Name: designed for molecular recycling: a lignin-derived semi-aromatic biobased polymer
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Forfatterne er takknemlige for den økonomiske støtten fra Den nederlandske organisasjonen for vitenskapelig forskning (NWO) (tilskudd 023.007.020 tildelt Jack van Schijndel).

1. Grønn Knoevenagel kondensering av syringaldehyd mot sinapinsyre med 5 mol% ammoniumbikarbonat
<ol><li>Tilsett malonsyre (20,81 g, 200,0 mmol) sammen med syringaldehyd (36,4 g, 200,0 mmol) til en 250 ml rundbunnsflaske. Løs opp begge bestanddelene i 20,0 ml etylacetat og tilsett ammoniumbikarbonat (790 mg, 10,0 mmol) i kolben. MERK: For å sikre full fullføring av kondensreaksjonen, kan den roterende fordamperen brukes til å destillere etylacetatet og konsentrere reaksjonsblandingen, noe som resulterer i en l?...

<ol>
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A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Biorenewable+polyethylene+terephthalate+mimics+derived+from+lignin+and+acetic+acid.">Biorenewable polyethylene terephthalate mimics derived from lignin and acetic acid.</a> Green Chemistry. 12 (10), 1704 (2010).</li><li>Nguyen, H. T. H., Reis, M. H., Qi, P., Miller, S. A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Polyethylene+ferulate+(PEF)+and+congeners:+polystyrene+mimics+derived+from+biorenewable+aromatics.">Polyethylene ferulate (PEF) and congeners: polystyrene mimics derived from biorenewable aromatics.</a> Green Chemistry. 17 (9), 4512-4517 (2015).</li><li>van Schijndel, J., Canalle, L. A., Molendijk, D., 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=The+Green+Knoevenagel+Condensation:+Solvent-free+Condensation+of+Benzaldehydes.">The Green Knoevenagel Condensation: Solvent-free Condensation of Benzaldehydes.</a> Green Chemistry Letters and Reviews. 10 (4), 404-411 (2017).</li><li>van Schijndel, J., Molendijk, D., Spakman, H., Knaven, E., Canalle, L. 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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R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Effect+of+polystyrene+on+poly(ethylene+terephthalate)+crystallization.">Effect of polystyrene on poly(ethylene terephthalate) crystallization.</a> Materials Research. 17 (6), 1620-1627 (2014).</li><li>Kricheldorf, H. R., Conradi, A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=New+polymer+syntheses+16.+LC-copolyesters+of+3-(4-hydroxyphenyl)+propionic+acid+and+4-hydroxy+benzoic+acids.">New polymer syntheses 16. 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 ble oppvarmet i et reaksjonsbeholder, oppstod sublimering av startmaterialet, og denne effekten ble forbedret når et vakuum ble påført. Acetylering har blitt utført på dihydrosinapinsyre for å unngå sublimering. Kricheldorf et al.12,27 erkjente at ikke bare acetylering, men tilsvarende di- og oligomerisering skjedde. Imidlertid er disse esterifiserte monomerer og oligomerer ikke lenger sublime og er egnet som monomerer for smeltepol...

I motsetning til forbrenning av polymeravfall, gir kjemisk resirkulering muligheten til å gjenopprette monomerene. Kjemisk resirkulering er et logisk valg på slutten av den tekniske levetiden til polymere materialer siden disse polymere materialene produseres kjemisk1. Det er to måter å resirkulere polymermaterialet kjemisk, pyrolyse og molekylær resirkulering2. Med pyrolyse omdannes det polymere materialet til produkter med høyere verdi ved å bruke ekstreme forhold3,4. Molekylær resirkulering er en effektiv metode for å gjenvinne startmaterialene ved hjelp av depolymerisering. Etter depolymerisering kan de monomeriske enhetene repolymeriseres til jomfruelige polymere materialer5. Tilgjengeligheten av egnede monomerer for å påføre molekylær resirkulering i større skala er ønsket. Det nåværende plastproblemet tilsier at samfunnet krever solide og robuste polymere materialer. Samtidig er det også foretrukket at de samme polymere materialene er lett resirkulerbare og ikke tåler i miljøet. Nåværende polymere materialer med gode termiske og mekaniske egenskaper depolymererer ikke lett6.
Lignin, ofte funnet i vaskulære planter, er ansvarlig for 30% av verdens naturlige karboninnhold og er den nest mest tallrike biopolymeren etter cellulose. Lignin har en kompleks amorf struktur og ser ut til å være et passende alternativ for å erstatte aromatikk ekstrahert fra fossile materialer. Lignins tredimensjonale struktur gir styrke og stivhet til tre, samt motstand mot nedbrytning. Kjemisk sett er lignin et svært komplekst polyfenolisk termosett. Den består av varierende sammensetning av tre forskjellige metoksylerte fenylpropanstrukturer. Syringyl, guaiacyl og p-hydroksyfenyl (ofte forkortet som henholdsvis S, G og H) er avledet fra monolignols sinapylalkohol, nåletylalkohol og p-coumarylalkohol7. Fordelingen av disse enhetene varierer per biomassetype, med mykved, for eksempel bestående av for det meste guaiacylenheter og hardved av guaiacyl- og syringylenheter8,9. Fornybare naturlige kilder, som trær og planter, er ønskelige for produksjon av redesignede monomerer for innovative polymere materialer10. Disse monomerene, isolert og syntetisert fra naturlige kilder, polymeriseres til såkalte biobaserte polymerer11.
Aromatiske karboksylsyrer er flere størrelsesordener mindre elektrofile enn de tilsvarende alifatiske karboksylsyrene av elektroniske grunner12. Ulike kommersielle polyestere bruker aromatiske karboksylsyrer i stedet for alifatiske karboksylsyrer. Som et resultat er fibrene i polyestertekstiler laget av poly (etylentereftalat) (PET) fibre nesten ufølsomme for hydrolyse under vask eller for eksempel regn13. Når molekylær resirkulering av polyester er ønsket, anbefales det å bruke alifatiske estere i oppbyggingen av polymeren.
Av de nevnte grunnene har vi undersøkt mulighetene for å lage polyester fra 4-hydroksy-3,5-dimetoksy-dihydrocinnamic syrer14. Tidligere studier av Kricheldorf15, Meier16og Miller17,18 viser at det er utfordrende å bygge polymerer ved hjelp av 4-hydroksy-3,5-dimetoksy-dihydrocinnamic acid. Dekarboksylering og krysskobling hindret polymerisasjonene, og begrenset dermed suksessen til disse syntesene. Også mekanismen for polykondensasjonen forble uklar. Det presenterte papiret beskriver forholdene der polyesterpolyen (dihydrosinapinsyre) kan syntetiseres regelmessig og i høyt utbytte, og dermed bane vei for bruk av semi-aromatiske polyestere som er molekylært resirkulerbare.
Vi har utviklet en grønn og effektiv måte å syntetisere sinapinsyre ved hjelp av en kondensreaksjon mellom syringaldehyd og malonsyre19,20. Etter denne grønne Knoevenagel produserer hydrogenering dihydrosinapinsyre, som er egnet for reversibel polykondensasjon. Denne publikasjonen visualiserer de syntetiske trinnene til den molekylært resirkulerbare polymerpolyen (dihydrosinapinsyre), med henvisning til baseenhetene til lignin, kalt poly-S. Etter å ha analysert det polymere materialet, blir poly-S depolymerisert til monomer dihydrosinapinsyre under relativt gunstige forhold og repolymerisert om og om igjen.

<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

Utviklingen av kjemisk resirkulerbare biopolymerer gir muligheter i jakten på en sirkulær økonomi. Kjemisk resirkulerbare biopolymerer gjør en positiv innsats for å løse problemet med polymermaterialer i avhendingsfasen etter bruksfasen. I dette papiret beskrives og visualiseres produksjonen av biobaserte semi-aromatiske polyestere, som kan ekstraheres helt fra biomasse som lignin. Polymerpoly-S beskrevet i dette papiret har termiske egenskaper som ligner på visse vanlige plast, for eksempel PET. Vi utviklet en Grønn Knoevenagel-reaksjon, som effektivt kan produsere monomerer fra aromatiske aldehyder og malonsyre. Denne reaksjonen har vist seg å være skalerbar og har en bemerkelsesverdig lav beregnet E-faktor. Disse polyestere med ligno-fytokjemikalier som utgangspunkt viser en effektiv molekylær resirkulering med minimal tap. Polyesterpolyen (dihydrosinapinsyre) (poly-S) presenteres som et eksempel på disse semi-aromatiske polyestere, og polymerisering, depolymerisering og repolymerisering er beskrevet.

Sinapinsyre ble syntetisert i høy renhet og høyt utbytte (> 95%) fra syringaldehyd ved hjelp av den grønne Knoevenagel-kondensasjonen. (Støtteinformasjon: Figur S1) E-faktoren er en indikasjon på avfallsproduksjon der et høyere antall indikerer mer avfall. E-faktoren beregnes ved å ta den totale materialinngangen, trekke fra mengden av ønsket sluttprodukt og dele helheten med mengden sluttprodukt. Denne grønne Knoevenagel-kondensen har en E-faktor på 1,0, som kan beregnes: [((29,81 g malonsyre ...

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 sløyfe tilnærming til en sirkulær materialøkonomi er beskrevet her. En hel bærekraftig syklus presenteres der biobaserte semi-aromatiske polyestere er designet av polymerisering, depolymerisering, og deretter re-polymerisert med bare små endringer i utbyttet eller endelige egenskaper.

Designet for molekylær resirkulering: En Lignin-avledet semi-aromatisk biobasert 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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