Binary mixtures of ionic liquids-DMSO as solvents for the dissolution and derivatization of cellulose: Effects of alkyl and alkoxy side chains

Daniela C Ferreira; Mayara L Oliveira; Thais A Bioni; Haq Nawaz; Alistair W T King; Ilkka Kilpeläinen; Michael Hummel; Herbert Sixta; Omar A El Seoud

doi:10.1016/j.carbpol.2019.02.024

Binary mixtures of ionic liquids-DMSO as solvents for the dissolution and derivatization of cellulose: Effects of alkyl and alkoxy side chains

Carbohydr Polym. 2019 May 15:212:206-214. doi: 10.1016/j.carbpol.2019.02.024. Epub 2019 Feb 16.

Authors

Daniela C Ferreira¹, Mayara L Oliveira², Thais A Bioni², Haq Nawaz², Alistair W T King³, Ilkka Kilpeläinen³, Michael Hummel⁴, Herbert Sixta⁵, Omar A El Seoud⁶

Affiliations

¹ Institute of Chemistry, The University of São Paulo, Prof. Lineu Prestes Av., 748, 05508-000, São Paulo, SP, Brazil; Institute for Technological Research from State of São Paulo, Prof. Almeida Prado Av., 532, 05508-901, São Paulo, SP, Brazil.
² Institute of Chemistry, The University of São Paulo, Prof. Lineu Prestes Av., 748, 05508-000, São Paulo, SP, Brazil.
³ Department of Chemistry, University of Helsinki A.I. Virtasen Aukio 1, 00014, P.O. Box 55, Helsinki, Finland.
⁴ Department of Bioproducts and Biosystems, School of Chemical Engineering, Aalto University, P.O. Box 16300, FI-00076, Aalto, Finland.
⁵ Department of Bioproducts and Biosystems, School of Chemical Engineering, Aalto University, P.O. Box 16300, FI-00076, Aalto, Finland. Electronic address: herbert.sixta@aalto.fi.
⁶ Institute of Chemistry, The University of São Paulo, Prof. Lineu Prestes Av., 748, 05508-000, São Paulo, SP, Brazil. Electronic address: elseoud@usp.br.

PMID: 30832848
DOI: 10.1016/j.carbpol.2019.02.024

Abstract

The efficiency of mixtures of ionic liquids (ILs) and molecular solvents in cellulose dissolution and derivatization depends on the structures of both components. We investigated the ILs 1-(1-butyl)-3-methylimidazolium acetate (C₄MeImAc) and 1-(2-methoxyethyl)-3-methylimidazolium acetate (C₃OMeImAc) and their solutions in dimethyl sulfoxide, DMSO, to assess the effect of presence of an ether linkage in the IL side-chain. Surprisingly, C₄MeImAc-DMSO was more efficient than C₃OMeImAc-DMSO for the dissolution and acylation of cellulose. We investigated both solvents using rheology, NMR spectroscopy, and solvatochromism. Mixtures of C₃OMeImAc-DMSO are more viscous, less basic, and form weaker hydrogen bonds with cellobiose than C₄MeImAc-DMSO. We attribute the lower efficiency of C₃OMeImAc to "deactivation" of the ether oxygen and C2H of the imidazolium ring due to intramolecular hydrogen bonding. Using the corresponding ILs with C2CH₃ instead of C2H, namely, 1-butyl-2,3-dimethylimidazolium acetate (C₄Me₂ImAc) and 1-(2-methoxyethyl)-2,3-dimethylimidazolium acetate (C₃OMe₂ImAc) increased the concentration of dissolved cellulose; without noticeable effect on biopolymer reactivity.

Keywords: Biopolymer derivatization; Cellulose dissolution; Cellulose esters; Ionic liquid-DMSO; Solvatochromism.