Cellulose is the most abundant, biopolymer on Earth. It has numerous applications in many industries and can be engineered into fibers, films, sponges, beads, and other cellulosic objects. Many of these applications require cellulose to be dissolved in a solvent. During the past decade, the dissolution of cellulose in ionic liquids (ILs) has been extensively studied. However, the mechanism of cellulose dissolution, especially the role of IL cation in the dissolution process, is not well understood. In this study, we performed a systematic study to understand the effect of substituent groups at the cation in imidazolium-based ILs on cellulose dissolution. We synthesized a series of imidazolium-based ILs with acetate as the common anion; 1-hepyl-3-methylimidazolium acetate ([C7C1im][OAc]), 1-(cyclohexylmethyl)-3-methylimidazolium acetate ([CyhmC1im][OAc]), 1-benzyl-3-methylimidazolium acetate ([BnzC1im][OAc]), 1,3-dibenzylimidazolium acetate ([(Bnz)2im][OAc]), and 1-(2-napthylmethyl)-3-methylimidazolium acetate ([NapmC1im][OAc]). In each dissolution experiment, 5% (w/w) ground cotton fiber was dissolved in the ILs below 100°C. The progress of the dissolution was monitored periodically with a polarized light microscope. We discovered that [BnzC1im][OAc] dissolved cotton cellulose more efficiently than the other four ILs. For the five ILs that were investigated, we find that the effect of the cation can be rationalized on the basis of both the size and shape of the cation. In addition to the dissolution, the cellulose was regenerated, and characterized by Fourier transform infrared spectroscopy and scanning electron microscopy.

Cellulose dissolution in imidazolium-based ionic liquids: Effect of size and shape of cations

2019 Spring National Meeting

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