Swelling and dissolution kinetics of natural and man-made cellulose fibers in solvent power tuned ionic liquid

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ORIGINAL RESEARCH

Swelling and dissolution kinetics of natural and man-made cellulose fibers in solvent power tuned ionic liquid Feng Chen . Daisuke Sawada . Michael Hummel . Herbert Sixta . Tatiana Budtova

Received: 24 April 2020 / Accepted: 24 June 2020 Ó Springer Nature B.V. 2020

Abstract The kinetics of the dissolution and swelling of different cellulose fibers in the ionic liquid 1-ethyl-3-methylimidazolium acetate ([EMIM][OAc]) was studied by varying solvent power and temperature. Natural fiber, flax, and man-made fibers, Cordenka and Lyocell-type (Ioncell) were used with one Ioncell fiber containing lignin and hemicelluloses. Through the addition of water, the solvent power was modified from very good (neat ionic liquid), to moderate (with 5 wt% water) and weak (15 wt% water). The temperature was varied to correlate the fiber dissolution rate with the solvent viscosity. All

fibers were characterized by chemical composition, crystallinity, molecular weight distribution and dynamic vapor sorption. It was demonstrated that while the rate of fiber dissolution in neat ionic liquid depends on fiber accessibility and solvent viscosity, the water-induced decreased solvent power dominates the general fiber behavior. Flax appeared to be the most ‘‘sensitive’’ to the solvent power due to its hierarchical structure. The fastest dissolution or swelling was recorded for Ioncell and the slowest for Cordenka.

Supplementary information is available for this paper at https://doi.org/10.1007/s10570-020-03312-5. F. Chen  D. Sawada  M. Hummel  H. Sixta  T. Budtova Department of Bioproducts and Biosystems, School of Chemical Engineering, Aalto University, P.O. Box 16300, 00076 Helsinki, Finland T. Budtova (&) Center for Materials Forming-CEMEF, UMR CNRS 7635, MINES ParisTech, PSL Research University, CS 10207, 06904 Sophia Antipolis, France e-mail: [email protected]

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Cellulose

Graphic abstract

Keywords Cellulose fiber  Ionic liquid  Dissolution  Swelling  Accessibility

Introduction Cellulose is a fascinating biopolymer present on the Earth in almost inexhaustible quantity. It is a linear polymer built of anhydroglucose units linked by (1?4)-b glycosidic bonds, and until recently it was used mainly for making paper, textile fibers and films (Klemm et al. 2005; Ragauskas et al. 2006). Cellulose cannot be melt-processed (Chen et al. 2015) and thus its shaping requires dissolution (Gross and Chu 2010). During the past decades, new cellulose-based materials were developed involving complete or partial dissolution, for example, aerogels (Budtova 2019) and all-cellulose composites (Takashi et al. 2004). Several direct cellulose solvents are known, with LiCl/N,N-dimethylacetamide (DMAc) (McCormick et al. 1985), NaOH-based aqueous solutions (Budtova and Navard 2016), N-methylmorpholine N-oxide (NMMO) monohydrate (Fink et al. 2001) and ionic liquids (ILs) (Swatloski et al. 2002) being the most popular ones. Among these solvents, only NMMO

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monohydrat