Tailored Media for Homogeneous Cellulose Chemistry: Ionic Liquid/Co-Solvent Mixtures

• Published in: Macromolecular materials and engineering Vol. 296; no. 6; pp. 483 - 493
• Main Authors: Gericke, Martin, Liebert, Tim, Seoud, Omar A. El, Heinze, Thomas
• Format: Journal Article
• Language: English
• Published: Weinheim WILEY-VCH Verlag 16.06.2011; WILEY‐VCH Verlag
• Subjects: Basicity; Cellulose; co-solvents; Cobalt; Guidelines; Ionic liquids; miscibility; Polarity; solvatochromic parameters; Solvents; Viscosity
• ISSN: 1438-7492; 1439-2054; 1439-2054
• DOI: 10.1002/mame.201000330

Co‐solvents can minimize two of the major problems associated with the use of ionic liquids (ILs) as solvents for homogeneous derivatization of cellulose: high viscosity and limited miscibility with non‐polar reagents or reaction products. Thus, the effects of 18 solvents and 3 binary solvent mixtures on cellulose solutions in three ILs were systematically studied with respect to the solution phase behavior. The applicable limits of these mixtures were evaluated and general guidelines for the use of co‐solvents in cellulose chemistry could be advanced: Appropriate co‐solvents should have $E_{{\rm T}}^{{\rm N}} $ values (normalized empirical polarity) > 0.3, very low “acidity” (α < 0.5), and relatively high “basicity” (β ≥ 0.4). Moreover, novel promising co‐solvents and binary co‐solvent mixtures were identified. Ionic liquids are commercially attractive solvents for shaping and chemical modification of cellulose but their application is strongly restricted because of their exceptionaly high viscosity and poor miscibility with hydrophobic reagents. In this comprehensive study general guidelines for the utilization of co‐solvents in cellulose chemistry are evolved that omit these major drawbacks.