Wet esterification of never-dried cellulose: a simple process to surface-acetylated cellulose nanofibers

Beaumont, Marco; Winklehner, Stefan; Veigel, Stefan; Mundigler, Norbert; Gindl‐Altmutter, Wolfgang; Potthast, Antje; Rosenau, Thomas

doi:10.1039/d0gc02116d

Cited by 53 publications

(70 citation statements)

References 37 publications

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“…This efficiency is remarkable for a bulk solvent-free and heterogeneous reaction (but still containing significant surface water). It is significantly higher than the solvent-based acetylation of cellulose with N-acetylimidazole 44 and comparable to the most efficient acetylations of cellulose under homogeneous conditions 65,66 . While increasing the amount of N-acetylimidazole decreases the reaction efficiency and the reaction rate (Supplementary Table 2 and Supplementary Fig.…”

Section: Control Of Chemical Accessibility and Effect On Bulk Propertiesmentioning

confidence: 80%

“…The number of water molecules is in the same stoichiometric range as that of the cellulose´s surface hydroxyl groups and hence water is strongly bound to the surface. In this work, we used solely the solid reactant, N-acetylimidazole [41][42][43][44] and a catalyst, imidazole, to acetylate the cellulose surface. Imidazole was chosen because of its structural analogy to histidine, its associated enzyme-like catalytic behaviour 45 and affinity for cellulose surfaces 46 .…”

Section: Resultsmentioning

confidence: 99%

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Unique reactivity of nanoporous cellulosic materials mediated by surface-confined water

et al. 2021

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The remarkable efficiency of chemical reactions is the result of biological evolution, often involving confined water. Meanwhile, developments of bio-inspired systems, which exploit the potential of such water, have been so far rather complex and cumbersome. Here we show that surface-confined water, inherently present in widely abundant and renewable cellulosic fibres can be utilised as nanomedium to endow a singular chemical reactivity. Compared to surface acetylation in the dry state, confined water increases the reaction rate and efficiency by 8 times and 30%, respectively. Moreover, confined water enables control over chemical accessibility of selected hydroxyl groups through the extent of hydration, allowing regioselective reactions, a major challenge in cellulose modification. The reactions mediated by surface-confined water are sustainable and largely outperform those occurring in organic solvents in terms of efficiency and environmental compatibility. Our results demonstrate the unexploited potential of water bound to cellulosic nanostructures in surface esterifications, which can be extended to a wide range of other nanoporous polymeric structures and reactions.

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Section: Control Of Chemical Accessibility and Effect On Bulk Propertiesmentioning

confidence: 80%

Section: Resultsmentioning

confidence: 99%

Unique reactivity of nanoporous cellulosic materials mediated by surface-confined water

et al. 2021

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“…Thereby, CNF with the same selectivity (C6) and largely similar chemical functionality (succinate vs.carboxylate) as the well-known TEMPO-CNF were obtained. The esterification was mediated via a reactive acylimidazole intermediate, [18][19][20] and can be applied directly to never-dried biomass, i.e., wet pulp fibers, commonly used for the preparation of typical CNF . [10,12,18] as it is an acyl transfer rather than a classical esterification mechanism.…”

Section: Resultsmentioning

confidence: 99%

“…This surface modification is introduced on the entire fibril surface, with very high selectivity towards the primary hydroxyl group of cellulose. [18][19][20] The method is mild and does not lead to dissolution nor influence the inherent physico-chemical properties such as crystallinity, and molar mass while preserving the morphology of the elementary, even at complete surface functionalization. Preserving such native properties are essential to maintain the excellent mechanical properties of cellulose.…”

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confidence: 99%

Assembling Native Elementary Cellulose Nanofibrils via a Dynamic and Spatially Confined Functionalization

Beaumont

Tardy²,

Reyes³

et al. 2021

Preprint

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Selective surface modification of bio-sourced colloids affords effective fractionation and functionalization of polysaccharide-based nanomaterials, as shown by the classic TEMPO-mediated oxidation. However, such route leads to changes of the native surface chemistry, affecting interparticle interactions and limiting the full exploitation of the supermaterial properties associated with such nanomaterial assemblies. Here we introduce a methodology to extract elementary cellulose fibrils by treatment of biomass with N-succinylimidazole, achieving spatially confined (92% regioselectivity towards primary C6-OH) and dynamic surface functionalization, as elucidated by nuclear magnetic resonance, infrared spectroscopy, and gel permeation chromatography. No polymer degradation or crosslinking nor changes in crystallinity occur under the mild conditions of the process yielding elementary fibrils. The structure of the fibrils was validated by cross-corelating solid-state NMR, chromatographic analysis, and atomic force microscopy imaging. We demonstrate the fully reversible nature of the dynamic modification, which offers a significant opportunity for the reconstitution of the interfaces back to the native states, chemically and structurally. Consequently, access to 3D structuring of native elementary cellulose I fibrils is made possible, reproducing the supramolecular features of the native cellulosic supermaterials. Overall, we propose the reversible and regioselective surface succinylation as a suitable route to overcome current limitations in the production of cellulose nanomaterials, which is required to unlock the full potential of cellulose as a sustainable building block.<br>

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“…Recently, also a wet esterification process for cellulose has been developed 205 yielding a surface-acetylated CNF. 262 It is expected that this protocol will be also applicable to other polysaccharides. Thiolation of a polysaccharide can be achieved by using a reaction of thiourea with halogenated polysaccharides ( Figure 4 H).…”

Section: Chemical Modificationmentioning

confidence: 99%

Hydrogel-Forming Algae Polysaccharides: From Seaweed to Biomedical Applications

et al. 2021

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With the increasing growth of the algae industry and the development of algae biorefinery, there is a growing need for high-value applications of algae-extracted biopolymers. The utilization of such biopolymers in the biomedical field can be considered as one of the most attractive applications but is challenging to implement. Historically, polysaccharides extracted from seaweed have been used for a long time in biomedical research, for example, agarose gels for electrophoresis and bacterial culture. To overcome the current challenges in polysaccharides and help further the development of high-added-value applications, an overview of the entire polysaccharide journey from seaweed to biomedical applications is needed. This encompasses algae culture, extraction, chemistry, characterization, processing, and an understanding of the interactions of soft matter with living organisms. In this review, we present algae polysaccharides that intrinsically form hydrogels: alginate, carrageenan, ulvan, starch, agarose, porphyran, and (nano)cellulose and classify these by their gelation mechanisms. The focus of this review further lays on the culture and extraction strategies to obtain pure polysaccharides, their structure-properties relationships, the current advances in chemical backbone modifications, and how these modifications can be used to tune the polysaccharide properties. The available techniques to characterize each organization scale of a polysaccharide hydrogel are presented, and the impact on their interactions with biological systems is discussed. Finally, a perspective of the anticipated development of the whole field and how the further utilization of hydrogel-forming polysaccharides extracted from algae can revolutionize the current algae industry are suggested.

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Wet esterification of never-dried cellulose: a simple process to surface-acetylated cellulose nanofibers

Abstract: Here we present a general concept of wet surface esterification of cellulose using acyl imidazoles, which enables direct acetylation of never-dried cellulose fibres in aqueous conditions. We hope that due...

Cited by 53 publications

References 37 publications

Unique reactivity of nanoporous cellulosic materials mediated by surface-confined water

Unique reactivity of nanoporous cellulosic materials mediated by surface-confined water

Assembling Native Elementary Cellulose Nanofibrils via a Dynamic and Spatially Confined Functionalization

Hydrogel-Forming Algae Polysaccharides: From Seaweed to Biomedical Applications

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