Interactions of Ionic Liquids with Polysaccharides – 2: Cellulose

Abstract

Some general comments about ionic liquids (ILs) and carbohydrates are given. The main scope of the review is to discuss the present state of the art of chemical modification of cellulose applying IL as reaction media considering own research results. ILs, namely 1‐butyl‐3‐methylimidazolium chloride (BMIMCl), 1‐ethyl‐ 3‐methylimidazolium chloride (EMIMCl), 1‐butyl‐2,3‐dimethylimidazolium chloride (BDMIMCl), 1‐allyl‐2,3‐dimethylimidazolium bromide (ADMIMBr) and 1‐ethyl‐3‐ methylimidazolium acetate (EMIMAc) are solvents for cellulose (even for high molecular bacterial synthesized cellulose) and can easily be applied as reaction media for cellulose modification. We investigated the homogeneous acylation, carbanilation and silylation of the biopolymer cellulose. Under mild conditions and within short reaction time at low temperature (65 °C to 80 °C) and low excess of reagent, various cellulose esters and carbanilates, dendronized cellulose and trimethylsilyl cellulose were obtained. The DS of the cellulose derivatives can be controlled by varying the reaction time, reaction temperature and the IL used as reaction medium.

Homogenous esterification of cellulose pulp in [DBNH][OAc]

“…For instance, the ability to dissolve cellulose is often dependent on the basicity of the IL (Fukaya et al 2006(Fukaya et al , 2008King et al 2012;Parviainen et al 2013), but there are exceptions, e.g., tetraalkylphosphonium salts Holding et al 2014), which are basic but require a dipolar aprotic co-solvent to dissolve cellulose. In previous literature, the use of imidazolium based ILs, with alkyl substituents (ethyl, methyl, and allyl) and chloride, bromide or acetate anions, typifies most publications on cellulose dissolving ILs (Heinze et al 2008;Swatloski et al 2002). In regard to developing commercial processes, the potential environmental impacts of ILs are also of concern.…”

Effect of methylimidazole on cellulose/ionic liquid solutions and regenerated material therefrom

“…The ILs that are able to dissolve cellulose include several classes of cations and a multitude of anions. Some of the most common cations are imidazolium, pyridinium, ammonium, and phosphonium derivatives [16]. Although imidazolium-based ILs are known to form covalent bonds with cellulose in some cases [17,18], they are still among the most used in academic research on ILs and cellulose and still highly interesting for biomass processing [19].…”

Co-Solvent Facilitated in situ Esterification of Cellulose in 1-Ethyl-3-Methylimidazolium Acetate

“…The co-solvent MIM is known to catalyze some reactions. For the trimethylsilylation of cellulose in imidazolium based ionic liquids, it was found that the amount of MIM, which is a starting molecule for the synthesis of the solvent, had an impact on the degree of substitution in the final product (Kohler et al 2008). Furthermore, in DMAc/LiCl, the esterification of cellulose by carboxylic acid anhydrides is efficiently catalyzed by imidazole (Nawaz et al 2013).…”

“…Second, in the specific case of using [EMIm][OAc] as a solvent, the addition of large amounts of a co-solvent reduces the amount of acetate ions available for cellulose acetylation as the side reaction. Third, in some cases, secondary solvents are actually required for a successful reaction to take place at all (Kohler et al 2008).…”

“…DMSO is a well-known cosolvent for cellulose and has been used in homogeneous derivatization, e.g., in combination with tetrabutylammonium fluoride (Ass et al 2004;Ramos et al 2005) or ILs (Liu et al 2006). The co-solvent MIM has many interesting properties and has been reported to act as a catalyst in cellulose chemistry (Kohler et al 2008).…”