Carbonyl functionalized polyethylene materials via Ni- and Pd-diphosphazane monoxide catalyzed nonalternating copolymerization

Synthesis and Deconstruction of Polyethylene-type Materials

“…Nonalternating ethylene-CO copolymerizations have also been demonstrated more recently with cationic Pd­(II) catalysts but at still relatively high keto incorporations that also reflect in significantly higher melting points compared to polyethylene. , Further development and studies of these catalysts, as well as their Ni­(II) analogues, yielded keto-PEs with low CO incorporation and high molecular weights ( M n up to 10 5 g mol –1 ) …”

“…69,70 Further development and studies of these catalysts, as well as their Ni(II) analogues, yielded keto-PEs with low CO incorporation and high molecular weights (M n up to 10 5 g mol −1 ). 71 From a mechanistic point of view the ability of the aforementioned neutral catalysts to generate keto-PE arises from the barrier of the nonalternating pathway of chain growth being competitive to that of alternating chain growth (Figure 8). 45,46,62 DFT studies starting from a five-membered chelate formed by CO insertion revealed that Ni-phosphinophenolate catalysts indeed have a ΔΔG ‡ alt-nonalt similar to Pd-phosphinosulfonate complexes despite differing in the nature of the ratedetermining steps for both pathways.…”

Keto-Polyethylenes with Controlled Crystallinity and Materials Properties from Catalytic Ethylene–CO–Norbornene Terpolymerization

“…Such polar functional groups in the hydrocarbon-based polyethylene chain increase its polarity and therefore enhance barrier properties, adhesion to or compatibility with polar materials. − This is commonly achieved by either postpolymerization C–H oxidation , or by copolymerization of ethylene with polar vinyl monomers. − In contrast to vinyl comonomers, the copolymerization of ethylene with carbon monoxide (CO) can yield keto groups directly in the polyethylene backbone. At low functional group densities, these in-chain keto groups can be included into the polyethylene crystallites. − Additionally, these in-chain keto groups impart photodegradability to the polymer, which offers a potential alleviation of the environmental impacts of mismanaged PE waste. − In particular, linear HDPE-like materials from catalytic copolymerization of ethylene and CO have been long sought for and are particularly challenging to access due to preferred insertion of CO over the ethylene comonomer, often leading to the formation of alternating polyketone ( T m > 220 °C) instead. − Such materials have only recently been enabled by nonalternating copolymerization of ethylene and CO. ,− Advanced neutral phosphinophenolate Ni­(II) catalysts − have been particularly suitable for this direct catalytic copolymerization of ethylene and CO, yielding photodegradable keto-PE materials with high molecular weights (up to M w 400 000 g mol –1 ) and virtually uncompromised HDPE-like properties. ,,, …”

Mechanistic Insights into Cationic [P,O]-Pd-Catalyzed Chain-Transfer Copolymerization of Ethylene with Carbon Monoxide

“…We discovered a series of cationic diphosphazane monoxide-coordinated palladium/nickel complexes ([P,O]-Pd/Ni) based on the electronic and steric modulation strategy , for the highly efficient copolymerization of ethylene with CO, affording alternating polyketone, nonalternating polyketone, , and in-chain ketone polyethylene materials, and [P,O]-Ni exhibited a remarkable productivity of 31150 g PK/g Ni . However, nonprotonic solvents are generally required for this [P,O]-type catalyst, and the polymerization features low initiation efficiency and a lower tendency for chain transfer, thus yielding high-molecular-weight polyketones. − Concerning the specific role of methanol in the diphosphine–Pd catalyst system, we investigated the feasibility of chain transfers and the deactivation/reactivation pathways toward [P,O]-Pd/Ni-catalyzed copolymerization in methanol using the state-of-the-art electrospray ionization mass spectrometry (ESI-MS) (Figure ). The presence of chain transfer regulated the molecular weight values of the resulting polyketones within the range of 8.13–238 kg/mol, and more than two times higher productivity was obtained with 1,4-benzoquinone (BQ) additives.…”

“…We discovered a series of cationic diphosphazane monoxidecoordinated palladium/nickel complexes ( on the electronic and steric modulation strategy 39,40 for the highly efficient copolymerization of ethylene with CO, affording alternating polyketone, nonalternating polyketone, 41,42 and in-chain ketone polyethylene materials, 43 and [P,O]-Ni exhibited a remarkable productivity of 31150 g PK/g Ni. 44 However, nonprotonic solvents are generally required for this [P,O]-type catalyst, 45 and the polymerization features low initiation efficiency and a lower tendency for chain transfer, 46 thus yielding high-molecular-weight polyketones.…”