Unsymmetrical α,ω-Difunctionalized Long-Chain Compounds via Full Molecular Incorporation of Fatty Acids

Toughening of Bio-Based PA 6.19 by Copolymerization with PA 6.6 - Synthesis and Production of Melt-Spun Monofilaments and Knitted Fabrics

This work reports on the synthesis of statistical copolymers of bio-based PA 6.19 and PA 6.6 together with the production of melt-spun monofilaments for the production of sustainable textile fibers. The plant oil-based 1.19-nonadecanedioic acid is synthesized from bio-derived oleic acid via isomerizing methoxycarbonylation. The homopolymer PA 6.19 with a carbon-based bio-content of 72% shows a good elongation at break of 166%, but lower tensile strength than commercial PA 6 (43 MPa versus 82 MPa). Addition of adipic acid to form statistical PA 6.6/6.19 copolymers improves toughness while maintaining the high elongation at break. Two PA 6.6/6.19 copolymers with a carbon-based bio-content of 26% and 33% are successfully synthesized and exhibited comparable toughness (94  ±  6 MPa and 92  ±  2 MPa) to the commercial PA 6 (92  ±  15 MPa). The bio-based copolymers also exhibit a much lower water uptake than PA 6 and PA 6.6, resulting in a higher dimensional stability. Melt spinning of the oleic acid-based polyamides is successfully carried out to produce monofilaments with sufficient properties for further processing in a knitting process, demonstrating the capabilities of the bio-based PA 6.6/6.19 copolymers for use in the textile industry.

Assisted Tandem Pd Catalysis Enables Regiodivergent Heck Arylation of Transiently Generated Substituted Enol Ethers

Two complementary regiodivergent Pd-catalyzed assisted tandem [isomerization/Heck arylation] reactions are reported. They provide access to a broad array of acyclic trisubstituted vinyl ethers starting from readily available alkenyl ethers. In both cases, the isomerization is conducted with a [Pd-H] precatalyst supported by tris-tert-butyl phosphine ligands. When the catalyst is modified by the addition of a chelating bisphosphine ligand (dppp), an organic base (Cy₂NMe), sodium acetate, and aryl triflates are used as electrophiles, the α-arylation pathway is promoted preferentially. The β-arylation pathway is favored for electron-deficient and electron-neutral aryl halides when the catalyst is simply modified by the addition of an excess of an organic base (Et₃N) after completion of the isomerization reaction. Electron-rich aryl halides lead to reduced levels of regiocontrol. The moderate stereoselectivity obtained are proposed to reflect the absence of stereocontrol in the isomerization step. Computational analyses suggest that migratory insertion is selectivity-determining for both the arylations. For the β-selective arylation, an energy decomposition analysis underscored that electronic factors favor α-regioselectivity and steric effects favor β-regioselectivity. Preliminary investigations show that high levels of stereoselectivity can be achieved for the α-selective arylation by ligand control. Complementarily, reaction conditions for postcatalytic stereo-correction have also been identified for each catalytic system.

Bio-based monomers for amide-containing sustainable polymers

The field of sustainable polymers from renewable feedstocks is a fast-reviving field after the decades-long domination of petroleum-based polymers. Amide-containing polymers exhibit a wide range of properties depending on the type of amide (primary, secondary, and tertiary), amide density, and other molecular structural parameters (co-existing groups, molecular weight, and topology). Engineering amide groups into sustainable polymers via the "monomer approach" is an industrially proven strategy, while bio-based monomers are of enormous importance to bridge the gap between renewable sources and amide-containing sustainable polymers (AmSPs). This feature article aims at conceptualizing the monomer-design philosophy behind most of the reported AmSPs and is organized by discussing di-functional monomers for step-growth polymerization, cyclic monomers for ring-opening polymerization and amide-containing monomers for chain-growth polymerization. We also give a perspective on AmSPs with respect to monomer design and performance enhancement.

Identification of a Novel Oleic Acid Analog with Protective Effects in Multiple Cellular Models of Friedreich Ataxia

Friedreich ataxia (FRDA) is an inherited neurodegenerative disorder for which there is no cure or approved treatment. It is characterized by the loss or impaired activity of frataxin protein, which is involved in the biogenesis of iron-sulfur clusters. Our previous studies suggested that cell death in FRDA may involve ferroptosis, an iron-dependent form of cell death requiring lipid peroxidation. Based on reports that oleic acid acts as a ferroptosis inhibitor, we evaluated whether it, other fatty acids, and fatty acid derivatives could rescue viability in cellular models of FRDA. We identified a trifluoromethyl alcohol analog of oleic acid that was significantly more potent than oleic acid itself. Further evaluation indicated that the effects were stereoselective, although a specific molecular target has not yet been identified. This work provides a potential starting point for therapeutics to treat FRDA, as well as a valuable probe molecule to interrogate FRDA pathophysiology.

Polyethylene-like materials from plant oils

Polyethylene (PE) is the most important synthetic polymer material produced. Its excellent material properties arise from crystalline interactions in its hydrocarbon chains. This simple concept inspires studies of materials based on alternative non-fossil feedstocks and with additional traits such as a non-persistent nature. Renewable seed oil or microalgae oil lipids can serve as a feedstock for long-chain difunctional monomers. Catalytic conversion of their unsaturated fatty acids by e.g. isomerizing carbonylation or olefin metathesis yields long-chain monomers X-(CH₂)_n-X with 18-26 carbon atoms and terminal dicarboxy, diol or diamine groups (X), and ultralong-chain PE telechelics with 48 carbon atoms. These can be polymerized to polyesters, polycarbonates and other (ultra)long-chain polycondensates. These in many cases possess PE-like solid-state structure and properties. Unlike PE, they contain in-chain functional groups that can potentially enhance degradability. The crystalline and hydrophobic nature of the polymers decelerates degradation strongly compared to rapidly degrading shorter chain analogues. Our preliminary findings suggest that a non-persistent nature can be achieved for these materials. This review article is based on a lecture held at the Royal Society Discussion Meeting on Science to enable the circular economy. This article is part of a discussion meeting issue 'Science to enable the circular economy'.