Name: designed for molecular recycling: a lignin-derived semi-aromatic biobased polymer
Uploaded: 2020-11-30T14:00:00
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Gli autori sono grati per il sostegno finanziario dell'Organizzazione olandese per la ricerca scientifica (NWO) (sovvenzione 023.007.020 assegnata a Jack van Schijndel).

1. Condensazione di Knoevenagel verde della siringaldeide verso acido sinapinico con bicarbonato di ammonio al 5 mol%
<ol><li>Aggiungere acido malonico (20,81 g, 200,0 mmol) insieme a siringaldeide (36,4 g, 200,0 mmol) in un matraccio a fondo tondo da 250 ml. Sciogliere entrambi i costituenti in 20,0 mL di acetato di etile e aggiungere bicarbonato di ammonio (790 mg, 10,0 mmol) al matraccio. NOTA: Per garantire il pieno completamento della reazione di condensazione, l'evaporatore rotativo può essere utilizzato per ...

<ol>
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LC-copolyesters of 3-(4-hydroxyphenyl) propionic acid and 4-hydroxy benzoic acids.</a> Journal of Polymer Science Part A: Polymer Chemistry. 25 (2), 489-504 (1987).</li><li>Chen, Y., Tan, L., Chen, L., Yang, Y., Wang, X. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Study+on+biodegradable+aromatic/aliphatic+copolyesters.">Study on biodegradable aromatic/aliphatic copolyesters.</a> Brazilian Journal of Chemical Engineering. 25 (2), 321-335 (2008).</li><li>Han, X., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+Change+in+Mechanism+from+Acidolysis+to+Phenolysis+in+the+Bulk+Copolymerization+of+4-Acetoxybenzoic+Acid+and+6-Acetoxy-2-naphthoic+Acid.">A Change in Mechanism from Acidolysis to Phenolysis in the Bulk Copolymerization of 4-Acetoxybenzoic Acid and 6-Acetoxy-2-naphthoic Acid.</a> Macromolecules. 29 (26), 8313-8320 (1996).</li><li>Lu, X. 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Quando l'acido diidrosinapinico è stato riscaldato in un recipiente di reazione, si è verificata la sublimazione del materiale di partenza e questo effetto è stato migliorato quando è stato applicato un vuoto. L'acetilazione è stata eseguita sull'acido diidrosinapinico per evitare la sublimazione. Kricheldorf et al.12,27 hanno riconosciuto che non solo l'acetilazione, ma si è verificata in modo simile di- e oligomerizzazione. Tuttavia, questi monomeri e oli...

A differenza dell'incenerimento dei rifiuti polimerici, il riciclaggio chimico offre la possibilità di recuperare i monomeri. Il riciclaggio chimico è una scelta logica alla fine della vita tecnica dei materiali polimerici poiché questi materiali polimerici sono prodotti chimicamente1. Esistono due modi per riciclare chimicamente il materiale polimerico, la pirolisi e il riciclaggio molecolare2. Con la pirolisi, il materiale polimerico viene trasformato in prodotti di valore superiore utilizzando condizioni estreme3,4. Il riciclaggio molecolare è un metodo efficace per recuperare i materiali di partenza utilizzando la depolimerizzazione. Dopo la depolimerizzazione, le unità monomeriche possono essere ripolimerizzate in materiali polimerici vergini5. La disponibilità di monomeri adatti per applicare il riciclaggio molecolare su una scala più ampia è carente. L'attuale problema della plastica impone che la società richieda materiali polimerici robusti e robusti. Allo stesso tempo, è anche preferibile che gli stessi materiali polimerici siano facilmente riciclabili e non resistano nell'ambiente. Gli attuali materiali polimerici con buone proprietà termiche e meccaniche non si depolimerizzano facilmente6.
La lignina, che si trova comunemente nelle piante vascolari, è responsabile del 30% del contenuto naturale di carbonio del mondo ed è il secondo biopolimero più abbondante dopo la cellulosa. La lignina ha una complessa struttura amorfa e sembra essere un'alternativa adatta per sostituire gli aromatici estratti da materiali fossili. La struttura tridimensionale della lignina fornisce resistenza e rigidità al legno, nonché resistenza al degrado. Chimicamente parlando, la lignina è un termoinduro polifenolico molto complesso. Consiste in una composizione variabile di tre diverse strutture di fenilpropano metossilato. Siringile, guaiacile e p-idrossifenile (spesso abbreviati rispettivamente in S, G e H) sono derivati dai monolignoli dell'alcol sinapilico, dell'alcol coniferilico e dell'alcol p-cumarilico7. La distribuzione di queste unità varia a seconda del tipo di biomassa, con legno tenero, ad esempio, costituito per lo più da unità guaiaciliche e legno duro di unità guaiacil e siringiliche8,9. Le fonti naturali rinnovabili, come alberi e piante, sono auspicabili per la produzione di monomeri riprogettati per materiali polimerici innovativi10. Questi monomeri, isolati e sintetizzati da fonti naturali, sono polimerizzati ai cosiddetti polimeri biobased11.
Gli acidi carbossilici aromatici sono diversi ordini di grandezza meno elettrofili degli equivalenti acidi carbossilici alifatici per ragioni elettroniche12. Vari poliesteri commerciali utilizzano acidi carbossilici aromatici invece di acidi carbossilici alifatici. Di conseguenza, le fibre nei tessuti in poliestere a base di fibre di poli (etilene tereftalato) (PET) sono quasi insensibili all'idrolisi durante il lavaggio o, ad esempio, la pioggia13. Quando si desidera il riciclaggio molecolare dei poliesteri, è consigliabile utilizzare esteri alifatici nell'accumulo del polimero.
Per i motivi menzionati, abbiamo studiato le possibilità di produrre poliesteri da acidi 4-idrossi-3,5-dimetossi-diidrocinnamici14. Precedenti studi di Kricheldorf15,Meier16e Miller17,18 mostrano che è difficile costruire polimeri usando acido 4-idrossi-3,5-dimetossi-diidrocinnamico. La decarbossilazione e la reticolazione ostacolarono le polimerizzazioni, limitando così il successo di queste sintesi. Inoltre, il meccanismo della policodensazione è rimasto poco chiaro. Il documento presentato descrive le condizioni in cui il poliestere poli(acido diidrosinapinico) può essere sintetizzato regolarmente e ad alta resa, aprendo così la strada all'utilizzo di poliesteri semi-aromatici che sono riciclabili molecolarmente.
Abbiamo sviluppato un modo verde ed efficiente per sintetizzare l'acido sinapinico utilizzando una reazione di condensazione tra siringaldeide e acido malonico19,20. Dopo questo Knoevenagel verde, l'idrogenazione produce acido diidrosinapinico, che è adatto per la policodensazione reversibile. Questa pubblicazione visualizza i passaggi sintetici del polimero polimerico riciclabile molecolarmente poli(acido diidrosinapinico), riferendosi alle unità di base della lignina, chiamate poly-S. Dopo aver analizzato il materiale polimerico, il poly-S viene depolimerizzato nell'acido monomero diidrosinapinico in condizioni relativamente favorevoli e ripolimerizzato più e più volte.

<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

Lo sviluppo di biopolimeri chimicamente riciclabili offre opportunità nel perseguimento di un'economia circolare. I biopolimeri chimicamente riciclabili fanno uno sforzo positivo per risolvere il problema dei materiali polimerici nella fase di smaltimento dopo la fase di utilizzo. In questo articolo, viene descritta e visualizzata la produzione di poliesteri semi-aromatici biobased, che possono essere estratti interamente da biomasse come la lignina. Il polimero poly-S descritto in questo documento ha proprietà termiche simili a certe plastiche comunemente usate, come il PET. Abbiamo sviluppato una reazione di Knoevenagel verde, che può produrre in modo efficiente monomeri da aldeidi aromatiche e acido malonico. Questa reazione ha dimostrato di essere scalabile e ha un fattore E calcolato notevolmente basso. Questi poliesteri con ligno-fitochimici come punto di partenza mostrano un efficiente riciclo molecolare con perdite minime. Il poliestere poli(acido diidrosinapinico) (poly-S) è presentato come un esempio di questi poliesteri semi-aromatici e vengono descritte la polimerizzazione, la depolimerizzazione e la ripolimerizzazione.

L'acido sinapinico è stato sintetizzato in alta purezza e ad alta resa (> 95%) dalla siringaldeide utilizzando la condensazione Green Knoevenagel. (Informazioni di supporto: Figura S1) Il fattore E è un'indicazione della produzione di rifiuti in cui un numero maggiore indica più rifiuti. Il fattore E viene calcolato prendendo l'input materiale totale, sottraendo la quantità del prodotto finale desiderato e dividendo il tutto per la quantità del prodotto finale. Questa condensazione di Knoevenagel ve...

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 esempio di approccio a circuito chiuso verso un'economia circolare dei materiali è descritto qui. Viene presentato un intero ciclo sostenibile in cui i poliesteri semi-aromatici biobased sono progettati mediante polimerizzazione, depolimerizzazione e quindi ripolimerizzati con solo lievi cambiamenti nelle loro rese o proprietà finali.

Progettato per il riciclaggio molecolare: un polimero biobased semi-aromatico derivato dalla lignina

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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&alpha;-Carbon Chemistry: Enols, Enolates, and Enamines

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Ricerca

Chimica

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Functionalization of Single-walled Carbon Nanotubes with Thermo-reversible Block Copolymers and Characterization by Small-angle Neutron Scattering

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The Preparation and Properties of Thermo-reversibly Cross-linked Rubber Via Diels-Alder Chemistry

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Microfluidic Dry-spinning and Characterization of Regenerated Silk Fibroin Fibers

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Electrochemical impedance spectroscopy (EIS) was used for advanced characterization of organic electroactive compounds along with cyclic voltammetry (CV). ...

Time-resolved Photophysical Characterization of Triplet-harvesting Organic Compounds at an Oxygen-free Environment Using an iCCD Camera

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