University of Oulu

Sirviö, J.A., Ukkola, J. & Liimatainen, H. Cellulose (2019) 26: 2303.

Direct sulfation of cellulose fibers using a reactive deep eutectic solvent to produce highly charged cellulose nanofibers

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Author: Sirviö, Juho Antti1; Ukkola, Jonne1; Liimatainen, Henrikki1
Organizations: 1Fibre and Particle Engineering Research Unit, University of Oulu, P.O. Box 4300, 90014 Oulu, Finland
Format: article
Version: published version
Access: open
Online Access: PDF Full Text (PDF, 0.9 MB)
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Language: English
Published: Springer Nature, 2019
Publish Date: 2019-02-26


Wood cellulose pulp was sulfated using a reactive deep eutectic solvent (DES). DES was prepared by heating sulfamic acid and urea together at 80 °C at a molar ratio of 1:4, 1:3, or 1:2. Sulfation of cellulose was performed by mixing dry cellulose fibers with DES at 80 °C, followed by heating at 150 °C for half an hour. Anionic charge as high as 3 mmol/g (degree of substitution of 0.68) was obtained with this simple chemical modification of cellulose at an elevated temperature using DES both as reaction media and reagent without any external solvent. The decrease in the urea content of DES improved the sulfation efficiency. In addition, the presence of urea led to the carbamation of cellulose to some extent. Cellulose sulfate (charge of 2.40 mmol/g) became a gel-like material in water, and after passing once through a microfluidizator, a highly transparent nanocellulose gel (transmittance of 0.1% solution at a visible light range was over 95%) was obtained. Sulfated cellulose nanofibers (SCNFs) exhibited a width of around 4 nm with a minor presence of elemental fibril aggregates (containing five or less elemental fibrils). SCNFs with high aspect ratio can have a potential end-use as a rheology modifier because of their high viscosity even at low concentrations or act as reinforcing additives.

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Series: Cellulose
ISSN: 0969-0239
ISSN-E: 1572-882X
ISSN-L: 0969-0239
Volume: 26
Issue: 4
Pages: 2303 - 2316
DOI: 10.1007/s10570-019-02257-8
Type of Publication: A1 Journal article – refereed
Field of Science: 221 Nanotechnology
Funding: Open access funding provided by University of Oulu including Oulu University Hospital.
Copyright information: © The Author(s) 2019. This article is distributed under the terms of the Creative Commons Attribution 4.0 International License (, which permits unrestricted use, distribution, and reproduction in any medium, provided you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made.