Preparation of Nanocellulose Using Ionic Liquids: 1-Propyl-3-Methylimidazolium Chloride and 1-Ethyl-3-Methylimidazolium Chloride

Abstract

Cellulose nanocrystals were prepared using ionic liquids (ILs), 1-ethyl-3-methylimidazolium chloride [EMIM][Cl] and 1-propyl-3-methylimidazolium chloride [PMIM][Cl], from microcrystalline cellulose. The resultant samples were characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), dynamic light scattering (DLS), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). The XRD results showed that nanocellulose obtained by treatment with both ILs preserved basic cellulose I structure, but crystallinity index of samples (except for Sigmacell treated with [EMIM][Cl]) was lower in comparison to the starting microcrystalline cellulose. The DLS results indicated noticeably smaller particle sizes of prepared cellulose for material treated with [PMIM][Cl] compared to cellulose samples hydrolyzed with [EMIM][Cl], which were prone to agglomeration. The obtained nanocellulose had a rod-like structure that was confirmed by electron microscopy analyses. Moreover, the results described in this paper indicate that cation type of ILs influences particle size and morphology of cellulose after treatment with ionic liquids.

Nanocellulose Production Using Ionic Liquids with Enzymatic Pretreatment

“…The cellulose material after treatment with ionic liquids had a more regular and spherical structure than cellulose hydrolyzed with the Trichoderma reesei enzyme. The spherical structure of obtained nanocellulose is in contrast to the results of other research, where nanocelluloses produced by hydrolysis with an ionic liquid had needle-or rod-like morphologies [23,44,47,70].…”

“…The reaction of enzyme-pretreated cellulose with AmimCl caused decreases of the crystallinity index by about 60% for Avicel cellulose and 48% for Whatman cellulose compared to the enzyme-pretreated material. Such reductions in the degree of crystallinity for cellulose treated with ionic liquids were previously reported by other authors [44,70,76]. The degree of crystallinity of eucalyptus pulp amounting to 70% was reduced to 36% by treatment with an ionic liquid, namely BmimCl [76].…”

“…The values of the crystallinity index indicated that enzymatic hydrolysis affected the degree of crystallinity of the raw cellulose material. The crystallinity index values for enzyme-pretreated cellulose were 60% for Avicel and 63% for Whatman types compared to 61% and 75% for untreated raw Avicel and Whatman cellulose, respectively [44,77]. However, significant changes in the degree of crystallinity were noted for the cellulose samples obtained after hydrolysis with ionic liquids.…”

“…Ionic liquids, often referred to as green solvents, have been used in the production of nanocellulose [42][43][44][45]. Ionic liquids (ILs) are generally defined as salts that melt below 100 • C and are completely composed of ions.…”

A Concise Review on the Physicochemical Properties of Biopolymer Blends Prepared in Ionic Liquids

“…1-Ethyl-3-methylimidazolium chloride can be synthesized through alkylation reaction as well by reacting N -methylimidazole with 1-chloroethane in acetonitrile [ 57 ]. Table 3 shows the 1-ethyl-3-methylimidazolium-based ionic liquids with different counter anions utilized for dissolution of biopolymers.…”