Name: designed for molecular recycling: a lignin-derived semi-aromatic biobased polymer
Uploaded: 2020-11-30T14:00:00
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Les auteurs sont reconnaissants du soutien financier de l’Organisation néerlandaise pour la recherche scientifique (NWO) (subvention 023.007.020 accordée à Jack van Schijndel).

1. Condensation verte du knoevenagel du syringaldéhyde vers l’acide sinapinique avec 5 mol% de bicarbonate d’ammonium
<ol><li>Ajouter l’acide malonique (20,81 g, 200,0 mmol) avec le syringaldéhyde (36,4 g, 200,0 mmol) dans une fiole à fond rond de 250 mL. Dissoudre les deux constituants dans 20,0 mL d’acétate d’éthyle et ajouter le bicarbonate d’ammonium (790 mg, 10,0 mmol) à la fiole. REMARQUE: Pour assurer l’achèvement complet de la réaction de condensation, l’évaporateur rotatif peut êtr...

<ol>
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A., Meuldijk, J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Mechanistic+considerations+and+characterization+of+ammonia-based+catalytic+active+intermediates+of+the+Green+Knoevenagel+reaction+of+various+benzaldehydes.">Mechanistic considerations and characterization of ammonia-based catalytic active intermediates of the Green Knoevenagel reaction of various benzaldehydes.</a> Green Chemistry Letters and Reviews. 12 (3), 323-331 (2019).</li><li>Sheldon, R. A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Fundamentals+of+green+chemistry:+efficiency+in+reaction+design.">Fundamentals of green chemistry: efficiency in reaction design.</a> Chemical Society Reviews. 41 (4), 1437-1451 (2012).</li><li>van Schijndel, J., Molendijk, D., Canalle, L. A., Rump, E. 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Lorsque l’acide dihydrosinapinique était chauffé dans un récipient de réaction, la sublimation du matériau de départ se produisait, et cet effet était renforcé lorsqu’un vide était appliqué. L’acétylation a été réalisée sur l’acide dihydrosinapinique pour éviter la sublimation. Kricheldorf et al.12,27 ont reconnu que non seulement l’acétylation, mais aussi la di- et l’oligomérisation se produisaient. Cependant, ces monomères et olig...

Contrairement à l’incinération des déchets polymères, le recyclage chimique offre la possibilité de récupérer les monomères. Le recyclage chimique est un choix logique à la fin de la vie technique des matériaux polymères puisque ces matériaux polymères sont produits chimiquement1. Il existe deux façons de recycler chimiquement le matériau polymère, la pyrolyse et le recyclage moléculaire2. Avec la pyrolyse, le matériau polymère est transformé en produits de plus grande valeur en utilisant des conditionsextrêmes3,4. Le recyclage moléculaire est une méthode efficace de récupération des matières premières par dépolymérisation. Après dépolymérisation, les unités monomères peuvent être repolymérisées en matériaux polymères vierges5. La disponibilité de monomères appropriés pour appliquer le recyclage moléculaire à plus grande échelle est une source de besoin. Le problème actuel du plastique dicte que la société exige des matériaux polymères robustes et robustes. Dans le même temps, il est également préférable que les mêmes matériaux polymères soient facilement recyclables et ne perdurent pas dans l’environnement. Les matériaux polymères actuels ayant de bonnes propriétés thermiques et mécaniques ne se dépolymérisent pas facilement6.
La lignine, que l’on trouve couramment dans les plantes vasculaires, est responsable de 30% de la teneur naturelle en carbone dans le monde et est le deuxième biopolymère le plus abondant après la cellulose. La lignine a une structure amorphe complexe et semble être une alternative appropriée pour remplacer les aromatiques extraits de matériaux fossiles. La structure tridimensionnelle de la lignine offre résistance et rigidité au bois, ainsi qu’une résistance à la dégradation. Chimiquement parlant, la lignine est un thermodurcissable polyphénolique très complexe. Il se compose d’une composition variable de trois structures différentes de phénylpropane méthoxylé. Le syringyle, le giacyle et le p-hydroxyphényle (souvent abrégés en S, G et H, respectivement) sont dérivés des monolignols alcool sinapylique, alcool coniférylique et alcool p-coumarylique7. La distribution de ces unités diffère selon le type de biomasse, avec le bois résineux, par exemple, composé principalement d’unités de guaiacyle et de feuillus de guaiacyl et de syringyle unités8,9. Des sources naturelles renouvelables, telles que les arbres et les plantes, sont souhaitables pour la production de monomères redessinés pour des matériaux polymères innovants10. Ces monomères, isolés et synthétisés à partir de sources naturelles, sont polymérisés en polymères dits biosourcés11.
Les acides carboxyliques aromatiques sont de plusieurs ordres de grandeur moins électrophiles que les acides carboxyliques aliphatiques équivalents pour des raisons électroniques12. Divers polyesters commerciaux utilisent des acides carboxyliques aromatiques au lieu d’acides carboxyliques aliphatiques. En conséquence, les fibres des textiles en polyester fabriqués à partir de fibres de poly(téréphtalate d’éthylène) (PET) sont presque insensibles à l’hydrolyse lors du lavage ou, par exemple, de la pluie13. Lorsque le recyclage moléculaire des polyesters est souhaité, il est conseillé d’utiliser des esters aliphatiques dans l’accumulation du polymère.
Pour les raisons mentionnées, nous avons étudié les possibilités de fabrication de polyesters à partir d’acides 4-hydroxy-3,5-diméthoxy-dihydrocinnamiques14. Des études antérieures de Kricheldorf15,Meier16et Miller17,18 montrent qu’il est difficile de construire des polymères en utilisant de l’acide 4-hydroxy-3,5-diméthoxy-dihydrocinnamique. La décarboxylation et la réticulation ont entravé les polymérisations, limitant ainsi le succès de ces synthèses. En outre, le mécanisme de la polycondensation restait incertain. L’article présenté décrit les conditions dans lesquelles le polyester poly(acide dihydrosinapinique) peut être synthétisé régulièrement et à haut rendement, ouvrant ainsi la voie à l’utilisation de polyesters semi-aromatiques recyclables moléculairement.
Nous avons développé un moyen vert et efficace de synthétiser l’acide sinapinique en utilisant une réaction de condensation entre le syringaldéhyde et l’acide malonique19,20. Après ce Knoevenagel vert, l’hydrogénation produit de l’acide dihydrosinapinique, qui convient à la polycondensation réversible. Cette publication visualise les étapes synthétiques du polymère moléculairement recyclable poly(acide dihydrosinapinique), en se référant aux unités de base de la lignine, appelée poly-S. Après avoir analysé le matériau polymère, le poly-S est dépolymérisé en acide dihydrosinapinique monomère dans des conditions relativement favorables et repolymérisé encore et encore.

<table>
	<tbody>
		<tr>
			<td>Reaction 1: Green Knoevenagel condensation</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Ammonium bicarbonate</td>
			<td>Sigma Aldrich</td>
			<td>&#62;99%</td>
			<td></td>
		</tr>
		<tr>
			<td>Ethanol</td>
			<td>Boom</td>
			<td>Technical grade</td>
			<td></td>
		</tr>
		<tr>
			<td>Ethyl acetate</td>
			<td>Macron</td>
			<td>99.8%</td>
			<td></td>
		</tr>
		<tr>
			<td>Hydrochloric acid</td>
			<td>Boom</td>
			<td>37%</td>
			<td></td>
		</tr>
		<tr>
			<td>Malonic acid</td>
			<td>Sigma Aldrich</td>
			<td>99%</td>
			<td>used as received</td>
		</tr>
		<tr>
			<td>Sodium bicarbonate</td>
			<td>Sigma Aldrich</td>
			<td>&#62;99.7%</td>
			<td></td>
		</tr>
		<tr>
			<td>Syringaldehyde</td>
			<td>Sigma Aldrich</td>
			<td>98%</td>
			<td>used as received</td>
		</tr>
		<tr>
			<td>Reaction 2: Hydrogenation</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Magnesium sulfate</td>
			<td>Macron</td>
			<td>99%</td>
			<td>dried</td>
		</tr>
		<tr>
			<td>Raney&#8482; nickel</td>
			<td>Sigma Aldrich</td>
			<td>&#62;89%</td>
			<td></td>
		</tr>
		<tr>
			<td>Sodium hydroxide</td>
			<td>Boom</td>
			<td>Technical grade</td>
			<td>dissolved</td>
		</tr>
		<tr>
			<td>Reaction 3: Acetylation</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Acetic anhydride</td>
			<td>Macron</td>
			<td>&#62;98%</td>
			<td></td>
		</tr>
		<tr>
			<td>Acetone</td>
			<td>Macron</td>
			<td>&#62;99.5%</td>
			<td></td>
		</tr>
		<tr>
			<td>Sodium acetate</td>
			<td>Sigma Aldrich</td>
			<td>&#62;99%</td>
			<td></td>
		</tr>
		<tr>
			<td>Reaction 4A: Polymerisation</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>1,2-xylene</td>
			<td>Macron</td>
			<td>&#62;98%</td>
			<td></td>
		</tr>
		<tr>
			<td>Sodium hydroxide</td>
			<td>Boom</td>
			<td>Technical grade</td>
			<td>finely powdered</td>
		</tr>
		<tr>
			<td>Zinc(II)acetate</td>
			<td>Sigma Aldrich</td>
			<td>99.99%</td>
			<td></td>
		</tr>
		<tr>
			<td>Reaction 4B: Depolymerisation</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Sodium hydroxide</td>
			<td>Boom</td>
			<td>Technical grade</td>
			<td>dissolved</td>
		</tr>
		<tr>
			<td>Sulfuric acid</td>
			<td>Macron</td>
			<td>100%</td>
			<td></td>
		</tr>
		<tr>
			<td>Analysis</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>CDCl3</td>
			<td>Cambride Isotope Laboratories, Inc.</td>
			<td>99.5%</td>
			<td></td>
		</tr>
		<tr>
			<td>CF3COOD</td>
			<td>Cambride Isotope Laboratories, Inc.</td>
			<td>98%</td>
			<td></td>
		</tr>
		<tr>
			<td>Dimethylformamide</td>
			<td>Macron</td>
			<td>&#62;99.9%</td>
			<td></td>
		</tr>
		<tr>
			<td>Hexafluoro-2-propanol</td>
			<td>TCI Chemicals</td>
			<td>&#62;99%</td>
			<td></td>
		</tr>
		<tr>
			<td>Methanol</td>
			<td>Macron</td>
			<td>&#62;99.8%</td>
			<td></td>
		</tr>
		<tr>
			<td>Tetrahydrofuran</td>
			<td>Macron</td>
			<td>&#62;99.9%</td>
			<td></td>
		</tr>
	</tbody>
</table>

designed for molecular recycling: a lignin-derived semi-aromatic biobased polymer

Le développement de biopolymères chimiquement recyclables offre des opportunités dans la poursuite d’une économie circulaire. Les biopolymères chimiquement recyclables font un effort positif pour résoudre le problème des matériaux polymères dans la phase d’élimination après la phase d’utilisation. Dans cet article, la production de polyesters semi-aromatiques biosourcés, qui peuvent être entièrement extraits de biomasse telle que la lignine, est décrite et visualisée. Le polymère poly-S décrit dans cet article a des propriétés thermiques similaires à celles de certains plastiques couramment utilisés, tels que le PET. Nous avons développé une réaction de Knoevenagel vert, qui peut produire efficacement des monomères à partir d’aldéhydes aromatiques et d’acide malonique. Cette réaction s’est avérée évolutive et a un facteur E calculé remarquablement bas. Ces polyesters avec des ligno-phytochimiques comme point de départ montrent un recyclage moléculaire efficace avec des pertes minimales. Le polyester poly(acide dihydrosinapinique) (poly-S) est présenté comme un exemple de ces polyesters semi-aromatiques, et la polymérisation, la dépolymérisation et la repolymérisation sont décrites.

L’acide sinapinique a été synthétisé en haute pureté et à haut rendement (> 95%) à partir de syringaldéhyde en utilisant la condensation green Knoevenagel. (Renseignements à l’appui : Figure S1) Le facteur E est une indication de la production de déchets où un nombre plus élevé indique plus de déchets. Le facteur E est calculé en prenant l’apport total de matière, en soustrayant la quantité du produit final souhaité et en divisant l’ensemble par la quantité du produit final. Ce...

Watch this Scientific Journal Video about Designed for Molecular Recycling: A Lignin-Derived Semi-aromatic Biobased Polymer at JoVE.com

Designed for Molecular Recycling: A Lignin-Derived Semi-aromatic Biobased Polymer

Un exemple d’approche en boucle fermée vers une économie circulaire des matériaux est décrit ici. Tout un cycle durable est présenté où les polyesters semi-aromatiques biosourcés sont conçus par polymérisation, dépolymérisation, puis repolymérisés avec seulement de légères modifications de leurs rendements ou de leurs propriétés finales.

Conçu pour le recyclage moléculaire : un polymère biosourcé semi-aromatique dérivé de la lignine

The development of chemically recyclable biopolymers offers opportunities within the pursuit of a circular economy. Chemically recyclable biopolymers make ...

Throughout the synthesis described in this paper provides a way to produce a new polymeric material specifically designed for molecular recycling, which is a way of chemical recycling. The depolarization and repolarization of the foreign material poly-S creates a fully sustainable cycle, which is a proof of concept for the future of polymers. The polymer waste of the world accumulates.For instance in the ocean, as the plastic soup, which could be prevented by introducing molecularly recyclable polymers. The polymer presented is an example of a polymeric material designed for molecular recycling. This in our opinion, should be implemented in other materials to prevent accumulation in nature.Green Knoevenagel reaction and subsequent steps have been designed for and by our undergraduated students. So certain robustness is already implemented in these reaction steps. The COVID-19 pandemic creates a situation where online learning becomes more important than ever.Visualization of these experiments helps us and others to deepen practical chemical education. Begin by adding 20.81 grams of malonic acid and 36.4 grams of syringaldehyde to a 215 milliliter round bottom flask. Dissolve both constituents in 20 milliliters of ethyl acetate and add 719 milligrams of ammonia bicarbonate to the flask.Mix and distill the solvent with a water bath. Keep the reaction mixture at 90 degrees Celsius for two hours in the open flask without stirring for complete conversion to sinapinic acid. In the work-up of the sinapinic acid product, dissolve the residue in 100 milliliters of a saturated aqueous sodium bicarbonate solution, then transfer the solution to a beaker, and acidify it to a pH two.Using six molar hydrogen chloride, separate the resulting residue by vacuum filtration and wash it with demineralized water. Charge a 450 milliliters flask with 33.6 grams sinapinic acid. Dissolve the sinapinic acid in 300 milliliters of two molar sodium hydroxide solution, and add 1.5 grams of nickel slurry before fitting the flask to the operators.Pressurize the reactor with three bar of hydrogen gas and mechanically shake the reaction at 80 degrees Celsius for three hours. Cool the reactor to room temperature and depressurize slowly. Recover most of the nickel catalyst with a magnet, then filter the solution.Acidify the solution with four molar hydrogen chloride solution to a pH of two, then perform an extraction with ethyl acetate. Remove the solvent under reduced pressure after drying over magnesium sulfate and dry the dihydrosinapinic acid at 60 degrees Celsius in a vacuum oven. Add 22.6 grams dihydrosinapinic acid to a 250 milliliter round bottom flask.Followed by 14.2 milliliters of acetic anhydride and 0.82 grams of sodium acetate. Heat the solution to 90 degrees Celsius while stirring for one hour for complete conversion of dihydrosinapinic acid to 4-Acetoxy-dihydrosinapinic acid, and it's acetylated oligomers. Dissolve the solid in 25 milliliters of acetone precipitated into 250 milliliters of 0.1 molar hydrogen chloride, then filtered on the vacuum.Add the monomers 20.8 grams of 4-Acetoxy-dihydrosinapinic acid and prepolymer to a 100 milliliter round bottom flask. Then add 400 milligrams of finely powdered sodium hydroxide, heat the reaction mixture for three hours at a set temperature of 140 degrees Celsius in the open flask while staring at 100 RPM. Set up a solvent assisted polymerization by adding 180 milligrams of zinc two acetate and 25.0 milliliters of 1, 2-xylene to the flask, then raise the set temperature to 160 degrees Celsius.Reflux the mixture at 144 degrees Celsius for three hours with constant water and acetic acid removal using Dean-Stark head. Cool the reaction mixture down and remove the 1, 2-xylene by applying a vacuum. Raise the temperature to 240 degrees Celsius during the final stage of the polymerization and apply a high vacuum for 30 minutes.Cool the polymer poly-S to room temperature and wash it with methanol to eliminate dihydrogen sinapinic acid and prepolymers. The obtained product should be a light brown solid. Finally grind and serve the poly-S into particles smaller than 180 micrometres to measure hydrolytic degradation.Load several test tubes with 20 milligrams of poly-S and add one milliliter of one molar sodium hydroxide solution. Incubate the tubes at three different temperatures with an agitation of 500 RPM. Neutralize the test tubes at regular time intervals with one milliliter of 0.5 molar sulfuric acid, and add two milliliters of methanol after cooling.Filter all samples using 0.45 micro meter PTFE syringe filters and inject 20 microliters into HPLC using an auto sampler. Monitor the absorbance at 254 nanometers and calculate the concentrations from a calibration curve of known dihydrosinapinic acid standard solutions. Sinapinic acid was synthesized in high purity and a greater than 95%yield from syringaldehyde using the Green Knoevenagel Condensation, the proposed mechanism of the step growth polymerization of 4-Acetoxy-dihydrosinapinic acid is shown here.Hydrogen one and MR measurements were taken during the polymerization process. When poly-S was hydrolyzed in sodium hydroxide, the molecularly recyclable polyester yielded the starting material dihydrosinapinic acid in less than 10 minutes. As confirmed by HBLC melting point analysis and hydrogen one and MR.Extended reaction times did not increase the yield.The thermal grams and GPC analysis of poly-S 1.0 and their successive generations poly-S 2.0 and polyester 3.0 after forced amorphicity with a tactic polystyrene are shown here. DSC analysis of poly-S shows a glass transition signal at 113 degrees Celsius and endothermic melting signal at 281 degrees Celsius. The polymers from re-polymerized sinapinic acid three eight poly-S 2.0 up and poly-H 3.0 exhibit similar thermal properties.Poly-S is a semi crystalline polymeric material because glass transition temperatures and melting signals are present in the thermograms of poly-S and their successive generations. GPC analysis after forced amorphicity with a tactic polystyrene displays a constant length of polymeric material throughout the different generations. While attempting the Green Knoevenagel reaction, please keep in mind that a correct temperature is used.A slightly higher temperature can lead to different site reactions. We have explored an example of a molecularly recyclable polymer. Closely related building blocks can follow the same procedure, or while maintaining thermal and mechanical properties.This method can be used in organic catalysis by demonstrating of the catalytic intermediates, as well in the still unexplored area of molecular recycling.

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