Production of Nanocellulose Using Hydrated Deep Eutectic Solvent Combined with Ultrasonic Treatment

Ultrasound-Assisted sequential processing of barley straw using binary acidic and hydrated ternary deep eutectic solvents for nanocellulose production

This study aimed to valorise barley straw by using a binary acidic deep eutectic solvent (DES) made from choline chloride and lactic acid for biomass pretreatment, and a hydrated ternary DES (HDES) composed of betaine, oxalic acid, and water (BOW HDES) for downstream processing to produce nanocellulose. The ultrasound-assisted DES pretreatment significantly enhanced lignin and hemicellulose solubilisation, achieving an average lignin removal of 70.54 % and hemicellulose solubilisation of 69.58 % under optimal conditions. Purification of US-DES-treated solid residue resulted in a cellulose yield of 39.81 ± 1.47 % with a purity of 91.31 ± 0.93 %, comparable to or exceeding conventional fractionation methods. The yield of lignin-rich material was 9.40 ± 0.89 % with a lignin purity of 83.29 ± 1.57 %. Further, nanocellulose was produced using a sequential process comprising low-viscosity HDES treatment, which improved fibre swelling and solubilisation, followed by high-intensity ultrasound (HIUS) treatment for nanoscale defibrillation. DLS analysis of the optimal nanocellulose sample revealed that 77.8 % of nanoparticles had a diameter below 100 nm, demonstrating a high yield of nanoscale material. XRD analysis confirmed the preservation of the cellulose I crystalline structure throughout processing, ensuring structural integrity. These findings demonstrate an efficient and sustainable biorefinery approach for lignin, cellulose, and nanocellulose extraction from agricultural residues, offering potential for scalable nanocellulose production.

Recent progress of multifunctional nanocellulose-based pharmaceutical materials: A review

In the pharmaceutical industry, ongoing research and development focus on discovering new drug formulations that align with regulatory approvals. Recently, innovative drug delivery systems have been used to maximize therapeutic efficacy with a precision of sustained drug delivery in the disease management system. Nanocellulose (NCs) synthesized from abundant cellulose, have attracted wide attention for potential pharmaceutical applications due to their unique properties, such as biocompatibility, high surface area-to-volume ratio, extensive drug loading and binding capacity, controlled drug release efficiency, strength, and availability with various treatments and modification ability. Nevertheless, research on nanocarriers (NCs) in the pharmaceutical field faces several limitations and challenges. Key areas requiring further exploration include chemical consumption, energy intensity, effluent management, recovery processes from acid hydrolysis, reaction times, ecotoxicology, and overall development progress. This overview provides the applications of emerging nanocellulose. It gives a clue on the synthesis of sustainable NCs related to their different sources, pre- and post-modifications of NCs, and key properties in pharmaceutical sectors. Furthermore, it gives an overview of the current advancements, life cycle analysis, biosafety, and key property performance with a summary of challenges and future perspectives.

Nanocellulose Extraction from Biomass Waste: Unlocking Sustainable Pathways for Biomedical Applications

The escalating global waste crisis necessitates innovative solutions. This study investigates the sustainable production of nanocellulose from biomass waste and its biomedical applications. Cellulose-rich materials-including wood, textiles, agricultural residues, and food by-products-were systematically processed using alkaline, acid, and oxidative pretreatments to enhance fiber accessibility. Mechanical techniques, such as grinding and homogenization, combined with chemical methods like acid hydrolysis and 2,2,6,6-Tetramethylpiperidin-1-yl-oxyl (TEMPO) oxidation, were employed to successfully isolate nanocellulose. Post-treatment modifications, including surface coating and cross-linking, further tailored its properties for specific applications. The results demonstrated nanocellulose's biocompatibility, biodegradability, and functional versatility. In wound healing, it enhanced moisture management and exhibited antimicrobial properties. Its high surface area facilitated efficient drug loading and controlled release in drug delivery applications. Nanocellulose bioinks supported cell proliferation in 3D bioprinting for tissue engineering. Additional applications in biosensors and personal care products were also identified. This study advances sustainable materials science, aligning resource conservation with circular economy principles to address biomedical sector needs.

Nanocellulose Technologies: Production, Functionalization, and Applications in Medicine and Pharmaceuticals - A Review

This review provides a comprehensive analysis of nanocellulose production, characterization, and applications, with a particular focus on its use in membranes and films for healthcare applications. The diverse sources of nanocellulose, including wood-based materials, agricultural byproducts, algae, and bacteria, are explored, highlighting their renewability, environmental benefits, and adaptability for specialized applications. The review also examines various pretreatment and processing methods, such as mechanical, chemical, and enzymatic treatments, outlining their roles in achieving desirable nanocellulose properties. Additionally, surface modification techniques, including amidation and esterification, are discussed for enhancing compatibility, stability, and performance when nanocellulose is integrated into composite materials. A novel mechanochemical approach is highlighted as a sustainable and energy-efficient fibrillation technique that reduces the environmental impact of nanocellulose production. Furthermore, the chemical modification and functionalization of nanocellulose are analyzed to expand its capabilities in advanced biomedical applications, including tissue engineering scaffolds that provide structural support for cell growth, wound dressings that leverage nanocellulose's antimicrobial and moisture-retentive properties, and drug delivery systems that utilize its biocompatibility and tunable release characteristics. The review concludes with future research directions, emphasizing the need for continued optimization of processing techniques, hybrid material development, and stimuli-responsive nanocellulose systems to unlock new biomedical and industrial applications.

Extraction of Phenolic Compounds From Lavender (Lavandula angustifolia L.) Plant by Natural Deep Eutectic Solvent and Greenness Assessment of Analytical Method With Modified Green Analytical Procedure Index

In recent years, it has been important in terms of green technology and sustainability to promote the use of natural deep eutectic solvents (NADESs), especially those based on natural products, for the extraction of bioactive components with different functional properties from foods. Therefore, in this study, the effects of green extraction technology (ultrasonic-assisted extraction) and green solvents (NADESs) on the recovery of bioactive components from lavender (Lavandula angustifolia L.) were investigated and evaluated. In addition, the degree of greenness of the analytical method used during the study was determined using the modified green analytical procedure index (MoGAPI). In this context, the total phenolic content (TPC), total antioxidant capacity, and individual polyphenolic profiles of lavender extracts prepared with two different NADES were investigated by liquid chromatography-tandem mass spectrophotometer. Based on the results obtained, it was determined that NADES formed with choline chloride:formic acid (ChCl:FA) had a higher potential to extract bioactive components from lavender than NADES formed with ChCl:ethylene glycol (ChCl:EG). The TPC, antioxidant capacity, and total individual polyphenolic compound content of lavender extracted with these NADES were determined as 9.76 mg gallic acid equivalent/g, 20.83-104.39 mg Trolox equivalent/g, and 200.835 mg/kg, respectively. However, the degree of greenness determined by the MoGAPI tool of the analytical method used in this study was 78% and classified as 'excellent green'. As a result, it can be concluded that NADES formed with ChCl:FA can be an alternative to conventional solvents for the extraction of bioactive components from lavender, as it provides a remarkable recovery of bioactive substances.

Green solvent-based extraction of cellulose from hemp bast fibers: From treatment efficacy to characterizations and optimization

This study assessed the efficacy of deep eutectic solvents (DESs) as green solvents for cellulose extraction from hemp bast fiber. Three DES mixtures were applied, and the combination of choline chloride and glycerol was selected for further experimentation due to its superior performance. The impact of four key parameters- treatment time, treatment temperature, DES-to-hemp ratio, and glycerol-to-choline chloride ratio was analyzed using Central-Composite Design (CCD) within response surface methodology (RSM) to optimize cellulose extraction. The optimal conditions achieved cellulose: lignin ratio of 70.817. Machine learning (ML) algorithms, including Multilayer Perceptron, Instance-Based Learner (IBK), Random Committee, Random Forest and Random Tree were conducted to predict the extraction process based on the RSM results. The results showed that the Random Tree demonstrated superiority by providing a predicted R2 value of 0.8548. Various characterization techniques such as SEM, FTIR, TGA, and XRD confirmed the removal of impurities. TGA and XRD results indicate a crystallinity index of 81.4 % and an increase in cellulose yield from 58.108 % in untreated hemp to 69.731 % in the h-12 sample, respectively, consistent with RSM findings. These findings indicate the high potential of DES as a green, cost-effective, and environmentally friendly solvent for cellulose extraction from hemp.

Catalytic conversion of chitin biomass into key platform chemicals

Chitin is the most abundant nitrogen-containing biomass on Earth and presents a compelling alternative to fossil fuels for chemical production. The catalytic conversion of chitin offers a viable approach for harnessing its inherent carbon and nitrogen contents, contributing to developing a green and sustainable society. This feature article reviews recent advances in shell waste biorefinery, with an emphasis on the contributions from our group. Efficient and sustainable chitin extraction methods are highlighted, along with the conversion of chitin biomass (N-acetyl-D-glucosamine (NAG), D-glucosamine, chitosan, and chitin) into key platform chemicals, mainly including furans, amino/amide sugars, organic acids and amino/amide acids. Catalytic strategies and production pathways are detailed, and current challenges and future research directions in chitin valorization are discussed.

Surface modification of cellulose nanocrystals for biomedical and personal hygiene applications

The increasing demand for sustainable and effective materials in biomedical and personal hygiene applications has driven the exploration of cellulose nanocrystals (CNCs) derived from biomass. These nanomaterials are highly valued for their exceptional mechanical properties, biocompatibility, and renewable nature. Researchers are exploring CNCs for advancing medical and hygiene products, but surface modification is often needed to maximize their benefits. Techniques such as chemical functionalization, physical coating, and hybridization can significantly enhance CNCs dispersibility, stability, and interaction with biological systems. This versatility makes CNCs suitable for a variety of applications, including drug delivery systems, wound dressings, and personal hygiene products. Despite their advantages, maintaining the inherent properties of CNCs while integrating new functionalities through modification poses a challenge. Understanding the impact of various modification techniques on CNC performance is crucial for optimizing their effectiveness. This review aimed to consolidate current knowledge on the surface modification of biomass-derived CNCs, offering insights into different methods and their implications for biomedical and personal hygiene applications. By highlighting advancements, challenges, and prospects, it served as a crucial resource for advancing the development and application of CNCs in these critical fields.

Choline chloride - oxalic acid dihydrate deep eutectic solvent pretreatment of Barley straw for production of cellulose nanofibers

This study investigates the production of cellulose nanofibers (CNF) from Barley straw using ultrasound-assisted deep eutectic solvent (US-DES) treatment for biomass fractionation and subsequent high-intensity ultrasonication (HIUS) for nano-fibrillation. Two deep eutectic solvents (DES), synthesized from choline chloride (ChCl) and oxalic acid dihydrate (OAD) at 1:1 and 2:1 M ratio, achieved solubilisation of over 80 % of lignin and hemicellulose under optimal conditions. The purification of these DES-treated materials resulted in cellulose with a purity >88 %. CNFs, characterized by a size of <100 nm, a polydispersity index under 0.5, and a zeta potential lower than -30 mV, were successfully isolated through a combination of wet grinding and HIUS treatment. SEM and XRD results showed the formation of a network of interconnected fibres with a Type I cellulose structure. This research highlights Barley straw's potential as a sustainable source of high-value CNF from agricultural waste.

Creation of Composite Aerogels Consisting of Activated Carbon and Nanocellulose Blended with Cross-Linked Biopolymers: Application as Ethylene Scavengers

This study involved producing aerogels using activated carbon (AC) and nanocellulose (NC). Two distinct structured composites, AC composite aerogel (ACCA) and NC composite aerogel (NCCA), were developed by separately mixing AC and NC with identical proportions of cross-linked biopolymers: hydroxypropyl methylcellulose (HPMC), methylcellulose (MC), and chitosan (C). These aerogels were evaluated for their capability to adsorb ethylene gas through batch experiments, while the physical and chemical characteristics were thoroughly examined to determine their feasibility of removing ethylene. The resulting ACCA and NCCA aerogels exhibited low densities of 0.094 g cm-3 and 0.077 g cm-3, respectively, coupled with high porosity ranging between 95 and 96%. During the ethylene adsorption test, NCCA exhibited superior ethylene removal rates (~14.88-16.77 mL kg-1) compared to ACCA (~13.57-14.97 mL kg-1). Specifically, NCCA achieved a removal efficiency of 83.86% compared to 74.64% for ACCA. Kinetic model fitting yielded high R2 values ranging from 0.97 to 0.98 with the Lagergren kinetic model. These findings suggest the potential of composite aerogels to be incorporated into food packaging materials for dynamic ethylene capture, independent of environmental conditions, thereby providing promising routes for further development.

High-Value Utilization of Cellulose: Intriguing and Important Effects of Hydrogen Bonding Interactions─A Mini-Review

Cellulose has been widely used in papermaking, textile, and chemical industries due to its diverse sources, environmental friendliness, and renewability. Recently, much more attention has been paid to converting cellulose into high-value-added products. Therefore, the extraction of nanocellulose, the dissolution of cellulose, and their applications are some of the most important research topics currently. However, cellulose's dense hydrogen bond network poses challenges for efficient extraction and dissolution, limiting its potential for functional material development. This review discusses the mechanisms of hydrogen bond disruption and weak interactions during nanocellulose extraction and cellulose dissolution. Key challenges and future research directions are highlighted, emphasizing developing efficient, ecofriendly, and cost-effective methods. Additionally, this review provides theoretical insights for constructing high-performance cellulose-based materials.

Lignocellulosic biomass-derived functional nanocellulose for food-related applications: A review

In recent years, nanocellulose (NC) has gained significant attention due to its remarkable properties, such as adjustable surface chemistry, extraordinary biological properties, low toxicity and low density. This review summarizes the preparation of NC derived from lignocellulosic biomass (LCB), including cellulose nanofibrils (CNF), cellulose nanocrystals (CNC), and lignin-containing cellulose nanofibrils (LCNF). It focuses on examining the impact of non-cellulosic components such as lignin and hemicellulose on the functionality of NC. Additionally, various surface modification strategies of NC were discussed, including esterification, etherification and silylation. The review also emphasizes the progress of NC application in areas such as Pickering emulsions, food packaging materials, food additives, and hydrogels. Finally, the prospects for producing NC from LCB and its application in food-related fields are examined. This work aims to demonstrate the effective benefits of preparing NC from lignocellulosic biomass and its potential application in the food industry.

Synthesis, functionalization, and commercial application of cellulose-based nanomaterials

In recent times, cellulose, an abundant and renewable biopolymer, has attracted considerable interest due to its potential applications in nanotechnology. This review explores the latest developments in cellulose-based nanomaterial synthesis, functionalization, and commercial applications. Beginning with an overview of the diverse sources of cellulose and the methods employed for its isolation and purification, the review delves into the various techniques used for the synthesis of cellulose nanocrystals (CNCs) and cellulose nanofibers (CNFs), highlighting their unique properties and potential applications. Furthermore, the functionalization strategies employed to enhance the properties and tailor the functionalities of cellulose-based nanomaterials were discussed. The review also provides insights into the emerging commercial applications of cellulose-based nanomaterials across diverse sectors, including packaging, biomedical engineering, textiles, and environmental remediation. Finally, challenges and prospects for the widespread adoption of cellulose-based nanomaterials are outlined, emphasizing the need for further research and development to unlock their full potential in sustainable and innovative applications.

DES-ultrasonication treatment of cellulose nanocrystals and the reinforcement in carrageenan biocomposite

CNCs are intensively studied to reinforce biocomposites. However, it remains a challenge to homogeneously disperse the CNC in biocomposites for a smooth film surface. Mechanochemical treatment via ultrasonication in deep eutectic solvent (DES) generated a stable dispersion of CNC before incorporation into carrageenan biocomposite. Shifted peaks of choline chloride (ChCl) methylene groups to 3.95-3.98 ppm in 1H NMR indicated a formation of eutectic mixture between the hydrogen bond acceptor (HBA) and hydrogen bond donor (HBD) at the functional group of CH3···OH. The swelling of CNC in the DES was proven by the formation of intermolecular H-bond at a length of 2.46 Å. The use of DES contributed to a good dispersion of CNC in the solution which increased zeta potential by 43.2 % compared to CNC in deionized water. The ultrasonication amplitude and feed concentration were varied for the best parameters of a stable dispersion of CNC. The crystallinity of 1 wt% of CNC at 20 % sonication amplitude improved from 76 to 81 %. The high crystallinity of CNCDES resulted in an increase in film tensile and capsule loop strength of Carra-CNCDES by 20.7 and 19.4 %, respectively. Improved dispersion of CNCDES reduced the surface roughness of the biocomposite by 21.8 %. H-bond network in CNCDES improved the biocomposite properties for an ingenious reinforcement material.

Nanocellulose Grades with Different Morphologies and Surface Modification as Additives for Waterborne Epoxy Coatings

While adding different micro- and nanocellulose types into epoxy coating formulations with waterborne phenalkamine crosslinker, effects on processing conditions and coating performance were systematically investigated. The variations in viscosity, thermal and thermomechanical properties, mechanical behavior, abrasive wear, water contact angles, and coating morphologies were evaluated. The selected additives include microcrystalline cellulose (MCC) at 1 to 10 wt.% and cellulose nanocrystals (CNC), cellulose nanofibers (CNF), cellulose microfibers (CMF), and hydrophobically modified cellulose microfibers (mCMF) at 0.1 to 1.5 wt.%. The viscosity profiles are determined by the inherent additive characteristics with strong shear thinning effects for epoxy/CNF, while the epoxy/mCMF provides lower viscosity and better matrix compatibility owing to the lubrication of encapsulated wax. The crosslinking of epoxy/CNF is favored and postponed for epoxy/(CNC, CMF, mCMF), as the stronger interactions between epoxy and CNF are confirmed by an increase in the glass transition temperature and reduction in the dampening factor. The mechanical properties indicate the highest hardness and impact strength for epoxy/CNF resulting in the lowest abrasion wear rates, but ductility enhances and wear rates mostly reduce for epoxy/mCMF together with hydrophobic protection. In addition, the mechanical reinforcement owing to the specific organization of a nanocellulose network at percolation threshold concentrations of 0.75 wt.% is confirmed by microscopic analysis: the latter results in a 2.6 °C (CNF) or 1.6 °C (CNC) increase in the glass transition temperature, 50% (CNF) or 20% (CNC) increase in the E modulus, 37% (CNF) or 32% (CNC) increase in hardness, and 58% (CNF) or 33% (CNC) lower abrasive wear compared to neat epoxy, while higher concentrations up to 1.5 wt.% mCMF can be added. This research significantly demonstrates that nanocellulose is directly compatible with a waterborne phenalkamine crosslinker and actively contributes to the crosslinking of waterborne epoxy coatings, changing the intrinsic glass transition temperatures and hardness properties, to which mechanical coating performance directly relates.

Promoting the disassemble and enzymatic saccharification of bamboo shoot shells via efficient hydrated alkaline deep eutectic solvent pretreatment

Pretreatment is a key process restricting the development of biorefinery. This work developed a pretreatment process based on an ethanolamine/acetamide alkaline deep eutectic solvent (ADES). Under microwave assistance, pure ADES pretreatment at 100 °C for 10 min achieved 95.9 % delignification and 95.2 % hemicellulose removal of bamboo shoot shells (BSS). Further, when 75 % water was added to pure DES to prepare hydrated DES (75 %-HADES), impressive delignification (93.2 %), hemicellulose removal (92.2 %) and cellulose recovery (94.8 %) were still achieved. The cellulose digestibility of the 75 %-HADES pretreated solid residue was significantly increased from 12.2 % (the control) to 91.2 %. Meanwhile, the structural features of hemicellulose and lignin macromolecules fractionated by 75 %-HADES pretreatment were well preserved, offering opportunities for downstream utilization. Overall, this work proposes an effective pretreatment strategy with the potential to enable the utilization of all major components of bamboo shoot shells.

Process design for acidic and alcohol based deep eutectic solvent pretreatment and high pressure homogenization of palm bunches for nanocellulose production

This research aimed to study on nanocellulose production from palm bunch using process design and cost analysis. Choline chloride based deep eutectic solvent pretreatment was selected for high-purity cellulose separation at mild condition, followed by nano-fibrillation using mechanical treatment. Three types of choline chloride-based deep eutectic solvents employing different hydrogen-bond donors (HBDs) namely lactic acid, 1,3-butanediol and oxalic acid were studied. The optimal cellulose extraction condition was choline chloride/lactic acid (ChLa80C) pretreatment of palm empty bunch at 80 °C followed by bleaching yielding 94.96%w/w cellulose content in product. Size reduction using ultrasonication and high-pressure homogenization produced nanocellulose at 67.12%w/w based on cellulose in raw material. Different morphologies of nanocellulose were tunable in the forms of nanocrystals, nano-rods and nanofibers by using dissimilar deep eutectic solvents. This work offered a sustainable and environmentally friendly process as well as provided analysis of DES pretreatment and overview operating cost for nanocellulose production. Application of nanocellulose for the fabrication of highly functional and biodegradable material for nanomedicine, electronic, optical, and micromechanical devices is achievable in the near future.

Sono-Microwave Assisted Chlorine free and Ionic Liquid (SMACIL) extraction of cellulose from Urtica dioica: A benign to green approach

The extraction of cellulose using eco-friendly solvents has been gaining significant attention for a couple of decades. This study investigated the impact of benign and green solvents on the extraction, thermal stability, mechanical properties, and crystallinity of cellulose extracted from Urtica dioica (Stinging nettle) using a Sono-Microwave Assisted Chlorine free and Ionic Liquid (SMACIL) extraction technique. In this regard, the stalks were undergone through pre chemical treatment before starting bleaching them with hydrogen peroxide (HPO) and 1-butyl-3-methylimidazolium acetate (BMIM-Ac) having different mole ratios (5, 7.5, and 10) to expose cellulose. The Urtica dioica cellulose (UDC) was characterized using FTIR, tensile testing, FESEM, XRD, and TGA. The fibrillation and lumen can be seen in SEM images that confirm the extraction of cellulose. The results showed that the BMIM-Ac-10 gives the maximum cellulose yield (88 %) than other compositions. Moreover, the cellulose extracted using BMIM-Ac-10 has high mechanical strength which makes it a potential constituent for various applications in the field of materials science. These results have significant implications for the development of sustainable and efficient processes for the extraction of cellulose.

Facile preparation of re-dispersible/amphoteric nanochitin powder via choline chloride/propanedioic composite for stabilizing Pickering emulsions

Choline chloride (ChCl)/propanedioic acid (PA) based hydrated composites are synthesized for producing nanochitins from crab shell in this work. The yield of nanochitin remains higher than 75 %, even if the water content reaches 80 %. ChCl is found necessary for the successful nano-fibrillation of chitin. However, PA contributes more to the yield improvement of nanochitin. ChCl mediated PA hydrolysis leads to the successful grafting of carboxyl groups in nanochitins, contributing to its amphoteric dispersed nature. After salt-induced separation and freeze-drying treatment, dried nanochitin powder can be prepared and found to disperse well either in acidic or alkaline suspension, exhibiting efficient drying/redispersion performance. The well amphoteric and drying/redispersion nature both benefit the facile preparation of nanochitin-based Pickering emulsions. For Pickering emulsion prepared under different pH, creaming only appears under acidic conditions (pH 3) for which the creaming index reaches 10.56 % after 30 days of storage. No obvious de-emulsification can be observed under pH 7 and 10. The efficient amphoteric and drying/redispersion nature together with the simplified preparation process of nanochitins are believed to facilitate the processing and practical applications of nanochitin.

Efficient extraction of nanocellulose from lignocellulose using aqueous butanediol fractionation to improve the performance of waterborne wood coating

The highly efficient extraction of cellulose from lignocellulose with an excellent yield of 95.2 % and purity of 96.7 % was demonstrated using acid-catalyzed fractionation with aqueous butanediol. This cellulose was subsequently transformed into cellulose nanofibers (CNFs) and cellulose nanocrystals (CNCs) with specific dimensions and surface functional groups through various chemomechanical treatments. The average diameters of CNFs and CNCs produced by sulfuric acid hydrolysis-ultrasonication and deep eutectic solvent treatment-ultrasonication (DES-CNCs) were 29.7, 21.9 and 17.3 nm, respectively. The DES-CNCs were obtained in a good yield of 71 ± 1.27 wt% and exhibited a high zeta potential of -33.5 ± 2.51 mV following posthydrolysis and esterification during the DES treatment. These CNFs and CNCs were used as nanofillers in a waterborne wood coating (WWC), which significantly improved its dynamic viscosity and storage modulus. The addition of these materials also enhanced the mechanical strength of the WWC but had little effect on transmittance. Glossiness, hardness, abrasion resistance and adhesion strength were evaluated, and the DES-CNCs provided the greatest improvements at a low concentration. A plausible reinforcement mechanism was presented. This work provided an efficient cellulose extraction method and detailed structure elucidation of the nanocellulose together with suggestions for value-added applications of cellulosic nanofillers for reinforcing WWC.

Controlling the critical parameters of ultrasonication to affect the dispersion state, isolation, and chiral nematic assembly of cellulose nanocrystals

Cellulose nanocrystals (CNCs) are typically extracted from plants and present a range of opto-mechanical properties that warrant their use for the fabrication of sustainable materials. While their commercialization is ongoing, their sustainable extraction at large scale is still being optimized. Ultrasonication is a well-established and routinely used technology for (re-) dispersing and/or isolating plant-based CNCs without the need for additional reagents or chemical processes. Several critical ultrasonication parameters, such as time, amplitude, and energy input, play dominant roles in reducing the particle size and altering the morphology of CNCs. Interestingly, this technology can be coupled with other methods to generate moderate and high yields of CNCs. Besides, the ultrasonics treatment also has a significant impact on the dispersion state and the surface chemistry of CNCs. Accordingly, their ability to self-assemble into liquid crystals and subsequent superstructures can, for example, imbue materials with finely tuned structural colors. This article gives an overview of the primary functions arising from the ultrasonication parameters for stabilizing CNCs, producing CNCs in combination with other promising methods, and highlighting examples where the design of photonic materials using nanocrystal-based celluloses is substantially impacted.

Cellulose Isolation from Tomato Pomace: Part II-Integrating High-Pressure Homogenization in a Cascade Hydrolysis Process for the Recovery of Nanostructured Cellulose and Bioactive Molecules

This work proposes a biorefinery approach for utilizing tomato pomace (TP) through a top-down deconstructing strategy, combining mild chemical hydrolysis with high-pressure homogenization (HPH). The objective of the study is to isolate cellulose pulp using different combinations of chemical and physical processes: (i) direct HPH treatment of the raw material, (ii) HPH treatment following acid hydrolysis, and (iii) HPH treatment following alkaline hydrolysis. The results demonstrate that these isolation routes enable the production of cellulose with tailored morphological properties from TP with higher yields (up to +21% when HPH was applied before hydrolysis and approximately +6% when applied after acid or after alkaline hydrolysis). Additionally, the side streams generated by this cascade process show a four-fold increase in phenolic compounds when HPH is integrated after acid hydrolysis compared to untreated sample, and they also contain nanoparticles composed of hemicellulose and lignin, as shown by FT-IR and SEM. Notably, the further application of HPH treatment enables the production of nanostructured cellulose from cellulose pulp derived from TP, offering tunable properties. This approach presents a sustainable pathway for the extraction of cellulose and nanocellulose, as well as the valorization of value-added compounds found in residual biomass in the form of side streams.

A ternary eutectic solvent for cellulose nanocrystal production: exploring the recyclability and pre-pilot scale-up

Deep eutectic solvents (DES) formed using choline chloride (ChCl), p-toluenesulfonic acid (pTSA) of stoichiometry ChCl: pTSA (1:1) and (1:2), and its ternary eutectic mixtures with phosphoric acid (PA) 85% as an additive (ChCl: pTSA: PA) were evaluated for cellulose nanocrystal (CNC) isolation. Initially, the hydrolytic efficiency to produce CNC of each DES was compared before and after adding phosphoric acid by Hammett acidity parameters and the Gutmann acceptor number. Moreover, different DES molar ratios and reaction time were studied at 80°C for CNC optimization. The nanomaterial characteristics were analyzed by field emission scanning electron microscopy (FESEM), X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), and thermogravimetric analysis (TGA). The ternary eutectic mixture ChCl: pTSA: PA molar ratio (1:1:1.35) was chosen as a suitable recyclable ternary system at the laboratory scale. A CNC yield of about 80% was obtained from the hydrolysis of commercial cellulose in five cycles of recovery, but it dropped to 35% in pre-pilot scaling. However, no variation in the average size of the resulting CNC was observed (132 ± 50 nm x 23 ± 4 nm), which presented high thermal stability (Tmax 362°C) and high crystallinity of about 80% after 3 h of reaction time.

Mechanistic insights into the lignin dissolution behavior in amino acid based deep eutectic solvents

Deep eutectic solvents (DESs) composed by amino acids (L-arginine, L-proline, L-alanine) as the hydrogen bond acceptors (HBAs) and carboxylic acids (formic acid, acetic acid, lactic acid, levulinic acid) as hydrogen bond donors (HBDs) were prepared and used for the dissolution of dealkaline lignin (DAL). The mechanism of lignin dissolution in DESs was explored at molecular level by combining the analysis of Kamlet-Taft (K-T) solvatochromic parameters, FTIR spectrum and density functional theory (DFT) calculations of DESs. Firstly, it was found that the formation of new hydrogen bonds between lignin and DESs mainly drove the dissolution of lignin, which were accompanied by the erosion of hydrogen bond networks in both lignin and DESs. The nature of hydrogen bond network within DESs was fundamentally determined by the type and number of functional groups in both HBA and HBD, which affected its ability to form hydrogen bond with lignin. One hydroxyl group and carboxyl group in HBDs provided active protons, which facilitated proton-catalyzed cleavage of β-O-4, thus enhancing the dissolution of DESs. The superfluous functional group resulted in more extensive and stronger hydrogen bond network in the DESs, thus decreasing the lignin dissolving ability. Moreover, it was found that lignin solubility had a closed positive correlation with the subtraction value of α and β (net hydrogen donating ability) of DESs. Among all the investigated DESs, L-alanine/formic acid (1:3) with the strong hydrogen-bond donating ability (acidity), weak hydrogen-bond accepting ability (basicity) and small steric-hindrance effect showed the best lignin dissolving ability (23.99 wt%, 60 °C). On top of that, the value of α and β of L-proline/carboxylic acids DESs showed some positive correlation with the global electrostatic potential (ESP) maxima and minima of the corresponding DESs respectively, indicating the analysis of ESP quantitative distributions of DESs could be an effective tool for DESs screening and design for lignin dissolution as well as other applications.

Dissolution of lignocellulose with high lignin content in AlCl3/ZnCl2 aqueous system and properties of the regenerated cellulose film

Herein, a novel method for dissolving lignocellulose at room temperature is proposed by combining deep eutectic solvents (DES) pretreatment and subsequent dissolution in AlCl₃/ZnCl₂ aqueous system. Results showed that DES pretreatment could significantly increase the dissolubility of lignin-containing cellulose (CL) samples in AlCl₃/ZnCl₂ aqueous system. The dissolution ratio of the CL sample with 15.6 % lignin content in AlCl₃/ZnCl₂·3H₂O solvent was as high as 90 %. Besides, the mechanism for the remarkable dissolution of CL samples in low water AlCl₃/ZnCl₂ aqueous solvent was also proposed. Moreover, the dissolved CL sample was regenerated for the production of lignocellulose films, which have excellent ultraviolet (UV) blocking, hydrophobic, mechanical strength, and natural degradation properties. In particular, the films could be completely naturally degraded after 10 days, which provided a promising way to prepare biodegradable lignocellulose materials, and to encourage the potential utilization of renewable lignocellulose in packaging industry.

Understanding Nanocellulose-Water Interactions: Turning a Detriment into an Asset

Modern technology has enabled the isolation of nanocellulose from plant-based fibers, and the current trend focuses on utilizing nanocellulose in a broad range of sustainable materials applications. Water is generally seen as a detrimental component when in contact with nanocellulose-based materials, just like it is harmful for traditional cellulosic materials such as paper or cardboard. However, water is an integral component in plants, and many applications of nanocellulose already accept the presence of water or make use of it. This review gives a comprehensive account of nanocellulose-water interactions and their repercussions in all key areas of contemporary research: fundamental physical chemistry, chemical modification of nanocellulose, materials applications, and analytical methods to map the water interactions and the effect of water on a nanocellulose matrix.

Cellulose: A Review of Water Interactions, Applications in Composites, and Water Treatment

Cellulose is known to interact well with water, but is insoluble in it. Many polysaccharides such as cellulose are known to have significant hydrogen bond networks joining the molecular chains, and yet they are recalcitrant to aqueous solvents. This review charts the interaction of cellulose with water but with emphasis on the formation of both natural and synthetic fiber composites. Covering studies concerning the interaction of water with wood, the biosynthesis of cellulose in the cell wall, to its dispersion in aqueous suspensions and ultimately in water filtration and fiber-based composite materials this review explores water-cellulose interactions and how they can be exploited for synthetic and natural composites. The suggestion that cellulose is amphiphilic is critically reviewed, with relevance to its processing. Building on this, progress made in using various charged and modified forms of nanocellulose to stabilize oil-water emulsions is addressed. The role of water in the aqueous formation of chiral nematic liquid crystals, and subsequently when dried into composite films is covered. The review will also address the use of cellulose as an aid to water filtration as one area where interactions can be used effectively to prosper human life.

Recent advances in cellulose microgels: Preparations and functionalized applications

Microgels are soft, deformable, permeable, and stimuli-responsive microscopic polymeric particles that are now emerging as prospective multifunctional soft materials for delivery systems, interface stabilization, cell cultures and tissue engineering. Cellulose microgels are emerging biopolymeric microgels with unique characteristics such as abound hydroxyl structure, admirable designability, multiscale pore network and excellent biocompatibility. This review summarizes the fabrication strategies for microgel, then highlights the fabrication routes for cellulose microgels, and finally elaborates cellulose microgels' bright application prospects with unique characteristics in the fields of controlled release, interface stabilization, coating, purification, nutrition/drug delivery, and bio-fabrication. The challenges to be addressed for further applications and considerable scope for development in future of cellulose microgels are also discussed.

Cellulose Nanofibers Derived Surface Coating in Enhancing the Dye Removal with Cellulosic Ultrafiltration Membrane

Commercially available ultrafiltration membranes were coated with cellulose nanofibers (CNFs) produced from softwood pulp by a two-step process: a non-derivatizing DES treatment and a simple mechanical treatment (high-speed homogenization and sonification). The CNFs coating aimed at enhancement of the removal of methylene blue (MB) from water and was investigated at different concentrations of the coating, quantified in grams of CNFs per square meter of the membrane (1.3, 6.5, 13, and 19.5 g/m²). The pure water permeability (PWP) was unaffected up to the concentration of 6.5 g/m² but the dye retention increased approximately 2.5-fold. Even higher improvement of MB removal, about 4-fold, was observed when 19.5 g/m² were used, however, the pure water permeability also decreased by about 30%. In addition, it was proved that the coating can be removed and created again several times which shows that the concept could be used to improve the retention of organic compounds when high permeability membranes are used.

Nanocrystalline cellulose derived from spruce wood: Influence of process parameters

The cellulose nanocrystals (CNCs) were produced from spruce wood using less hazardous and toxic reagents with understanding of influence of process parameters on CNCs properties. This study employed acetosolv pulping followed by alkaline-peroxide bleaching, eliminating highly reactive chemicals such as Na-chlorites and Na-sulfite for cellulose pulp extraction from spruce wood. Cellulose pulp yield of 41.5 ± 0.7 wt% of dry wood was obtained from pulping followed by bleaching treatment. Cellulose pulp was hydrolyzed with 59.0-65.0 wt% sulfuric acid followed by ultrasonic treatment to produce CNCs. CNCs yield of 8.0 ± 3.2 wt% of dry wood was obtained at 65 wt% acid concentration and yield of 25.1 ± 0.7 wt% at 62 wt% acid concentration. The optimization of acid hydrolysis and ultrasonic treatment resulted in CNCs with high aspect ratios (length/width) up to 48.1. It was demonstrated that higher acid concentration requires lower intensity of ultrasonic treatment for CNCs dispersion, and that higher intensity could enhance aspect ratio without impacting the crystallinity index. However, ultrasonic treatment for longer than 5 min led to destruction of the whisker morphology of CNCs. The extracted CNCs possess high crystallinity index of 80.8 ± 1.7 %, low residual hemicellulose (<2.0 %) and lignin (<0.7 %), and high-char content of 26.7 wt% from thermal degradation.

Biomedical engineering aspects of nanocellulose: a review

Cellulose is one of the most abundant renewable biopolymer in nature and is present as major constituent in both plant cell walls as well as synthesized by some microorganisms as extracellular products. In both the systems, cellulose self-assembles into a hierarchical ordered architecture to form micro to nano-fibrillated structures, on basis of which it is classified into various forms. Nanocellulose (NCs) exist as rod-shaped highly crystalline cellulose nanocrystals to high aspect ratio cellulose nanofibers, micro-fibrillated cellulose and bacterial cellulose (BC), depending upon the origin, structural and morphological properties. Moreover, NCs have been processed into diversified products ranging from composite films, coatings, hydrogels, aerogels, xerogels, organogels, rheological modifiers, optically active birefringent colored films using traditional-to-advanced manufacturing techniques. With such versatility in structure-property, NCs have profound application in areas of healthcare, packaging, cosmetics, energy, food, electronics, bioremediation, and biomedicine with promising commercial potential. Herein this review, we highlight the recent advancements in synthesis, fabrication, processing of NCs, with strategic chemical modification routes to tailor its properties for targeted biomedical applications. We also study the basic mechanism and models for biosynthesis of cellulose in both plant and microbial systems and understand the structural insights of NC polymorphism. The kinetics study for both enzymatic/chemical modifications of NCs and microbial growth behavior of BC under various reactor configurations are studied. The challenges associated with the commercial aspects as well as industrial scale production of pristine and functionalized NCs to meet the growing demands of market are discussed and prospective strategies to mitigate them are described. Finally, post chemical modification evaluation of biological and inherent properties of NC are important to determine their efficacy for development of various products and technologies directed for biomedical applications.

Enhancing the potential production of bioethanol with bamboo by γ-valerolactone/water pretreatment

In this study, the effect of the γ-valerolactone (GVL)/H2O pretreatment system on bamboo (Neosinocalamus affinis) for enzymatic hydrolysis and ethanol fermentation was investigated. The performance characterization of the pretreated bamboo substrates, including the chemical composition, the structural characteristics, and the ability to produce bioethanol, were evaluated. The recovered substrates were enzymatically hydrolyzed for 48 h and then fermented to bioethanol. For the cellulose in the raw bamboo material, the highest cellulose-to-glucose conversion yield (CGCY) was achieved at 140 °C for 2 h with GVL : H2O = 8 : 2, which was 73.39%, and the cellulose-to-ethanol conversion yield (CECY) was 67.00%. This indicated that 183.5 kg of bioethanol could be produced per ton of bamboo, which was 9.71-folds higher than that directly converted from the untreated raw bamboo powder. Under these conditions, 50.60% of the active lignin can be recovered and be used as a wood-derived feedstock for further high-valued utilization. Meanwhile, the maximum concentration of fermentation inhibitors formed after pretreatment was about 140.9 mmol L-1, and had weak inhibition to the subsequent reaction. It has been shown that the cellulose could be effectively separated from bamboo and converted into bioethanol through the GVL/H2O pretreatment system.

The application of green solvent in a biorefinery using lignocellulosic biomass as a feedstock

The high dependence on crude oil for energy utilization leads to a necessity of finding alternative sustainable resources. Solvents are often employed in valorizing the biomass into bioproducts and other value-added chemicals during treatment stages. Unfortunately, despite the effectiveness of conventional solvents, hindrances such as expensive solvents, unfavourable environmental ramifications, and complicated downstream separation systems often occur. Therefore, the scientific community has been actively investigating more cost-effective, environmentally friendly alternatives and possess the excellent dissolving capability for biomass processing. Generally, 'green' solvents are attractive due to their low toxicity, economic value, and biodegradability. Nonetheless, green solvents are not without disadvantages due to their complicated product recovery, recyclability, and high operational cost. This review summarizes and evaluates the recent contributions, including potential advantages, challenges, and drawbacks of green solvents, namely ionic liquids, deep eutectic solvents, water, biomass-derived solvents and carbon dioxide in transforming the lignocellulosic biomass into high-value products. Moreover, research opportunities for future developments and potential upscale implementation of green solvents are also critically discussed.

Uniform rod and spherical nanocrystalline celluloses from hydrolysis of industrial pepper waste (Piper nigrum L.) using organic acid and inorganic acid

Conversion of lignocellulosic biowastes from agricultural industry into nanocrystalline cellulose provides pathway to reduce environmental pollution while enhancing the economic value of biowastes. Nanocellulose (NCC) with uniform morphology was isolated from pepper (Piper nigrum L.) stalk waste (PW) using acid hydrolysis method. The role of inorganic acids (sulfuric acid, hydrochloric acid, phosphoric acid), organic acids (oxalic acid, citric acid, acetic acid) and variation of sonication times were investigated on the physicochemical characteristics, self-assembled structure, crystallinity, particle size, zeta potential and thermal stability of the isolated nanocellulose. Hydrolysis using inorganic acids transformed cellulose from PW into a spherical shaped NCC at ~33-67 nm of average diameter. Meanwhile hydrolysis in organic acids produced rod-shaped NCC at 210-321 nm in length. This study highlighted the role of acidity strength for organic acid and inorganic acid in controlling the level of hydrogen bond dissociation and the dissolution of amorphous fragments, which consequently directing the morphology and the physicochemical properties of NCCs.

Screw extrusion pretreatment for high-yield lignocellulose nanofibrils (LCNF) production from wood biomass and non-wood biomass

To develop a facile and low-cost nanofibrils process with excellent feedstock adaptability, high-yield lignocellulose nanofibrils (LCNF) are produced directly from wood and non-wood biomass using glycerol solvent via screw extrusion pretreatment. Different LCNFs are obtained from four classical raw materials (polar, pine, bamboo, and wheat straw) in this research, followed by comparing their morphological, thermochemical, and mechanical properties. More than 70 wt% of LCNF could be obtained from low-cost substrates except for LCNF from wheat straw with 62.3 wt% yield. Besides, the morphology property of wood LCNF exhibit more uniform distribution over that of non-wood LCNF due to narrower size distribution. Strikingly, despite of the slightly lower LCNF crystallinity various from 52.4% to 62.6% obtained from four substrates, all the LCNFs separated from wood and non-wood biomass exhibit high thermal stability (T_max over 330 °C), which is higher than conventional nanocellulose, indicating that the crystal area could be well maintained during the pretreated process. Moreover, all the LCNF films show excellent tensile strength which is close to nanocellulose materials. Besides, the Young's modulus of wood-based LCNF films is higher than that of non-wood based LCNF films. Overall, LCNF with excellent performance could be achieved from low-cost biomass by our facile process, which provides a feasible route for industrial production of bio-based nanofilms.

Lytic polysaccharide monooxygenases as powerful tools in enzymatically assisted preparation of nano-scaled cellulose from lignocellulose: A review

Nanocellulose, either in the form of fibers or crystals, constitutes a renewable, biobased, biocompatible material with advantageous mechanical properties that can be isolated from lignocellulosic biomass. Enzyme-assisted isolation of nanocellulose is an attractive, environmentally friendly approach that leads to products of higher quality compared to their chemically prepared counterparts. Lytic polysaccharide monooxygenases (LPMOs) are enzymes that oxidatively cleave the β-1,4-glycosidic bond of polysaccharides upon activation of O₂ or H₂O₂ and presence of an electron donor. Their use for treatment of cellulose fibers towards the preparation of nano-scaled cellulose is related to the ability of LPMOs to create nicking points on the fiber surface, thus facilitating fiber disruption and separation. The aim of this review is to describe the mode of action of LPMOs on cellulose fibers towards the isolation of nanostructures, thus highlighting their great potential for the production of nanocellulose as a novel value added product from lignocellulose.

The role of deep eutectic solvents in the production of cellulose nanomaterials from biomass

In recent years, the demand for environment-friendly products has been on an increasing trend among researchers and industry for sustainable development. Deep eutectic solvents are green solvents which, due to their properties (biodegradability, recyclability, low cost, availability, easy preparation, low toxicity, chemical and thermal stability), can be used in various fields such as polymer chemistry, which includes nanocellulose isolation and polysaccharides processing. Several studies have illustrated the effectiveness of using deep eutectic solvents instead of the conventional reaction system to produce and disperse nanomaterials. This work summarizes the use of deep eutectic solvents in the isolation of cellulosic nanomaterials from different types of biomass. Deep eutectic solvents demonstrate high effectiveness in swelling lignocellulosic biomass and producing cellulose nanomaterials. Overall, deep eutectics solvents represent an innovative and effective pretreatment process for the fractionation of raw cellulose-containing fibres to promote subsequent isolation of nanomaterials made from cellulose.

Strengthening Cellulose Nanopaper via Deep Eutectic Solvent and Ultrasound-Induced Surface Disordering of Nanofibers

The route for the preparation of cellulose nanofiber dispersions from bacterial cellulose using ethylene glycol- or glycerol-based deep eutectic solvents (DES) is demonstrated. Choline chloride was used as a hydrogen bond acceptor and the effect of the combined influence of DES treatment and ultrasound on the thermal and mechanical properties of bacterial cellulose nanofibers (BC-NFs) is demonstrated. It was found that the maximal Young’s modulus (9.2 GPa) is achieved for samples prepared using a combination of ethylene glycol-based DES and ultrasound treatment. Samples prepared with glycerol-based DES combined with ultrasound exhibit the maximal strength (132 MPa). Results on the mechanical properties are discussed based on the structural investigations that were performed using FTIR, Raman, WAXD, SEM and AFM measurements, as well as the determination of the degree of polymerization and the density of BC-NF packing during drying with the formation of paper. We propose that the disordering of the BC-NF surface structure along with the preservation of high crystallinity bulk are the key factors leading to the improved mechanical and thermal characteristics of prepared BC-NF-based papers.

Insights into structure and properties of cellulose nanofibrils (CNFs) prepared by screw extrusion and deep eutectic solvent permeation

To achieve the balance on economy and ecology, it is indispensable to explore the greener and more inexpensive method for the production of cellulose nanofibrils (CNFs). Herein, a deep eutectic solvent (DES) system based on choline chloride (ChCl) and ethylene glycol (EG) was employed as the swollen solvent, combining with screw extrusion and permeant, to fabricate unmodified CNFs with high yield and thermal stability. The proposed method in this work was simple, convenient, and industrially viable. The hydrous DESs were applied in the process of CNFs preparation and dispersion to reduce the cost and viscosity of DES. To reveal the principle of CNFs preparation, the impact of sulfuric acid and water content of DES system on the chemical, physical, morphological, thermal, and dispersive properties of CNFs was systematically studied. Properties of the dispersed solvents were characterized by solvatochromic parameters and viscosity parameters to evaluate the potential influence on the preparation and dispersion of CNFs. In general, this work would play valuable guidance in realizing the preparation and dispersion of CNFs via a versatile DES solvent system, thus endowing cellulose materials high-value utilization.

Preparation and Characterization of Polybutylene Succinate Reinforced with Pure Cellulose Nanofibril and Lignocellulose Nanofibril Using Two-Step Process

This study reports the preparation of a polybutylene succinate (PBS) film reinforced with pure cellulose nanofibril (PCNF) and lignocellulose nanofibril (LCNF) by a two-step process that consists of solvent dispersion and twin-screw extrusion. Compared to the conventional one-step process, this method offered improved mechanical properties. The addition of 5% CNF increased the tensile properties up to 18.8%. Further, the effect of the lignin content was also studied by using LCNF as a reinforcement. The LCNF was prepared with and without a deep eutectic solvent (DES) pretreatment to gain LCNF with a lignin content that varied between 5, 19, and 30%. The mechanical properties results show that a 5% addition of LCNF to the PBS matrix increased its tensile strength and elastic modulus. Further, the morphological and thermal properties of the composites were also studied in detail.

Cellulose nanofibril as a crosslinker to reinforce the sodium alginate/chitosan hydrogels

Hydrogels derived from natural polymers have received great attention, but their practical applications are severely hindered by the relatively poor mechanical properties. In this work, cellulose nanofibril (CNF) was used as a crosslinker to reinforce the sodium alginate (SA)/chitosan (CS) hydrogels for drug sustained release. The CNF was prepared via a combined process of ball milling and deep eutectic solvents (DESs) pretreatment and characterized using SEM, FT-IR, and XRD. Furthermore, the microstructure, mechanical/biological properties and swelling performance of SA/CS/CNF hydrogels were investigated. Results showed that 1.0 wt% CNF addition led to the increases of 23.6% in storage modulus and 54.4% in loss modulus for the SA/CS/CNF hydrogels, indicating that CNF addition was effective in reinforcing the three-dimensional entangled networks of the hydrogels. Moreover, the presence of CNF was found to weaken the swelling performance of SA/CS/CNF hydrogels. When the synthesized SA/CS/CNF hydrogel with 1.0 wt% CNF was applied as a carrier for drug release, 50.8% reduction in the release rate in simulated gastric juice was achieved, demonstrating its outstanding sustained release properties. This work suggested that CNF might be conducive to enhancing the properties of SA/CS hydrogels, which can serve as an ideal polymeric carrier for drug release.

Molecular level insight into the solvation of cellulose in deep eutectic solvents

Deep eutectic solvents as sustainable and new-generation solvents show potential in the field of cellulose dissolution. Although these novel materials are tested for numerous industrial, environmental, and medical applications, little is known about the structural features of cellulose interacting with deep eutectic solvents. In this work, the interplay of cellulose is studied in two deep eutectic solvents: choline acetate mixed with urea and choline chloride mixed with urea using classical molecular dynamics simulations. Dissolution of cellulose in the studied liquids was not observed to be in agreement with experimental work from the literature. However, a slight swelling in the chloride, as compared to the acetate-based solvent, is apparent. A possible rationale might be found in the stronger hydrogen bonding of the chloride anion compared to the acetate anion with the hydrogen atoms of the cellulose. Moreover, chloride approaches the outer glucose units comparatively more, which could be interpreted as the onset of entering and thus dissolving the cellulose as was previously observed. Specific hydrogen bonds between all units are analyzed and discussed in detail.