| 1. |
- Abdelaziz, Omar Y., et al.
(författare)
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Recent strides toward transforming lignin into plastics and aqueous electrolytes for flow batteries
- 2024
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Ingår i: iScience. - : Elsevier Inc.. - 2589-0042. ; 27:4
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Forskningsöversikt (refereegranskat)abstract
- Lignin is an abundant polyaromatic polymer with a wide range of potential future uses. However, the conversion of lignin into valuable products comes at a cost, and medium- to high-value applications are thus appropriate. Two examples of these are polymers (e.g., as fibers, plasticizers, or additives) and flow batteries (e.g., as redox species). Both of these areas would benefit from lignin-derived molecules with potentially low molecular weight and high (electro)chemical functionality. A promising route to obtain these molecules is oxidative lignin depolymerization, as it enables the formation of targeted compounds with multiple functionalities. An application with high potential in the production of plastics is the synthesis of new sustainable polymers. Employing organic molecules, such as quinones and heterocycles, would constitute an important step toward the sustainability of aqueous flow batteries, and lignin and its derivatives are emerging as redox species, mainly due to their low cost and renewability.
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| 2. |
- Valsange, Nitin G., et al.
(författare)
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Semi-Crystalline and Amorphous Polyesters Derived from Biobased Tri-Aromatic Dicarboxylates and Containing Cleavable Acylhydrazone Units for Short-Loop Chemical Recycling
- 2024
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Ingår i: Macromolecules. - 0024-9297. ; 57:6, s. 2868-2878
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Tidskriftsartikel (refereegranskat)abstract
- Recycling polymers by site-specific scission into short-chain oligomers/polymers, followed by recoupling these to form the original polymer presents an energetically more favorable shorter-loop chemical recycling in comparison to recycling into monomers. Here, we present the synthesis and polymerization of triaromatic diesters to prepare polyesters with acylhydrazone units as weak structural links. Two diester monomers were prepared by combining methyl 5-chloromethyl-2-furoate, obtained from 5-chloromethylfurfural (CMF), with potentially biobased hydroquinone and resorcinol, respectively. The two diesters having a central phenyl ring flanked by two furan rings were polymerized with 1,6-hexanediol and 1,4-butanediol, respectively, together with controlled amounts of monofunctional ethyl levulinate to form telechelic ketone-terminated polyesters. Subsequent reactions of these telechelic polyesters with adipic dihydrazide yielded corresponding chain-extended polyesters with increased molecular weights ([η] = 0.29−0.52 dL g−1) with acylhydrazone units in the backbone. Thermogravimetric analysis showed a high thermal stability of the polyesters with thermal decomposition only above 275 °C. The polyesters containing the linear hydroquinone units were found to be semicrystalline materials with melting points at 158 and 192 °C, respectively, while those containing the kinked resorcinol units were fully amorphous with glass transition temperatures at 35 and 44 °C, respectively. Initial investigations of the chemical recyclability of the polyesters demonstrated that acylhydrazone units could be selectively cleaved to recover the original telechelic ketone-terminated polyesters, which could again be chain-extended to obtain a recycled polymer with molecular weights and properties very similar to those of the original polymer.
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| 3. |
- Valsange, Nitin, et al.
(författare)
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Improved chemical recyclability of 2,5-furandicarboxylate polyesters enabled by acid-sensitive spirocyclic ketal units
- 2024
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Ingår i: Green Chemistry. - 1463-9270. ; 26:5, s. 2858-2873
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Tidskriftsartikel (refereegranskat)abstract
- Incorporating hydrolytically sensitive functional groups into polymer backbones provides a feasible strategy to trigger their degradation to the starting monomers, thus enabling chemical recycling of the material. Here, we present two series of copolyesters in which a biobased spirocyclic ketal-functional diester monomer was incorporated into poly(butylene 2,5-furandicarboxylate) (PBLF) and poly(hexamethylene 2,5-furandicarboxylate) (PHLF), respectively. A two-step melt polycondensation resulted in copolyesters with moderate to high molecular weights, as confirmed by intrinsic viscosity values between 0.5-1.04 dL g-1. Thermogravimetric analysis showed a thermal stability up to 275 °C, and increasing char yields upon incorporation of the spirocyclic monomer. The crystallinity and melting points of the copolyesters decreased with the increasing content of the spirocyclic ketal units in the backbone. Copolyesters containing up to 15% of the spiro-ketal units were semicrystalline, while those containing 20 and 50% spiro-ketal units were completely amorphous. The hydrolytic degradation of copolyesters from the PHLF series was investigated using 3-12 M aq. HCl, and were found to degrade faster than the corresponding homopolyesters. Acid-catalyzed cleavage of the randomly distributed spiro ketal units promoted the rapid fragmentation of the polymer chain into small oligomers, which were subsequently hydrolyzed to the original chemical building blocks. The ketone-terminated telechelic oligomers obtained after the degradation of spirocyclic ketal units were also investigated in the direct polymerization with pentaerythritol. The initial results implied that the oligomers can be re-polymerized into the original polymer. Hence, this work demonstrated a feasible pathway towards chemically recyclable 2,5-furandicarboxylate polyesters with a tuneable degree of crystallinity
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