Synthesis and application of functionalized ionic liquids-based imidazolium as solvent for cotton fibre cellulose dissolution

Cotton fibre dissolution has been investigated using ionic liquids having a functionalized imidazolium cation. Two ionic liquids, 3-butyric acid-1-methyl imidazolium chloride [HOOC4MIM][Cl] (IL-acid) and 3-N,N-diethyl-butyramide-1-methyl imidazolium chloride [(Et)(2)NOC4MIM][Cl] (IL-amide), were synthesized by passing both through the intermediate 1-(3-Ethoxycarbonyl-propyl)-1-methyl imidazolium bromide. Their chemical structures were then confirmed using NMR and FTIR. 5 wt% cotton fibers have been completely dissolved in both synthesized ionic liquids in 3 h at room temperature. The regenerated cellulose with water, as an anti-solvent, was characterized using XRD, FTIR, TGA, and degree of polymerization (DP) methods. The FTIR and XRD results showed that no other chemical reaction occurred by both synthesized ILs other than the breakage of hydrogen bonds during the dissolution and regeneration processes. In addition, the regenerated cellulose had a reduced crystallinity and a structural transition from cellulose I to cellulose II. TGA results confirmed the low crystallinity of regenerated cellulose by demonstrating its low thermal stability compared to cotton fibers. Furthermore, the DP of cotton fibers was reduced from 805 & PLUSMN; 15 to 737 & PLUSMN; 12 and 765 & PLUSMN; 10 after regeneration from IL-acid and IL-amide, respectively, confirming partial cellulose network degradation. The IL-acid has an oily appearance and a viscosity (44 & PLUSMN; 5 mPa.s at 25 & DEG;C), allowing it to dissolve 14.5 wt% cotton fibers at 25 & DEG;C, IL-amide can only dissolve 5 wt% in 5 h at 25 & DEG;C due to its viscous nature. These results imply that the produced ionic liquids can be considered as competitive solvents for dissolving cellulose.