Superior cellulose-protective effects of cosolvent during enhanced dissolution in imidazolium ionic liquid

Abstract

Abstract To improve the solubility of cellulose at lower temperatures, several polar organic solvents were examined as cosolvents in imidazolium ionic liquid (IL). All tested cosolvents increased the solubilization efficiency of ILs at lower temperatures. Among these, N-methylimidazole, N-methyl-2-pyrrolidone, and dimethyl sulfoxide (DMSO) were notably efficient; in case of Avicel the solubility was increased, with 12–15% cellulose dissolution in 1-allyl-3-methylimidazolium chloride ([Amim]Cl) at 30°C. IR spectra of the regenerated celluloses from IL/cosolvent systems showed characteristic features of cellulose II and/or amorphous cellulose. Thermogravimetric analyses showed significantly higher thermal stability of regenerated cellulose from [Amim]Cl/DMSO compared with that without DMSO. Moreover, dimethylacetamide (DMAc) increased the solubility of filter paper pulp in 1-ethyl-3-methylimidazolium acetate ([Emim]OAc), with 12% pulp dissolution at 30°C. No decrease in the degree of polymerization (DP) of cellulose was observed with [Emim]OAc/DMAc, whereas 8–9% DP decrease was observed with [Emim]OAc, even at 30°C. These results indicate that some cosolvents including DMSO and DMAc increase solubilization efficiency and have superior cellulose-protective effects during enhanced dissolution in ILs.