| 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. |
- Aristizábal-Lanza, Lucía, et al.
(författare)
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Comparison of the enzymatic depolymerization of polyethylene terephthalate and AkestraTM using Humicola insolens cutinase
- 2022
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Ingår i: Frontiers in Chemical Engineering. - : Frontiers Media SA. - 2673-2718. ; 4
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Tidskriftsartikel (refereegranskat)abstract
- The enzymatic depolymerization of synthetic polyesters has become of great interest in recycling plastics. Most of the research in this area focuses on the depolymerization of polyethylene terephthalate (PET) due to its widespread use in various applications. However, the enzymatic activity on other commercial polyesters is less frequently investigated. Therefore, AkestraTM attracted our attention, which is a copolymer derived from PET with a partially biobased spirocyclic acetal structure. In this study, the activity of Humicola insolens cutinase (HiCut) on PET and AkestraTM films and powder was investigated. HiCut showed higher depolymerization activity on amorphous PET films than on Akestra™ films. However, an outstanding performance was achieved on AkestraTM powder, reaching 38% depolymerization in 235h, while only 12% for PET powder. These results are consistent with the dependence of the enzymes on the crystallinity of the polymer since Akestra™ is amorphous while the PET powder has 14% crystallinity. On the other hand, HiCut docking studies and molecular dynamic simulations (MD) suggested that the PET-derived mono (hydroxyethyl)terephthalate dimer (MHET)2 is a hydrolyzable ligand, producing terephthalic acid (TPA), while the Akestra™-derived TPA-spiroglycol ester is not, which is consistent with the depolymerization products determined experimentally. MD studies also suggest ligand-induced local conformational changes in the active site.
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| 3. |
- Din, Salah Ud, et al.
(författare)
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The Purification and Characterization of a Cutinase-like Enzyme with Activity on Polyethylene Terephthalate (PET) from a Newly Isolated Bacterium Stenotrophomonas maltophilia PRS8 at a Mesophilic Temperature
- 2023
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Ingår i: Applied Sciences (Switzerland). - : MDPI AG. - 2076-3417. ; 13:6
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Tidskriftsartikel (refereegranskat)abstract
- A polyethylene terephthalate (PET)-degrading bacterium identified as Stenotrophomonas maltophilia PRS8 was isolated from the soil of a landfill. The degradation of the PET bottle flakes and the PET prepared as a powder were assessed using live cells, an extracellular medium, or a purified cutinase-like enzyme. These treated polymers were analyzed using Fourier transform infrared spectroscopy (FTIR) and scanning electron microscopy (SEM). The depolymerization products, identified using HPLC and LC-MS, were terephthalic acid (TPA), mono(2-hydroxyethyl)-TPA (MHET), and bis(2-hydroxyethyl)-TPA (BHET). Several physicochemical factors were optimized for a better cutinase-like enzyme production by using unique single-factor and multi-factor statistical models (the Plackett–Burman design and the central composite design software). The enzyme was purified for homogeneity through column chromatography using Sephadex G-100 resin. The molecular weight of the enzyme was approximately 58 kDa. The specific activity on para nitrophenyl butyrate was estimated at 450.58 U/mg, with a purification of 6.39 times and a yield of 48.64%. The enzyme was stable at various temperatures (30–40 °C) and pH levels (8.0–10.0). The enzyme activity was significantly improved by the surfactants (Triton X-100 and Tween-40), organic solvent (formaldehyde), and metals (NiCl2 and Na2SO4). The extracellular medium containing the cutinase-type enzyme showed a depolymerization yield of the PET powder comparable to that of Idonella skaiensis IsPETase and significantly higher than that of Humicola insolens thermostable HiCut (HiC) cutinase. This study suggests that S. maltophilia PRS8 is able to degrade PET at a mesophilic temperature and could be further explored for the sustainable management of plastic waste.
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| 4. |
- Guo, Zengwei, et al.
(författare)
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Development of Circularly Recyclable Low Melting Temperature Bicomponent Fibers toward a Sustainable Nonwoven Application
- 2021
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Ingår i: ACS Sustainable Chemistry and Engineering. - : American Chemical Society. - 2168-0485. ; 9:49, s. 16778-16785
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Tidskriftsartikel (refereegranskat)abstract
- Sustainable low melting temperature bicomponent polyester fibers that can be circularly recycled were developed. The potentially biobased poly(hexamethylene terephthalate) (PHT), acting as the low melting temperature sheath material in the designed bicomponent fibers, was synthesized in a pilot scale. The obtained PHT with an intrinsic viscosity of 0.47 dL/g showed suitable processability when it was processed together with a poly(butylene terephthalate) (PBT) core in a melt-spinning process of bicomponent fibers. Compared with the commercial low melting temperature terephthalate-isophthalate copolyester LMP-160, PHT showed superior mechanical properties according to DMA analysis. The low melting temperature bicomponent fibers with a ratio of the PBT core and PHT sheath at 70:30 were produced smoothly at 290 °C in a pilot melt-spinning line. Preliminary chemical recycling investigations by methanolysis revealed that PHT/PBT bicomponent fibers were completely depolymerized within 2 h at 200 °C, yielding pure terephthalate, which could be conveniently separated and recycled. This indicated the feasibility of circular recycling, which will greatly improve the sustainability of nonwovens thermally bonded by these new bicomponent fibers. © 2021 The Authors.
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| 5. |
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| 6. |
- Mankar, Smita V., et al.
(författare)
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Short-Loop Chemical Recycling via Telechelic Polymers for Biobased Polyesters with Spiroacetal Units
- 2023
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Ingår i: ACS Sustainable Chemistry & Engineering. - : American Chemical Society (ACS). - 2168-0485. ; 11:13, s. 5135-5146
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Tidskriftsartikel (refereegranskat)abstract
- Spirocyclic acetal structures have recently received growing attention in polymer science due to their dual potential to raise the glass transition temperature (Tg) and enable chemical recycling of biobased polymers. In the present work, a vanillin-based diol with a spirocyclic acetal structure was incorporated in a series of rigid amorphous polyesters based on neopentyl glycol and dimethyl terephthalate (DMT). Up to 50 mol % of spirocyclic diol (with respect to DMT) could be incorporated in the copolyesters, but a reasonably high molecular weight was only achieved when ≤30 mol % of the spirocyclic diol was used. The presence of the spiroacetal units in the polyesters not only enhanced the Tg (up to 103 °C) and thermal stability (T5 ≥ 300 °C) but also the oxygen barrier of solution-cast films. We found that the acetal units in the copolyesters could be selectively hydrolyzed under acidic conditions while virtually retaining all of the ester bonds in the polymer backbone. After acidic hydrolysis, telechelic polymers exclusively terminated by two aldehyde end groups were obtained. In this work, we have demonstrated that these telechelic polyesters can be conveniently converted back into poly(acetal-ester)s via cycloacetalization reactions with pentaerythritol.
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| 7. |
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| 8. |
- 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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