Name: designed for molecular recycling: a lignin-derived semi-aromatic biobased polymer
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Forfatterne er taknemmelige for den økonomiske støtte fra Den Nederlandske Organisation for Videnskabelig Forskning (NWO) (tilskud 023.007.020 tildelt Jack van Schijndel).

1. Grøn Knoevenagel kondensering af syringaldehyd mod sinapinsyre med 5 mol% ammoniumbicarbonat
<ol><li>Der tilsættes æblesyre (20,81 g, 200,0 mmol) sammen med syringaldehyd (36,4 g, 200,0 mmol) til en 250 mL rundbundet kolbe. Begge bestanddele opløses i 20,0 ml ethylacetat, og der tilsættes ammoniumbicarbonat (790 mg, 10,0 mmol) til kolben. BEMÆRK: For at sikre fuld afslutning af kondensreaktionen kan den roterende fordamper bruges til at destillere ethylacetat og koncentrere reaktionsblandingen, hvilket resu...

<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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Når dihydrosinapinsyre blev opvarmet i et reaktionskar, opstod sublimering af udgangsmaterialet, og denne effekt blev forbedret, når der blev påført et vakuum. Acetylation er blevet udført på dihydrosinapinsyre for at undgå sublimering. Kricheldorf et al.12,27 erkendte, at ikke kun acetylation, men tilsvarende di- og oligomerisering fandt sted. Disse esterificerede monomerer og oligomerer sublimerer dog ikke længere og er egnede som monomerer til smeltepo...

I modsætning til forbrænding af polymert affald giver kemisk genanvendelse mulighed for at genvinde monomererne. Kemisk genanvendelse er et logisk valg i slutningen af polymermaterialernes tekniske levetid, da disse polymere materialer produceres kemisk1. Der er to måder at genbruge det polymere materiale kemisk, pyrolyse og molekylær genanvendelse2. Med pyrolyse omdannes det polymere materiale til produkter af højere værdi ved hjælp af ekstreme forhold3,4. Molekylær genanvendelse er en effektiv metode til genvinding af udgangsmaterialerne ved hjælp af depolymerisering. Efter depolymerisering kan de monomeriske enheder repolymeriseres til jomfru polymere materialer5. Tilgængeligheden af egnede monomerer til at anvende molekylær genanvendelse i større skala er mangelfuld. Det nuværende plastproblem dikterer, at samfundet kræver robuste og robuste polymere materialer. Samtidig foretrækkes det også, at de samme polymere materialer er let genanvendelige og ikke holder ud i miljøet. Nuværende polymere materialer med gode termiske og mekaniske egenskaber depolymerize let6.
Lignin, der almindeligvis findes i vaskulære planter, er ansvarlig for 30% af verdens naturlige kulstofindhold og er den næstmest rigelige biopolymer efter cellulose. Lignin har en kompleks amorf struktur og synes at være et egnet alternativ til at erstatte aromater udvundet af fossile materialer. Den tredimensionelle struktur af lignin giver styrke og stivhed til træ, samt modstandsdygtighed over for nedbrydning. Kemisk set er lignin et meget komplekst polyphenolic termosæt. Den består af varierende sammensætning af tre forskellige methoxylated phenylpropan strukturer. Syringyl, guaiacyl og p-hydroxyphenyl (ofte forkortet som henholdsvis S, G og H) er afledt af monolignols sinapylalkohol, nåletræsalkohol og p-coumarylalkohol7. Fordelingen af disse enheder varierer pr . biomassetype,f.eks. Vedvarende naturlige kilder, såsom træer og planter, er ønskelige til produktion af redesignede monomerer til innovative polymere materialer10. Disse monomerer, isolerede og syntetiseret fra naturlige kilder, polymeriseres til såkaldte biobaserede polymerer11.
Aromatiske carboxylic syrer er flere størrelsesordener mindre elektrofile end de tilsvarende alifatiske carboxylic syrer af elektroniske årsager12. Forskellige kommercielle polyestere bruger aromatiske carboxylic syrer i stedet for alifatiske carboxylic syrer. Som følge heraf er fibrene i polyestertekstiler fremstillet af poly (ethylenterephthalat) (PET) fibre næsten ufølsomme over for hydrolyse under vask eller for eksempel regn13. Når den molekylære genanvendelse af polyester er ønsket, er det tilrådeligt at bruge alifatiske estere i opbygningen af polymeren.
Af de nævnte grunde har vi undersøgt mulighederne for at lave polyester fra 4-hydroxy-3,5-dimethoxy-dihydrocinnamsyrer14. Tidligere undersøgelser af Kricheldorf15,Meier16, og Miller17,18 viser, at det er udfordrende at bygge polymerer ved hjælp af 4-hydroxy-3,5-dimethoxy-dihydrocinnamic syre. Decarboxylation og crosslinking hindrede polymeriseringerne og begrænsede dermed succesen af disse syntheser. Polykondensationens mekanisme forblev også uklar. Det præsenterede papir beskriver de betingelser, hvorunder polyester poly (dihydrosinapinsyre) kan syntetiseres regelmæssigt og med højt udbytte, hvilket baner vejen for brug af semi-aromatiske polyestere, der er molekylært genanvendelige.
Vi har udviklet en grøn og effektiv måde at syntetisere sinapinsyre ved hjælp af en kondensreaktion mellem syringaldehyd og malonsyre19,20. Efter denne Grønne Knoevenagel producerer hydrogenering dihydrosinapinsyre, som er egnet til reversibel polykondensering. Denne publikation visualiserer de syntetiske trin til den molekylært genanvendelige polymer poly (dihydrosinapinsyre), med henvisning til basisenhederne af lignin, kaldet poly-S. Efter at have analyseret det polymere materiale afkalkes poly-S til monomer dihydrosinapinsyre under relativt gunstige forhold og repolymeriseres igen og igen.

<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

Udviklingen af kemisk genanvendelige biopolymers giver muligheder i jagten på en cirkulær økonomi. Kemisk genanvendelige biopolymører gør en positiv indsats for at løse problemet med polymermaterialer i bortskaffelsesfasen efter brugsfasen. I dette papir beskrives og visualiseres produktionen af biobaserede halv aromatiske polyestere, som udelukkende kan udvindes fra biomasse som lignin. Polymer poly-S beskrevet i dette papir har termiske egenskaber svarende til visse almindeligt anvendte plast, såsom PET. Vi udviklede en Grøn Knoevenagel reaktion, som effektivt kan producere monomerer fra aromatiske aldehyder og æblesyre. Denne reaktion har vist sig at være skalerbar og har en bemærkelsesværdig lav beregnet E-faktor. Disse polyestere med ligno-fytokemikalier som udgangspunkt viser en effektiv molekylær genanvendelse med minimale tab. Polyester poly (dihydrosinapinsyre) (poly-S) præsenteres som et eksempel på disse semi-aromatiske polyester, og polymerisering, depolymerisering, og re-polymerisering er beskrevet.

Sinapinsyre blev syntetiseret i høj renhed og højt udbytte (> 95%) fra syringaldehyd ved hjælp af Green Knoevenagel kondens. (Supplerende oplysninger: Figur S1) E-faktoren er en indikation af affaldsproduktion, hvor et højere antal angiver mere affald. E-faktoren beregnes ved at tage det samlede materialeinput, trække mængden af det ønskede slutprodukt fra og dividere helheden med mængden af slutproduktet. Denne grønne Knoevenagel kondens har en E-faktor på 1,0, som kan beregnes: [((29,81 g mal...

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

Et eksempel på en lukket tilgang til en cirkulær materialeøkonomi er beskrevet her. En hel bæredygtig cyklus præsenteres, hvor biobaserede semi-aromatiske polyestere er designet ved polymerisering, depolymerisering, og derefter re-polymeriseret med kun små ændringer i deres udbytter eller endelige egenskaber.

Designet til molekylær genanvendelse: En lignin-afledt semi-aromatisk biobaseret polymer

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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