Directed Discovery of Greener Cosolvents: New Cosolvents for Use in Ionic Liquid Based Organic Electrolyte Solutions for Cellulose Dissolution
2016
Gale, Ella | Wirawan, Remigius H. | Silveira, Rodrigo L. | Pereira, Caroline S. | Johns, Marcus A. | Skaf, Munir S. | Scott, Janet L.
Cellulose is an abundant, cheap, renewable, yet recalcitrant, material, which, if dissolved, may be formed into a wide range of materials, composites, and mixtures. Much attention has recently been focused on the use of mixtures of ionic liquids and some solvents (so-called organic electrolyte solutions, OESs) as efficient cellulose dissolution solvents, but many of the cosolvents used lack green credentials—a perennial problem where dipolar aprotic solvents are the solvents of choice. We present a rational approach, based on definition of ranges of solvent parameters gathered together in recently published databases, to find “greener” cosolvents for OES formation. Thus, γ-butyrolactone is identified as a suitable OES former for dissolution of microcrystalline cellulose and biobased γ-valerolactone as a marginally less efficient, but significantly safer, alternative. Comparison of cosolvent efficiency reveals that previous use of measures of mass, or concentration, of cellulose dissolved may have masked the similarities between 1-methylimidazole, dimethyl sulfoxide (DMSO), N,N-dimethylformamide, N-N′-dimethylimidazolidinone, N,N-dimethylacetamide, N-methylpyrrolidinone, and sulfolane (seldom considered), while comparison on a molar basis reveals that the molar volume of the solvent is an important factor. Reference-interaction site model (RISM) calculations for the DMSO/1-ethyl-3-methylimidazolium acetate OES suggest competition between DMSO and the acetate anion and preferential solvation of cellulose by the ionic liquid.
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