Mixtures of ionic liquids as more efficient media for cellulose dissolution

Area of Science:

• Materials Science
• Green Chemistry
• Polymer Chemistry

Background:

• Cellulose dissolution is crucial for its applications.
• Ionic liquids offer potential for cellulose dissolution.
• Optimizing ionic liquid systems for cellulose solubility is an ongoing challenge.

Purpose of the Study:

• To investigate cellulose dissolution in ionic liquid mixtures.
• To compare the efficacy of different ionic liquid mixtures and co-solvents.
• To characterize the physical properties of the systems and the regenerated cellulose.

Main Methods:

• Testing cellulose dissolution in [C2mim]Cl/[C2mim][OAc] and [C2mim]Cl/C4mim]Cl mixtures at varying temperatures.
• Evaluating the effect of dimethylsulfoxide (DMSO) as a co-solvent.
• Measuring physical properties (density, surface tension, viscosity) and characterizing regenerated cellulose (pXRD, TGA, optical microscopy).

Main Results:

• The [C2mim]Cl+[C2mim][OAc] mixture dissolved up to 40g cellulose/100g solvent at 373K.
• Addition of 50mol% DMSO increased cellulose dissolution to 43g/100g solvent, a new record.
• Dissolved cellulose was easily regenerated into cellulose II, confirmed by pXRD.

Conclusions:

• Ionic liquid mixtures, particularly with DMSO co-solvent, significantly enhance cellulose dissolution.
• The study reports the highest cellulose dissolution in ionic liquid media to date.
• The dissolution-regeneration process effectively converts cellulose I to cellulose II.