Cellulose In Ionic Liquids Research Articles

Molecular insight into the dissolution-degradation process of cellulose bunch in ionic liquids

Ionic liquids (ILs) as green solvents have been utilized in dissolving cellulose and fabricating regenerated cellulose fibers. Imidazolium-based ILs with acetate or phosphate anions present advantage, due to the low viscosity and melting point, as well as its excellent ability to form hydrogen bonds (H-bonds) with the hydroxyl groups of cellulose chains. In this work, the microscopic dissolution processes of a cellulose bunch in four ILs were reproduced via molecular dynamics (MD) simulations. The cellulose bunch dissolution capabilities of these four ILs are [Emim][OAc] > [Emim][DMP] > [Emim][DEP] > [Bmim][DMP], as verified through in-situ polarized optical microscope. It is important to note that cellulose may degrade in some ILs during dissolution, affecting the performance of regenerated cellulose, while the underlying mechanism is unclear, and the strength of H-bonds formed between ILs and cellulose chains can reflect their degradation strength Combined with density functional theory (DFT) calculations, the H-bonds formed between different anions and cellulose hydroxyl groups were analyzed in depth and the order of H-bond strength is [OAc]− > [DEP]− > [DMP]−, which is different from the dissolution order of cellulose bunch in [Emim][DEP] and [Emim][DMP]. Further analysis revealed that the difference in diffusion coefficients leads to faster dissolution of cellulose in [Emim][DMP]. This study elucidates the dissolution and degradation processes of cellulose in ILs at the molecular level, offering theoretical insights crucial for the development of novel ILs that are efficient in the process of cellulose spinning.

Molecular dynamics study on effects of the synergistic effect of anions and cations on the dissolution of cellulose in ionic liquids

This work systematically explores the interaction between cellulose and various ionic liquids (ILs) formed by the pairing of glycine cations with diverse anions. Results show that the interaction of anions with cellulose decreases in the order of [CH3COO]− > [Im]− > [SCN]− > Cl− > [PF6]−, differing from imidazole-based ionic liquids. The synergistic effect of anions and cations is crucial for cellulose dissolution. Moreover, the electronegativity of anions can enhance their interaction with cellulose. Short alkyl chains (n = 1, 3, 5) reduce hydrogen bonding due to steric hindrance, while longer chains (n = 9) promote diffusion and hydrogen bond formation. The introduction of electron-withdrawing groups to anions weakens their interaction with cellulose, while marginally strengthening the association between cations and cellulose. Overall, a delicate balance among anion-cation-cellulose interactions is essential for effective cellulose dissolution. The obtained results are anticipated to be of significant importance in the rational design of innovative amino acid-based ionic liquids, aiming to achieve efficient cellulose dissolution.

Swelling and dissolution behaviors of cellulose in phosphate-based ionic liquids-H2O binary systems: In-situ observation and molecular dynamics simulation

Swelling and dissolution of cellulose in ionic liquids (ILs) as the pretreatment processes are key steps for the high-value conversion and utilization of cellulose. However, the molar ratio of H2O to ILs has a significant effect on the swelling and dissolution of cellulose, and its molecular-scale mechanism is still unclear, which limits screening out the suitable ILs and recovery of ILs from coagulation bath in the spinning process. Herein, three phosphate-based ILs were chosen to couple with water as solvents for swelling and dissolution of cellulose by combining in-situ observation and molecular dynamics (MD) simulation. The results show that the redissolution time of swollen cellulose is greatly reduced, especially [Emim]DEP-H2O has the best swelling and dissolution performance for cellulose due to its high β value and low viscosity. Meanwhile, when the molar ratio of IL to H2O was more than 1: 1, the IL-H2O system still has the ability to dissolve cellulose. While with the molar ratio further decreased, cellulose was no longer dissolved and began to swell, and the fiber diameter obtained the maximum swelling rate with 40.1% at a molar ratio of 1: 3. Moreover, MD simulation was used to calculate the interaction between IL/water/cellulose, which further illustrated that the combination of IL with water molecular has a significant influence on the behavior of cellulose in IL-H2O systems at the molecular scale. Thus, the potential swelling and dissolution mechanism of cellulose in ILs-H2O binary systems was proposed based on experimental and simulation results. Furthermore, the characterization results of swollen cellulose indicate that the crystal structure and degree of polymerization (DP) were almost unchanged, but the specific surface area and pore size increased significantly, and the thermal stability and heat absorption were decreased, all the results prove that the swelling process increased the accessibility of cellulose and benefited to the subsequent dissolution. Consequently, preferable swelling and dissolving parameters of experiments and simulations will provide a new idea for the selection of suitable ILs and the recovery of ILs from a coagulation bath in the dry-wet spinning process.

H-ZSM-5/GO Composites as a Catalyst for the Hydrolysis of Cellulose

Abstract: H-ZSM-5/GO composites were prepared for the catalytic hydrolysis of cellulose in ionic liquids of 1-butyl-3-methylimidazole chloride salt to obtain sugars. The materials catalyzed the hydrolysis of cellulose to produce total reducing sugar (TRS), super to ZSM-5 or graphene oxide (GO). The results suggested that the acidic sites of both materials and the mesopores of the composites enhanced the catalytic performance. With the optimized reaction conditions (e.g., ratio of catalyst to cellulose, temperature, reaction time), 87.8% yield of TRS was obtained.

Morphology and Lamellar Twisting of Spherulites in Cellulose–Ionic Liquid: Effect of Molecular Weight and Temperature

Morphology and Lamellar Twisting of Spherulites in Cellulose–Ionic Liquid: Effect of Molecular Weight and Temperature

Homogeneous Hydrophobic Modification of Hydroxyethyl Cellulose in Ionic Liquids

Homogeneous Hydrophobic Modification of Hydroxyethyl Cellulose in Ionic Liquids

Understanding leaching of amylopectin from cellulose/amylopectin/[Bmim][Cl] blends during regeneration from water and aqueous ethanol using molecular dynamic simulations

The difference in amylopectin leaching from cellulose/amylopectin/1-butyl-3-methylimidazolium chloride ([Bmim][Cl]) blends during regeneration in water and aqueous ethanol has been observed in experimental studies. To fully understand the above phenomenon, molecular dynamic simulation was adopted to illustrate the regeneration mechanism after dissolution to understand interactions responsible for the elution/leaching of amylopectin starch. Molecular dynamics (MD) simulations reveal that amylopectin dissolution in [Bmim][Cl] is similar to cellulose in ionic liquids (ILs). Strong hydroxyl-Cl- hydrogen bonding drives dissolution, with [Bmim]+ ions playing a stabilizing role through van der Waals interactions. Amylopectin regeneration in water and aqueous ethanol occurs through the initial disruption of weak hydroxyl-Cl- bridging bonds followed by the disruption of strong non-bridging hydrogen bonds. The water network intercalates amylopectin chains, forming a few “short-lived” interchain HBs. This leaves a very weak electrostatic interaction as the dominant intermolecular interaction between water-regenerated amylopectin chains. Water solvates and elutes low molecular weight amylopectin oligomers, with only 47.29 % amylopectin retained in the blend. In contrast, ethanol-water hydrophobic-hydrogen interactions disrupt the water network, create an ethanol-rich environment, shorten the intermolecular distance between chains, decrease diffusivity, increase hydrogen bonding lifetime between amylopectin, and regenerate amylopectin in aqueous ethanol. The regenerated amylopectin chains interact through improved but weak electrostatic interaction. Improved interaction between chains limits the erosion of low-molecular-weight amylopectin from films retaining 83.11 % amylopectin, approximately two times that in water. At a molecular level, we established that a very weak electrostatic interaction among amylopectin is responsible for leaching in water during regeneration. Ethanol enhances electrostatic interaction among amylopectin chains to limit amylopectin leaching in aqueous ethanol. These observations could apply to other polysaccharide blended materials prepared by the dissolution-regeneration method.

Development of cellulose films by means of the Ioncell® technology, as an alternative to commercial films

In recent years, the search for alternatives to petroleum derived products, such as plastic films, has become a priority due to the growing depletion of fossil reserves and the pollution of water resources by microplastics, microscopically small plastic particles which are harmful to ocean and aquatic life. Cellulose-based films, e.g., cellophane and cuprophane, have been on the market for almost a century. Despite being a more ecological option compared to plastic films, the manufacture of these cellulose films involves high production costs and the use of harmful chemicals. As an alternative, a sustainable and eco-friendly process based on the Lyocell-type Ioncell® technology is presented to produce cellulose films. Regenerated cellulose films are created by continuous extrusion via dry-jet wet spinning of an ionic liquid–cellulose solutions. The influence of the polymer concentration (8–13 wt%) and processing temperature (50–100 °C) on the properties of the films were studied by the determination of the thickness, mechanical properties, physical appearance, morphology, chemical composition, and hydrophobicity. The obtained films are thin (12–21 μm), transparent (transmittance = 91%) and of homogeneous structure. Moreover, they exhibit excellent mechanical properties: stress values up to 210 MPa and elongations up to 19% in machine (longitudinal) direction. These values clearly outperform commercial cellophane, which presents stress values of 125 MPa and elongations of 22%. The films presented herein hold great potential to become an eco-friendly and sustainable option to commercial films.

In situ saccharification of metal-containing ionic liquid pretreated (ligno)cellulose via alginate encapsulated cellulase@functionalized ZIF-8

The present work aimed to develop mixed-metal salts (MMs) assisted ionic liquid (IL) pretreatment for efficient in situ saccharification of (ligno)cellulose. To accommodate MMs-IL involved in situ saccharification, a novel immobilized cellulase based on amine-functionalized ZIF-8 and calcium alginate beads (Ce@ZIF-8-A/CA) was established. XRD, FT-IR and SEM were employed to characterize the immobilization carrier and immobilized cellulase. Compared to free cellulase, Ce@ZIF-8-A/CA showed enhanced tolerance to IL, MMs and temperature. Ce@ZIF-8-A/CA preserved more than 80% of original activity at a wide temperature range (40–70 °C) in 30% 1-butyl-3-methylpyridinium chloride ([BMPy]Cl), and retained 73.0% of initial activity in 1% MMs (FeCl3/LiCl) assisted 30% [BMPy]Cl. After pretreatment with MMs assisted [BMPy]Cl, 40%-60% (ligno)cellulose was decomposed into soluble lower-molecular-weight fragments without regeneration of cellulose after adding buffer. After in situ saccharification of pretreated slurries with Ce@ZIF-8-A/CA, total reducing sugars yields of 84.7% and 71.3% from cellulose and bagasse were obtained during 12 h, saving at least 12 h compared to traditional enzymatic in situ saccharification of (ligno)cellulose in IL.

Eucalyptus bleached kraft pulp-ionic liquid inks for 3D printing of ionogels and hydrogels

3D printing has been recently recognized as one of the most promising technologies due to the multiple options to fabricate cost-effective and customizable objects. However, the necessity to substitute fossil fuels as raw materials is increasing the research on bio-based inks with recyclable and eco-friendly properties. In this work, we formulated inks for the 3D printing of ionogels and hydrogels with bleached kraft pulp dissolved in [Emim][DMP] at different concentrations (1–4 wt%). We explored each ink's rheological properties and printability and compared the printability parameters with a commercial ink. The rheological results showed that the 3 % and 4 % cellulose-ionic liquid inks exhibited the best properties. Both had values of damping factor between 0.4 and 0.7 and values of yield stress between 1900 and 2500 Pa. Analyzing the printability, the 4 wt% ink was selected as the most promising because the printed ionogels and the hydrogels had the best print resolution and fidelity, similar to the reference ink. After printing, ionogels and hydrogels had values of the elastic modulus (G′) between 103 and 104 Pa, and the ionogels are recyclables. Altogether, these 3D printed cellulose ionogels and hydrogels may have an opportunity in the electrochemical and medical fields, respectively.

Influence of hydrostatic pressure during gelation on physicochemical properties of cellulose hydrogels prepared from ionic liquid/DMSO solution

Various studies have been conducted on the effect of gelation temperature on the physicochemical properties of hydrogels; however, the effect of hydrostatic pressure on these properties is yet to be investigated. In this study, cellulose hydrogels were prepared by dissolving cellulose in 60 wt% 1-butyl-3-methylimidazolium acetate/dimethyl sulfoxide (DMSO) and gelating the resultant solution by displacing it with water at hydrostatic pressures ranging from 0.1 to 250 MPa. The relationship between the hydrostatic pressure during gelation and physicochemical properties of the prepared cellulose hydrogels (shrinkage rate, water content, mechanical strength, and crystallinity) was thoroughly investigated. The results revealed that with the increase in the hydrostatic pressure, the water content of the cellulose hydrogels decreased and the cellulose hydrogels became denser. In contrast, the crystallinity (structure and orientation within the cellulose bundles that form the backbone of the cellulose hydrogels) and compressive modulus did not exhibit hydrostatic pressure dependence. Furthermore, by conducting molecular dynamics simulations of the cellulose/ionic liquid/water system under ambient and hydrostatic pressure (150 MPa and 250 MPa, respectively), the cellulose–ionic liquid, cellulose–DMSO, and cellulose–water radial distribution functions and coordination numbers were investigated to elucidate the effect of the hydrostatic pressure during gelation on the gel physicochemical properties from a molecular theoretical perspective. It was found that with increasing pressure, the water and DMSO coordinated around the cellulose both increased while the ionic liquid decreased. Thus, it was concluded that this decrease in the coordination number of ionic liquids to cellulose at higher pressure promotes aggregation between the cellulose bundles that form the backbone of cellulose hydrogels. This results in a decrease in the water content and an increase in the mechanical strength of the cellulose hydrogel. These results provide deep insight into the dependence of gel physicochemical properties on hydrostatic pressure during gelation and a platform to expand these applications using a convenient and environmentally friendly process.

Dehydrogenative silylation of cellulose in ionic liquid

A new homogenous silylation method of cellulose is developed by mixing it with monohydrosilane in an ionic liquid.

(Invited, Digital Presentation) From Textile Waste to Cellulose Aerogel Beads Using Ionic Liquid

A huge amount of waste textile is produced every year, and the majority is either burned, or buried in landfills, or downcycled. We propose making high added-value materials, aerogels, from textile waste, using ionic liquids. Aerogels are light-weight and nanostructured porous materials with high specific surface area. Depending on the type of textile, we use ionic liquid either to completely dissolve it (case of rayon or viscose), or to selectively dissolve cellulose (case of polycotton). Cellulose aerogels were made in the form of beads by prilling via dissolution in ionic liquid, coagulation and drying with supercritical CO2. Reference cellulose aerogel beads were made from microcrystalline cellulose to compare with textile-based aerogels.The rheological properties of cellulose-ionic liquid solutions were studied to select the processing conditions. Aerogel beads of the size from 0.5 to 1.5 mm with excellent circularity were obtained. Cellulose-based aerogel beads from textile and from microcrystalline cellulose have density around 0.1 g/cm3, porosity around 90% and high specific surface area, around 300 m²/g. Cytotoxicity tests showed that these aerogels may potentially be used for life science applications.AcknowledgementsWe are grateful to Institut Carnot MINES for the financial support of this work, Julien Jaxel (PERSEE) for the drying with supercritical CO2, Antoine Perron (GALA – RAPSODEE) for the prilling and Suzanne Jacomet (CEMEF) for the help in SEM pictures.

Hydrothermal reaction of cellulose in ionic liquid catalyzed by Er(OTf)3

This research explores the potential of ionic liquid to improve lactic acid yield of the hydrothermal reaction of cellulose. The research premise was that ionic liquid dissolved cellulose and water into liquid phase, which would facilitate the formation of glucose and lactic acid using water-tolerant catalyst Erbium (III) trifluoromethanesulfonate (Er(OTf)3). Contrary to the research premise, the experiment revealed that dissolving cellulose in ionic liquid prior to hydrothermal reaction lowered lactic acid yield while increasing hydroxymethylfurfural (HMF) yield. The phenomenon could be attributed to dissociation of water and ionic liquid to give hydronium ion and chloride ion, which subsequently formed hydrochloric acid (HCl). HCl catalyzed cellulose into HMF, in addition to lactic acid. Pressure and pressurized gas had minimal impact on the yield of lactic acid, while the hydrothermal reaction was affected by type of cation and anion of ionic liquid. The highest lactic acid yield of 54.26% was achieved by using 1-butyl-3 methylimidazolium chloride ionic liquid, with 190 °C, 30-min, 10 bar CO2 initial pressure, and Er(OTf)3 50 wt% cellulose. Meanwhile, the highest HMF yield of 66.06% was realized with 1-butyl-3-methylimidazolium hydrogen sulfate in the absence of Er(OTf)3.

Cellulose@PO3H: As an Efficient and Recyclable Ionic Liquid-Enabled Catalytic Greener Approach to One-Step Synthesis of Flavoring Ketones

Cellulose (CL) is widely available from the renewable biomaterial on the earth with a large number of hydroxyl functionalities on its surface. The appropriate modification of these functionalities results in the acidic and basic nature of the surface. In this work, the phosphoric group-functionalized CL ionic liquid (IL) has been successfully synthesized through phosphorylation of the CL surface. The phosphorus functionalization of CL has been carried out in two steps; first, synthesis of IL (3, 5-lutidinium methyl phosphate [Lut][(MeO)(H)PO2]), followed by phosphorylation of cellulose (CLP-IL). Subsequently, CLP-IL has been characterized by various physicochemical techniques. Significant changes in the activity were observed, with marginal changes in the structural and morphological properties of the native CL. CLP-IL has been utilized to synthesize industrially important flavoring ketones (FKs) via one-step alkylation–decarboxylation of active methylene compounds with substituted benzyl alcohols and halides. The functionalized CL IL could be quickly recovered in water and recycled at least five times without losing the catalytic activity. The optimized protocol has been successfully employed for the synthesis of FKs with an excellent conversion of substituted benzyl carbons in the range (90–100%) with 70–90% isolated yield of desired market valuable products. Furthermore, the mechanism was established by identifying the intermediates by physicochemical methods.

Research on the degradation behaviors of wood pulp cellulose in ionic liquids

Utilizing phosphate-based ionic liquids (ILs) solvents for dissolving cellulose to prepare cellulose fibers has attracted much attention for its convenience, high yield, stability and sustainability. However, the degradation behavior during dissolving of cellulose in ILs, which is an important factor for fabricating cellulose fiber, is still unclear. In this work, the degradation of wood pulped cellulose (WPC) in three kinds of phosphate-based ILs: 1-ethyl-3-methylimidazolium dimethyl phosphate ([Emim]DMP), 1-ethyl-3-methylimidazolium diethyl phosphate ([Emim]DEP) and 1-butyl-3-ethylimidazolium diethyl phosphate ([Beim]DEP), were systematically investigated at different dissolution temperatures and dissolution times. The results indicated that the degradation degree of WPC in three ILs follows the order of [Emim]DEP > [Beim]DEP > [Emim]DMP, which is consistent with interaction results obtained by quantum chemical calculation, and degradation degree increases follows the rising of dissolution temperature and the accumulation of dissolution time. Moreover, no reducing sugar (RS) was found in any recycled ILs even when the degree of polymerization (DP) of regenerated cellulose (RC) decreased by 30.4%. In addition, according to the Fourier transform infrared and X-ray diffraction data, the results further proved that the crystallization type of RC changed from type Ⅰ to type Ⅱ. Here, preferable dissolving parameters and experiments data of multiple conditions are provided, which may provide practical reference and guidance for both scientific research and industrial.

The solution state and dissolution process of cellulose in ionic-liquid-based solvents with different hydrogen-bonding basicity and microstructures

We demonstrated a clear and comprehensive description of the solution state, dissolution process, and regulation principle of cellulose in ionic liquids (ILs) and IL/co-solvent systems.

Bio-based chitosan and cellulose ionic liquid gels: polymeric soft materials for the desulfurization of fuel

Bio-based ionic liquid gels are new efficient soft materials, exhibiting convenient mechanical properties, that can be applied in the desulfurization of fuel to prevent air pollution.

UV-Sensing Cellulose Fibers Manufactured by Direct Incorporation of Photochromic Minerals

Textile-based wearable sensors integrated into daily wear offer opportunities for on-demand, real-time self-diagnosis to monitor health conditions with changing environmental surroundings and hazards. One still underrated environmental hazard is accumulated UV irradiation, causing skin burns, accelerated aging, and skin cancers. Here, we have demonstrated a sustainable fiber manufacture process to integrate photochromic hackmanite micro-particles directly into a cellulose body to achieve UV-sensing functionality in daily-life textiles. The hackmanite particles were dispersed into an ionic liquid cellulose dope using ultrasonication and nanofibrillated cellulose as a dispersant, resulting in good spinnability. The obtained fibers possess high mechanical strength with up to 10% photochromic hackmanite loading. To demonstrate its application in wearable UV sensors, the fibers were spun into yarn and then knitted into a piece of jersey fabric. The coloration of hackmanite-incorporated textiles under UV irradiation is readily quantified by image analysis using red–green–blue ratios, which was further utilized for UV dosimetry with a smartphone application showcasing the practical use of the UV sensor. The UV-sensing functionality remained the same after intensive washing and abrasion tests, further demonstrating the feasibility of its application in everyday garments.

Dissolution of Cellulose in Ionic Liquid-DMSO Mixtures: Roles of DMSO/IL Ratio and the Cation Alkyl Chain Length.

The dissolution behavior of cellulose in the mixtures of dimethyl sulfoxide (DMSO) and different ionic liquids (ILs) at 25 °C was studied. High solubility of cellulose was reached in the mixtures of ILs and DMSO at mole fractions of 1:2, 1:2, and 1:1 for 1-butyl-3-methylimidazolium acetate, 1-propyl-3-methylimidazolium acetate, and 1-ethyl-3-methylimidazolium acetate, respectively. At high DMSO/IL molar ratios (10:1–2:1), a longer alkyl chain of the IL cation led to higher cellulose solubility. However, shorter cation alkyl chains favored cellulose dissolution at 1:1. Rheological, Fourier transform infrared spectroscopy (FTIR), and nuclear magnetic resonance (NMR) measurements were used to understand cellulose dissolution. It was found out that the increase of the DMSO ratio in binary mixtures caused higher cellulose solubility by decreasing the viscosity of systems. For cations with longer alkyl chains, stronger interaction between the IL and cellulose and higher viscosity of DMSO/IL mixtures were observed. The new knowledge obtained here could be useful to the development of cost-effective solvent systems for biopolymers.