Al2O3 membrane enables direct catalytic‐spinning of multifilament PE nanofibers near room temperature. Confinement in the nano‐pores has a positive influence on ethylene extrusion polymerization, namely on the chain‐growth and chain‐walking process–producing high‐performance microstructures and morphologies.