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

Research output: Contribution to journalArticleScientificpeer-review

19 Citations (Scopus)


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 languageEnglish
Pages (from-to)1642-1647
JournalACS Macro Letters
Issue number12
Publication statusPublished - 17 Dec 2019
MoE publication typeA1 Journal article-refereed


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