Kyoko Nozaki

Polyethylene (PE) functionalization is a promising route to expand material performance while preserving the favorable properties of PE, such as mechanical robustness. However, the influence of isolated in-chain functional groups embedded in the PE backbone on the crystallization of PE remains poorly understood. Herein, we investigate the crystallization behavior of polyethylene bearing in-chain carbonyl (PE-CO) and amide (PE-CONH) groups that are embedded randomly in the PE backbone in a highly isolated manner. PE-CONH was obtained from PE-CO via main-chain editing, ensuring closely matched in-chain group distributions. Strikingly, PE-CO and PE-CONH showed a distinct two-step evolution of crystallinity during cooling at a constant rate. Such a two-step crystallization phenomenon was found in random copolymers for the first time. A comprehensive multiscale analysis revealed the molecular mechanism of the two-step crystallization: the in-chain groups were rejected from the PE crystalline phase in the first step but were later incorporated into the crystal lattice in the second step. Amide groups induced a more pronounced delay in the onset of the second step than carbonyl groups did. The discovery of the two-step crystallization offers a new opportunity for designing advanced PE-derived materials through precise main-chain modification.

The hydrogenolysis of lignin‐derived aromatic oxygenates into aromatic hydrocarbons under mild conditions remains a significant challenge due to competing over‐hydrogenation of the aromatic ring. Here, we report a highly active and water‐tolerant Pt/WO ₃ –ZrO ₂ catalyst that enables the conversion of a broad range of aromatic oxygenates into aromatic hydrocarbons in a water/decane biphasic system at 90 °C under ambient pressure with a H ₂ partial pressure of only 0.1 atm. The biphasic environment efficiently suppresses side reactions by continuously extracting the arene products into the organic phase, thereby minimizing further hydrogenation of the aromatic ring. Kinetic analysis shows that C(sp ² )—OMe cleavage precedes C(sp ² )—OH cleavage in the hydrogenolysis of 4‐ethylguaiacol, while mechanistic studies reveal that the strong Brønsted acidity and redox properties of the WO ₃ –ZrO ₂ support enable hydrogenolysis under exceptionally mild conditions. The catalyst exhibits broad substrate scope, high selectivity for aromatic products, and good reusability, providing an efficient platform for producing aromatic hydrocarbons from lignin‐derived oxygenates.

Understanding the active structure of phosphate‐based supports is essential for designing catalysts for selective C─O bond hydrogenolysis. Herein, ³¹ P solid‐state NMR analysis revealed that the support in our previously reported Pt/Al(PO ₃ ) ₃ catalyst was actually an aluminum condensed phosphate mixture (ACPM), rather than a single aluminum metaphosphate (AMP) phase, consisting of aluminum metaphosphate (AMP), aluminum cyclohexaphosphate (ACP), and aluminum tripolyphosphate (ATPP), with the ATPP phase located on the catalyst surface. Guided by these findings, a Pt/ATPP catalyst was developed, showing high selectivity for the hydrogenolysis of 4‐heptylphenol to heptylbenzene. Mechanistic studies suggested that the Lewis acid sites on ATPP contribute to the enhanced selectivity by facilitating C─O bond activation, a key step in phenol hydrogenolysis.

Understanding the active structure of phosphate‐based supports is essential for designing catalysts for selective C─O bond hydrogenolysis. Herein, ³¹ P solid‐state NMR analysis revealed that the support in our previously reported Pt/Al(PO ₃ ) ₃ catalyst was actually an aluminum condensed phosphate mixture (ACPM), rather than a single aluminum metaphosphate (AMP) phase, consisting of aluminum metaphosphate (AMP), aluminum cyclohexaphosphate (ACP), and aluminum tripolyphosphate (ATPP), with the ATPP phase located on the catalyst surface. Guided by these findings, a Pt/ATPP catalyst was developed, showing high selectivity for the hydrogenolysis of 4‐heptylphenol to heptylbenzene. Mechanistic studies suggested that the Lewis acid sites on ATPP contribute to the enhanced selectivity by facilitating C─O bond activation, a key step in phenol hydrogenolysis.

We disclose a new route for the preparation of linear polyethylene (PE)–poly(methyl acrylate) (PMA) diblock copolymers. The PE segment is synthesized by coordination–insertion polymerization (CIP), and the PMA segment is polymerized through radical polymerization (RP). Notably, no solvent is used during the process. Linear alkyl–nickel species synthesized by the CIP of ethylene under a solid−gas two-phase reaction are thermally activated at room temperature in neat methyl acrylate (MA), which triggers RP. Diblock copolymer formation and its composition are supported by a unimodal SEC shift and ¹ H/ ¹³ C NMR analyses. The presence of small PE crystals in amorphous PMA is implied by powder XRD analysis. The difference in the reactivities of MA and methyl methacrylate (MMA) suggests that RP initiates through the thermal homolytic scission of the C−Ni bond of α-carbonyl Ni species.

The recent achievement of a nonalternating ethylene/carbon monoxide (CO) copolymerization was a long-sought breakthrough. Their in-chain keto functional groups endow the resulting polyethylenes (keto-PEs) with photodegradability. To date, only two types of catalysts, based on long-known structural motifs, are capable of this challenging copolymerization to keto-PE materials, raising the question whether the reaction is restricted to this narrow scope. Here, we report a diverse range of neutral Ni(II) complexes provides access to keto-PEs, including a phosphine imidate Ni(II) catalyst that is competitive with state-of-the-art catalysts and a N-heterocyclic-carbene (NHC) phenolate Ni(II) catalyst with exceptional preference for ethylene vs CO incorporation. Density functional theory (DFT) calculations rationalize the observed selectivity for nonalternating and alternating chain growth from the individual catalysts' activation barrier differences ΔΔG^‡ and identify the strong trans-effect of the [NHC,O]-ligand and its high steric hindrance as origins of the desirable exceptionally low preference for CO incorporation.

Nitrile-containing polymers feature extensively in consumer products and industry, yet efficient catalytic upcycling strategies remain underexplored. Herein, we report a general catalytic degradation strategy that enables the transformation of diverse nitrile-containing polymers via a tandem process combining nickel-catalyzed decyanation with ruthenium-catalyzed ethenolysis. This strategy enables cyano group removal and recycling into value-added nitrile compounds without releasing highly toxic cyanide species. Moreover, the process can be performed in a one-pot manner by employing ethylene as both the cyano group acceptor and the metathesis partner, thereby streamlining the degradation process, enhancing overall efficiency, and increasing potential for industrial adoption.