Synthesis of low-entangled UHMWiPP using Hf-pyridyl amido catalyst activated by trityl tetrakis (pentafluorophenyl) borate

Abstract

Recently we demonstrated that low entangled ultra-high molecular weight isotactic polypropylene having molecular weight up to 2.4 million g/mol can be synthesized using a Hf-pyridyl amido catalyst activated by dimethylanilinium tetrakis (pentafluorophenyl)borate. Herein, we used an aprotic borate (trityl tetrakis(pentafluorophenyl)borate) to activate a Hf-pyridyl amido catalyst leading to a fast and ease catalyst activation even at lower temperatures, thus yielding exceptionally high molecular weight (up to 7.7 million g/mol) having improved tacticity (mmmm up to 98.5 %) and peak melting temperature (up to 165 °C). Thus synthesized polymers show extremely slow equilibration process by rheological characterization, indicating the low entangled state. These polymers can be processed in solid-state, without melting, into uniaxial drawn tapes having high tensile strength (1.46 N/tex) and tensile modulus (33 N/tex). The superior mechanical properties enable the tapes to be used as reinforcing material for commercial polypropylene grades, opening the possibilities of making one-component easy-to-recycle composites.