Post-functionalization of narrowly dispersed PE waxes generated using tuned N,N,N'-cobalt ethylene polymerization catalysts substituted with ortho-cycloalkyl groups

https://doi.org/10.1016/j.polymer.2020.123294

 

Abstract

Six structurally related bis(arylimino)trihydroquinolyl-cobalt (II) chloride complexes [2-(ArNCCH₃)-8-(ArN)-5,6,7-C₉H₈N]CoCl₂ (Ar = 2-(C₅H₉)-6-MeC₆H₃ Co1, 2-(C₆H₁₁)-6-MeC₆H₃ Co2, 2-(C₈H₁₅)-6-MeC₆H₃ Co3, 2-(C₅H₉)-4,6-Me₂C₆H₂ Co4, 2-(C₆H₁₁)-4,6-Me₂C₆H₂ Co5, 2-(C₈H₁₅)-4,6-Me₂C₆H₂ Co6), distinguishable by the ring size of the ortho-cycloalkyl substituent and type of para-R group, have been synthesized and characterized. A distorted square pyramidal geometry is a feature of the molecular structure of Co4 with the two ortho-cyclopentyl groups located on neighboring N-aryl groups trans-configured. Compounds Co1 – Co6, on activation with methylaluminoxane (MAO) or modified MAO (MMAO), proved highly productive catalysts for ethylene polymerization at 60 °C [up to 17.1 × 10⁶ g (PE) mol⁻¹(Co) h⁻¹ for cyclopentyl-containing Co4/MAO]; even at 90 °C significant activity was attainable (up to 6.75 × 10⁶ g (PE) mol⁻¹(Co) h⁻¹). Strictly linear polyethylene waxes of low molecular weight (ca. 1.50 kg mol⁻¹), narrow dispersity (M_w/M_n range: 1.1–2.4) and incorporating high levels of vinyl end-groups were generated. Post-functionalization of these PE waxes by epoxidation, thiol-ene addition and cross-olefin metathesis to form e-PE, PE-S-CH₂CH₂NH₂·HCl and PE-MMA, respectively, has been demonstrated. For comparative purposes, [2-(ArNCCH₃)-8-ArN-5,6,7-C₉H₈N]CoCl₂ (Ar = 2,4,6-Me₃C₆H₂ Co_o-Me, 2-(Ph₂CH)-4,6-Me₂C₆H₂ Co_o-CHPh2) have also been prepared and evaluated as polymerization catalysts.

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