Shi Jake X, Ciccia Nicodemo R, Pal Subhajit, Kim Diane D, Brunn John N, Lizandara-Pueyo Carlos, Ernst Martin, Haydl Alexander M, Messersmith Phillip B, Helms Brett A, Hartwig John F
Department of Chemistry, University of California, Berkeley, California 94720, United States.
Division of Chemical Sciences, Lawrence Berkeley National Laboratory, Berkeley, California 94720, United States.
J Am Chem Soc. 2023 Oct 4;145(39):21527-21537. doi: 10.1021/jacs.3c07186. Epub 2023 Sep 21.
Polyethylene is a commodity material that is widely used because of its low cost and valuable properties. However, the lack of functional groups in polyethylene limits its use in applications that include adhesives, gas barriers, and plastic blends. The inertness of polyethylene makes it difficult to install groups that would enhance its properties and enable programmed chemical decomposition. To overcome these deficiencies, the installation of pendent functional groups that imbue polyethylene with enhanced properties is an attractive strategy to overcome its inherent limitations. Here, we describe strategies to derivatize oxidized polyethylene that contains both ketones and alcohols to monofunctional variants with bulk properties superior to those of unmodified polyethylene. Iridium-catalyzed transfer dehydrogenation with acetone furnished polyethylenes with only ketones, and ruthenium-catalyzed hydrogenation with hydrogen furnished polyethylenes with only alcohols. We demonstrate that the ratio of these functional groups can be controlled by reduction with stoichiometric hydride-containing reagents. The ketones and alcohols serve as sites to introduce esters and oximes onto the polymer, thereby improving surface and bulk properties over those of polyethylene. These esters and oximes were removed by hydrolysis to regenerate the original oxygenated polyethylenes, showing how functionalization can lead to materials with circularity. Waste polyethylenes were equally amenable to oxidative functionalization and derivatization of the oxidized material, showing that this low- or negative-value feedstock can be used to prepare materials of higher value. Finally, the derivatized polymers with distinct solubilities were separated from mechanically mixed plastic blends by selective dissolution, demonstrating that functionalization can lead to novel approaches for distinguishing and separating polymers from a mixture.
聚乙烯是一种商品材料，因其成本低且具有宝贵的性能而被广泛使用。然而，聚乙烯中缺乏官能团限制了其在包括粘合剂、气体阻隔材料和塑料共混物等应用中的使用。聚乙烯的惰性使得难以引入能够增强其性能并实现可控化学分解的基团。为了克服这些不足，引入侧链官能团以使聚乙烯具有增强性能是一种克服其固有局限性的有吸引力的策略。在这里，我们描述了将含有酮和醇的氧化聚乙烯衍生化为具有优于未改性聚乙烯本体性能的单官能变体的策略。铱催化的与丙酮的转移脱氢反应得到仅含酮的聚乙烯，钌催化的与氢气的氢化反应得到仅含醇的聚乙烯。我们证明这些官能团的比例可以通过用化学计量的含氢化物试剂还原来控制。酮和醇作为在聚合物上引入酯和肟的位点，从而比聚乙烯改善了表面和本体性能。这些酯和肟通过水解被去除以再生原始的氧化聚乙烯，展示了功能化如何导致具有循环性的材料。废弃聚乙烯同样适合进行氧化功能化和氧化材料的衍生化，表明这种低值或负价值的原料可用于制备更高价值的材料。最后，通过选择性溶解从机械混合的塑料共混物中分离出具有不同溶解度的衍生化聚合物，证明功能化可以导致从混合物中区分和分离聚合物的新方法。
