Knoevenagel Condensation for Modifying the Reducing End Groups of Cellulose Nanocrystals

Katja Heise; Tetyana Koso; Leena Pitkänen; Antje Potthast; Alistair W.T. King; Mauri A. Kostiainen; Eero Kontturi

doi:10.1021/acsmacrolett.9b00838

Knoevenagel Condensation for Modifying the Reducing End Groups of Cellulose Nanocrystals

Katja Heise
, Tetyana Koso
, Leena Pitkänen
, Antje Potthast
, Alistair W.T. King^*
, Mauri A. Kostiainen
, Eero Kontturi

^*Corresponding author for this work

Not published at VTT

Aalto University
University of Helsinki
University of Natural Resources and Life Sciences (BOKU)

Research output: Contribution to journal › Article › Scientific › peer-review

26 Citations (Scopus)

Abstract

Herein, we demonstrate an effective approach toward functionalization of cellulose nanocrystal (CNC) reducing ends by means of a Knoevenagel condensation reaction with a reactive β-diketone (acetylacetone). The end-wise modification was elucidated by advanced NMR analysis, which was facilitated by dissolving the CNCs in ionic liquid electrolyte and by the concomitant assignment of a model compound derived from d-cellobiose. The diffusion-edited ¹H experiment afforded a simple method to identify the assigned model resonances in the reducing end-modified CNCs. The condensations can be carried out in aqueous bicarbonate solutions, avoiding the use of hazardous solvents. Under these preliminary aqueous conditions, end-group conversion of up to 12.5% could be confirmed. These results demonstrate the potential of β-diketone chemistry and the Knoevenagel condensation for functionalizing cellulose reducing ends. Application of this liquid-state NMR method for confirming and quantifying reducing end conversion is also shown to be invaluable. Extension of this chemistry to other 1,3-dicarbonyl compounds and solvation conditions should allow for the topochemical and (axially) chirotopic installation of functional moieties to CNCs, paving the way to asymmetric cellulose-based nanomaterials with unique properties.

Original language	English
Pages (from-to)	1642-1647
Journal	ACS Macro Letters
Volume	8
Issue number	12
DOIs	https://doi.org/10.1021/acsmacrolett.9b00838
Publication status	Published - 17 Dec 2019
MoE publication type	A1 Journal article-refereed

Funding

K.H. and E.K. gratefully acknowledge the FinnCERES program enabled by the Academy of Finland, Aalto University, and VTT. A.K. and T.K. would like to acknowledge the Academy of Finland for funding under the Project “WTF-Click-Nano” (311255). The authors gratefully acknowledge Mrs. Rita Hatakka for carrying out SEC measurements and the CSC – IT Center for Science, Finland, for computational resources. This work made use of Aalto University’s Bioeconomy Facilities and the FinnCERES ecosystem.

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10.1021/acsmacrolett.9b00838

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title = "Knoevenagel Condensation for Modifying the Reducing End Groups of Cellulose Nanocrystals",

abstract = "Herein, we demonstrate an effective approach toward functionalization of cellulose nanocrystal (CNC) reducing ends by means of a Knoevenagel condensation reaction with a reactive β-diketone (acetylacetone). The end-wise modification was elucidated by advanced NMR analysis, which was facilitated by dissolving the CNCs in ionic liquid electrolyte and by the concomitant assignment of a model compound derived from d-cellobiose. The diffusion-edited 1H experiment afforded a simple method to identify the assigned model resonances in the reducing end-modified CNCs. The condensations can be carried out in aqueous bicarbonate solutions, avoiding the use of hazardous solvents. Under these preliminary aqueous conditions, end-group conversion of up to 12.5\% could be confirmed. These results demonstrate the potential of β-diketone chemistry and the Knoevenagel condensation for functionalizing cellulose reducing ends. Application of this liquid-state NMR method for confirming and quantifying reducing end conversion is also shown to be invaluable. Extension of this chemistry to other 1,3-dicarbonyl compounds and solvation conditions should allow for the topochemical and (axially) chirotopic installation of functional moieties to CNCs, paving the way to asymmetric cellulose-based nanomaterials with unique properties.",

author = "Katja Heise and Tetyana Koso and Leena Pitk{\"a}nen and Antje Potthast and King, \{Alistair W.T.\} and Kostiainen, \{Mauri A.\} and Eero Kontturi",

note = "Funding Information: K.H. and E.K. gratefully acknowledge the FinnCERES program enabled by the Academy of Finland, Aalto University, and VTT. A.K. and T.K. would like to acknowledge the Academy of Finland for funding under the Project “WTF-Click-Nano” (311255). The authors gratefully acknowledge Mrs. Rita Hatakka for carrying out SEC measurements and the CSC – IT Center for Science, Finland, for computational resources. This work made use of Aalto University{\textquoteright}s Bioeconomy Facilities and the FinnCERES ecosystem. Publisher Copyright: Copyright {\textcopyright} 2019 American Chemical Society.",

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AU - Heise, Katja

AU - Koso, Tetyana

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AU - Potthast, Antje

AU - King, Alistair W.T.

AU - Kostiainen, Mauri A.

AU - Kontturi, Eero

N1 - Funding Information: K.H. and E.K. gratefully acknowledge the FinnCERES program enabled by the Academy of Finland, Aalto University, and VTT. A.K. and T.K. would like to acknowledge the Academy of Finland for funding under the Project “WTF-Click-Nano” (311255). The authors gratefully acknowledge Mrs. Rita Hatakka for carrying out SEC measurements and the CSC – IT Center for Science, Finland, for computational resources. This work made use of Aalto University’s Bioeconomy Facilities and the FinnCERES ecosystem. Publisher Copyright: Copyright © 2019 American Chemical Society.

PY - 2019/12/17

Y1 - 2019/12/17

N2 - Herein, we demonstrate an effective approach toward functionalization of cellulose nanocrystal (CNC) reducing ends by means of a Knoevenagel condensation reaction with a reactive β-diketone (acetylacetone). The end-wise modification was elucidated by advanced NMR analysis, which was facilitated by dissolving the CNCs in ionic liquid electrolyte and by the concomitant assignment of a model compound derived from d-cellobiose. The diffusion-edited 1H experiment afforded a simple method to identify the assigned model resonances in the reducing end-modified CNCs. The condensations can be carried out in aqueous bicarbonate solutions, avoiding the use of hazardous solvents. Under these preliminary aqueous conditions, end-group conversion of up to 12.5% could be confirmed. These results demonstrate the potential of β-diketone chemistry and the Knoevenagel condensation for functionalizing cellulose reducing ends. Application of this liquid-state NMR method for confirming and quantifying reducing end conversion is also shown to be invaluable. Extension of this chemistry to other 1,3-dicarbonyl compounds and solvation conditions should allow for the topochemical and (axially) chirotopic installation of functional moieties to CNCs, paving the way to asymmetric cellulose-based nanomaterials with unique properties.

AB - Herein, we demonstrate an effective approach toward functionalization of cellulose nanocrystal (CNC) reducing ends by means of a Knoevenagel condensation reaction with a reactive β-diketone (acetylacetone). The end-wise modification was elucidated by advanced NMR analysis, which was facilitated by dissolving the CNCs in ionic liquid electrolyte and by the concomitant assignment of a model compound derived from d-cellobiose. The diffusion-edited 1H experiment afforded a simple method to identify the assigned model resonances in the reducing end-modified CNCs. The condensations can be carried out in aqueous bicarbonate solutions, avoiding the use of hazardous solvents. Under these preliminary aqueous conditions, end-group conversion of up to 12.5% could be confirmed. These results demonstrate the potential of β-diketone chemistry and the Knoevenagel condensation for functionalizing cellulose reducing ends. Application of this liquid-state NMR method for confirming and quantifying reducing end conversion is also shown to be invaluable. Extension of this chemistry to other 1,3-dicarbonyl compounds and solvation conditions should allow for the topochemical and (axially) chirotopic installation of functional moieties to CNCs, paving the way to asymmetric cellulose-based nanomaterials with unique properties.

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M3 - Article

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EP - 1647

JO - ACS Macro Letters

JF - ACS Macro Letters

IS - 12

ER -

Knoevenagel Condensation for Modifying the Reducing End Groups of Cellulose Nanocrystals

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