C–H Functionalization of Polyolefins to Access Reprocessable Polyolefin Thermosets

Journal of the American Chemical Society, Journal Year: 2023, Volume and Issue: 145(50), P. 27450 - 27458

Published: Dec. 11, 2023

Upcycling plastic waste into reprocessable materials with performance-advantaged properties would contribute to the development of a circular plastics economy. Here, we modify branched polyolefins and postconsumer polyethylene through versatile C–H functionalization approach using thiosulfonates as privileged radical group transfer functionality. Cross-linking functionalized polytopic amines provided dynamically cross-linked polyolefin networks enabled by associative bond exchange diketoenamine A combination resonant soft X-ray scattering grazing incidence revealed hierarchical phase morphology in which diketoenamine-rich microdomains phase-separate within amorphous regions between crystallites. The dynamic covalent cross-links microphase separation results useful improved mechanical properties, including ∼4.5-fold increase toughness, reduction creep deformation at temperatures relevant use, high-temperature structural stability compared parent polyolefin. nature provides stress relaxation elevated temperatures, iterative reprocessing polymer network little cycle-to-cycle property fade. ability convert thermoformable material attractive thermomechanical additional optionality for upcycling enable future circularity.

Language: Английский

---

Chemical Modification of Oxidized Polyethylene Enables Access to Functional Polyethylenes with Greater Reuse

Journal of the American Chemical Society, Journal Year: 2023, Volume and Issue: 145(39), P. 21527 - 21537

Published: Sept. 21, 2023

Polyethylene is a commodity material that widely used because of its low cost and valuable properties. However, the lack functional groups in polyethylene limits use applications include adhesives, gas barriers, plastic blends. The inertness makes it difficult to install would enhance properties enable programmed chemical decomposition. To overcome these deficiencies, installation pendent imbue with enhanced an attractive strategy inherent limitations. Here, we describe strategies derivatize oxidized contains both ketones alcohols monofunctional variants bulk superior those unmodified polyethylene. Iridium-catalyzed transfer dehydrogenation acetone furnished polyethylenes only ketones, ruthenium-catalyzed hydrogenation hydrogen alcohols. We demonstrate ratio can be controlled by reduction stoichiometric hydride-containing reagents. serve as sites introduce esters oximes onto polymer, thereby improving surface over These were removed hydrolysis regenerate original oxygenated polyethylenes, showing how functionalization lead materials circularity. Waste equally amenable oxidative derivatization material, this low- or negative-value feedstock prepare higher value. Finally, derivatized polymers distinct solubilities separated from mechanically mixed blends selective dissolution, demonstrating novel approaches for distinguishing separating mixture.

Language: Английский

---

A General Photocatalytic Strategy for Nucleophilic Amination of Primary and Secondary Benzylic C–H Bonds

Journal of the American Chemical Society, Journal Year: 2023, Volume and Issue: 145(33), P. 18487 - 18496

Published: Aug. 11, 2023

We report a visible-light photoredox-catalyzed method that enables nucleophilic amination of primary and secondary benzylic C(sp3)-H bonds. A novel amidyl radical precursor organic photocatalyst operate in tandem to transform bonds into carbocations via sequential hydrogen atom transfer (HAT) oxidative radical-polar crossover. The resulting carbocation can be intercepted by variety N-centered nucleophiles, including nitriles (Ritter reaction), amides, carbamates, sulfonamides, azoles, for the construction pharmaceutically relevant C(sp3)-N under unified reaction conditions. Mechanistic studies indicate HAT is radical-mediated operates reductive quenching pathway. These findings establish mild, metal-free, modular protocol rapid diversification library aminated products.

Language: Английский

---

Diverse functional polyethylenes by catalytic amination

Science, Journal Year: 2023, Volume and Issue: 381(6665), P. 1433 - 1440

Published: Sept. 28, 2023

Functional polyethylenes possess valuable bulk and surface properties, but the limits of current synthetic methods narrow range accessible materials prevent many envisioned applications. Instead, these are often used in composite films that challenging to recycle. We report a Cu-catalyzed amination form mono- bifunctional containing series polar groups substituents. Designed catalysts with hydrophobic moieties enable linear branched without chain scission or cross-linking, leading otherwise inaccessible combinations functional architectures. The resulting tunable including toughness, adhesion metal, paintability, water solubility, which could unlock applications for reduce need complex composites.

Language: Английский

---

Catalytic Amounts of an Antibacterial Monomer Enable the Upcycling of Poly(Ethylene Terephthalate) Waste

Advanced Materials, Journal Year: 2023, Volume and Issue: 35(20)

Published: Feb. 21, 2023

Poly(ethylene terephthalate) (PET) is an important polymer with annual output second only to polyethylene. The development of PET recycling technologies therefore necessary not eliminate the harm associated white pollution and microplastics, but also reduce carbon emissions. Antibacterial PET, one most high-value advanced materials, has improved ability treat bacterial infections. However, current methods manufacturing commercial antibacterial require blending excess metal-based agents, which leads biotoxicity a nonpersistent activity. In addition, high-efficiency organic agents have yet be employed in due their poor thermal stabilities. Herein, solid-state reaction for upcycling waste using novel hyperthermostable monomer described. This catalyzed by residual catalyst present waste. It found that catalytic amount enabled low-cost produce recycled strong persistent activity, as well similar properties virgin PET. work provides feasible economic strategy large-scale exhibits potential application industry.

Language: Английский

---