Microstructures of cellulose coagulated in water and alcohols from 1-ethyl-3-methylimidazolium acetate: contrasting coagulation mechanisms

Research output: Contribution to journalArticle

Abstract

Abstract: Coagulation of cellulose solutions is a process whereby many useful materials with variable microstructures and properties can be produced. This study investigates the complexity of the phase separation that generates the structural heterogeneity of such materials. The ionic liquid, 1-ethyl-3-methylimidazolium acetate ([C2mim][OAc]), and a co-solvent, dimethylsulfoxide (DMSO), are used to dissolve microcrystalline cellulose in concentrations from 5 to 25 wt%. The solutions are coagulated in water or 2-propanol (2PrOH). The coagulated material is then washed and solvent exchanged (water → 2PrOH → butanone → cyclohexane) in order to preserve the generated microstructures upon subsequent drying before analysis. Sweep electron microscopy images of 50 k magnification reveal open-pore fibrillar structures. The crystalline constituents of those fibrils are estimated using wide-angle X-ray spectroscopy and specific surface area data. It is found that the crystalline order or crystallite size is reduced by an increase in cellulose concentration, by the use of the co-solvent DMSO, or by the use of 2PrOH instead of water as the coagulant. Because previous theories cannot explain these trends, an alternative explanation is presented here focused on solid–liquid versus liquid–liquid phase separations. Graphical abstract: [Figure not available: see fulltext.].

Details

Authors
  • Artur Hedlund
  • Tobias Köhnke
  • Joel Hagman
  • Ulf Olsson
  • Hans Theliander
Organisations
External organisations
  • Chalmers University of Technology
  • Swerea IVF
  • KTH Royal Institute of Technology
Research areas and keywords

Subject classification (UKÄ) – MANDATORY

  • Paper, Pulp and Fiber Technology
  • Materials Chemistry

Keywords

  • Cellulose, Co-solvent, Ionic liquid, Microstructure, Non-solvent, Regeneration
Original languageEnglish
Pages (from-to)1545-1563
JournalCellulose
Volume26
Issue number3
Early online date2018 Dec 15
Publication statusPublished - 2019
Publication categoryResearch
Peer-reviewedYes