A co-anchoring strategy for the synthesis of polar bimodal polyethylene

Abstract

Since polar groups can poison the metal centers in catalysts, the incorporation of polar comonomers usually comes at the expense of catalytic activity and polymer molecular weight. In this contribution, we demonstrate polar bimodal polyethylene as a potential solution to this trade-off. The more-polar/more-branched low-molecular-weight fraction provides polarity and processability, while the less-polar/less-branched high-molecular-weight fraction provides mechanical and melt properties. To achieve high miscibility between these two fractions, three synthetic routes are investigated: mixtures of homogeneous catalysts, separately supported heterogeneous catalysts, and a co-anchoring strategy (CAS) to heterogenize different homogeneous catalysts on one solid support. The CAS route is the only viable strategy for the synthesis of polar bimodal polyethylene with good molecular level entanglement and minimal phase separation. This produces polyolefin materials with excellent mechanical properties, surface/dyeing properties, gas barrier properties, as well as extrudability and 3D-printability.

Heterogenization Strategies for Nickel Catalyzed Synthesis of Polyolefins and Composites

“…However, there are very few studies on the in-reactor blends of polar-functionalized polyolefins and their composites. Recently, we developed a coanchoring strategy by supporting two or more homogeneous transition metal catalysts with different copolymerization performance (Ni4@support and Ni8@support: high molecular weight and low polar monomer incorporation; Ni9@support: low molecular weight and high polar monomer incorporation) to prepare functionalized bimodal polyethylene in-reactor blends (Figure A) . The polar bimodal polyethylene in-reactor blends prepared by copolymerization of ethylene and polar monomer ( tert -butyl acrylate/methyl undecylenate) catalyzed by coanchored heterogeneous catalysts led to tunable molecular weight of 17.4–244.8 × 10 4 g mol –1 ( M n ), PDI of 3.7–92.3, and polar monomer incorporation of 0.2–1.4 mol %.…”

“…PPE-Ni8-MgO and PPE-Ni9-MgO (unimodal), PPE-Ni8/Ni9-MgO (bimodal polar polyethylene from coanchoring), and PPE-Ni8-MgO/Ni9-MgO (bimodal polar polyethylene from mixed supported catalysts). Reproduced with permission from ref . Copyright 2023 Nature Springer.…”

“…(C) Water contact angles of ethylene/ tert -butyl acrylate copolymers (red, unimodal polar polyethylene, blue, polar bimodal polyethylene by the coanchoring strategy). Reproduced with permission from ref . Copyright 2023 Nature Springer.…”

“…(D) Oxygen permeability coefficient of polyethylene samples at 25 °C (black, unimodal polar polyethylene, red, polar bimodal polyethylene by the coanchoring strategy, blue, polar polyethylene mixed heterogeneous catalysts). Reproduced with permission from ref . Copyright 2023 Nature Springer.…”

“…(E) 3D-printed samples of polar bimodal polyethylene by the coanchoring strategy. Reproduced with permission from ref . Copyright 2023 Nature Springer.…”