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Facile dissolution of cellulose by superbase-derived ionic liquid using organic solvents as co-solvents at mild temperatures. Carbohydr Polym 2024; 330:121836. [PMID: 38368113 DOI: 10.1016/j.carbpol.2024.121836] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/26/2023] [Revised: 01/10/2024] [Accepted: 01/16/2024] [Indexed: 02/19/2024]
Abstract
Dissolving cellulose at low temperatures is a key step in its efficient utilization as a renewable resource to produce high-value-added platform chemicals and high-performance materials. Here, the potential of four aprotic organic solvents was investigated for use as co-solvents with a sustainable DBU-derived ionic liquid (SIL) for the low-temperature dissolution and regeneration of cellulose. Combined experiments, density functional theory calculations, and molecular dynamic simulations were performed. The type and amount of co-solvent were found to have a significant impact on the solubility of cellulose, the dissolution process, and the structure of regenerated cellulose. The addition of organic solvents can significantly reduce the cellulose dissolution temperature and increase the solubility. Among the solvents assessed, 40 wt% DMSO exhibited the most effective synergistic interaction with SIL, where the solubility of cellulose was 14.6 wt% at 75 °C. Subsequently, the effects of the different types and amounts of co-solvents on the microscopic morphology and chemical structure of regenerated cellulose were thoroughly explored. The results showed that different types of organic solvents had different effects on the microstructure of regenerated cellulose. The results may guide the manufacturing specifications of high-performance regenerated fiber materials.
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2
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Glycosidic bond protection of cellulose during solvent dissolution by coordination interaction competition strategy. Carbohydr Polym 2024; 328:121665. [PMID: 38220316 DOI: 10.1016/j.carbpol.2023.121665] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/27/2023] [Revised: 11/11/2023] [Accepted: 12/03/2023] [Indexed: 01/16/2024]
Abstract
Exploiting new solvents on efficiently dissolving cellulose is imperative to promote the utilization of cellulosic resources. The process of cellulose dissolution typically necessitates extreme conditions, such as high-temperature treatment, utilization of potent acidic or basic solvents, or the catalytic action of Lewis acids. As a result, the structure of the cellulose is invariably compromised, subsequently obstructing the creation of high-performance materials. In this study, we address this challenge through a simple process, introducing polyethylene glycol (PEG) as glycosidic bond protecting agent, to preserve the polymerization degree of cellulose during its room-temperature dissolution in ZnCl2-phosporic acid eutectic solvent. The PEG units preferentially coordinate with Zn2+ to weaken the hydrolysis of glycosidic bond of cellulose through ether bond competition. The polymerization degree of regenerated cellulose is thus greatly improved, reaching up to seven times that of unprotected cellulose. Overall, this study offers an easy and cost-effective approach to develop cellulose solvents and provides a significant drive towards the fabrication of practical materials through cellulose dissolution.
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3
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Cellulose dissolution and regeneration behavior via DBU-levulinic acid solvents. Int J Biol Macromol 2023; 252:126548. [PMID: 37648138 DOI: 10.1016/j.ijbiomac.2023.126548] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/15/2023] [Revised: 07/22/2023] [Accepted: 08/24/2023] [Indexed: 09/01/2023]
Abstract
Most organic solvents are unable to dissolve carbohydrates due to the lack of hydrogen bonding ability. The development of solvent systems for dissolving cellulose is of great importance for its utilization and conversion. In this study, four new cellulose solvents were designed using inexpensive levulinic acid (LevA) and 1,8-diazabicyclo [5,4,0] undec-7-ene (DBU) as raw materials. The results showed that the prepared DBU-LevA-2 solvent was able to dissolve up to 7 wt% of bamboo cellulose (DP = 860) and 16 wt% of microcrystalline cellulose (DP = 280) at 100 °C and regenerated without derivatization. Also, the molar ratio of each component of this solvent has a significant effect on the dissolution properties of cellulose. The regenerated cellulose had the typical crystalline characteristics of cellulose II. Subsequently, the interactions and microscopic behaviors of solvent and cellulose during the dissolution process were thoroughly investigated by using NMR spectroscopy combined with density functional theory. The systematic study showed that the hydrogen bond-forming ability provided by DBU, a superbase, plays an indispensable role in the overall solvent system.
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Dissolution of lignocellulose with high lignin content in AlCl 3/ZnCl 2 aqueous system and properties of the regenerated cellulose film. Int J Biol Macromol 2023; 234:123590. [PMID: 36773876 DOI: 10.1016/j.ijbiomac.2023.123590] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/11/2022] [Revised: 01/20/2023] [Accepted: 02/05/2023] [Indexed: 02/11/2023]
Abstract
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.
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Probing cellulose-solvent interactions with self-diffusion NMR: Onium hydroxide concentration and co-solvent effects. Carbohydr Polym 2023; 303:120440. [PMID: 36657835 DOI: 10.1016/j.carbpol.2022.120440] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/01/2022] [Revised: 11/30/2022] [Accepted: 12/04/2022] [Indexed: 12/14/2022]
Abstract
The molecular self-diffusion coefficients were accessed, for the first time, in solutions of microcrystalline cellulose, dissolved in 30 wt% and 55 wt% aqueous tetrabutylammonium hydroxide, TBAH (aq), and in mixtures of 40 wt% TBAH (aq) with an organic co-solvent, dimethylsulfoxide (DMSO), through pulsed field gradient stimulated echo NMR measurements. A two-state model was applied to estimate α (i.e., average number of ions that "bind" to each anhydroglucose unit) and Pb (i.e., fraction of "bound" molecules of DMSO, TBAH or H2O to cellulose) parameters. The α values suggest that TBA+ ions can bind to cellulose within 0.5 TBA+ to 2.3 TBA+/AGU. On the other hand, the Pb parameter increases when raising cellulose concentration for TBA+, DMSO and water in all solvent systems. Data suggests that TBAH interacts with the ionized OH groups from cellulose forming a sheath of bulky TBA+ counterions which consequently leads to steric hindrance between cellulose chains.
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High-tensile regenerated cellulose films enabled by unexpected enhancement of cellulose dissolution in cryogenic aqueous phosphoric acid. Carbohydr Polym 2022; 277:118878. [PMID: 34893281 DOI: 10.1016/j.carbpol.2021.118878] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/19/2021] [Revised: 11/05/2021] [Accepted: 11/07/2021] [Indexed: 11/15/2022]
Abstract
We have demonstrated, for the first time, high-efficient non-destructive and non-derivative dissolution of cellulose could be achieved in cryogenic aqueous phosphoric acid. Cellulose from different sources and of varying degree of polymerization from 200 (MCC) to 2200 (cotton fabric) could be dissolved completely to afford solutions containing 5 wt%-18 wt% cellulose, from which ultra-strong and tough cellulose films of tensile strength as high as 707 MPa could be obtained using water as the coagulant. These solutions can be stored at -18 °C for extended time without noticeable degradation while desired degree of polymerization is also attainable by tuning the storage conditions. The findings of this work call for renewal attention on phosphoric acid as a promising cellulose solvent for being non-toxic, non-volatile, easy to handle, and cost-effective.
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Dissolution behavior of cellulose in a novel cellulose solvent. Carbohydr Res 2021; 511:108490. [PMID: 34952277 DOI: 10.1016/j.carres.2021.108490] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/11/2021] [Revised: 12/12/2021] [Accepted: 12/13/2021] [Indexed: 11/02/2022]
Abstract
We have found that cellulose can be dissolved rapidly in the mixed solvent of tetrabutylammonium acetate (TBAA) and a polar aprotic solvents (PAS) at 50 °C and the obtained cellulose solution could be regenerated into cellulose film and fiber. The factors affecting the dissolution behavior of cellulose were investigated and it was found that the solubility and dissolution rate of cellulose in the mixed solvent are significantly dependent on the species of PAS and the molar ratio of PAS/TBAA. The suitable PAS are dimethyl sulfoxide, pyridine, dimethylacetamide, dimethylformamide and N-Methyl-2-pyrrolidone, and dimethyl sulfoxide is the best one in regard to the solubility and dissolution rate of cellulose. The optimal molar ratio of PAS/TBAA was determined by DN of the polar aprotic solvents. The dissolution behaviour of cellulose in the mixed solvent was proposed to involve the solvent diffusion, solvation of TBA+ as well as disruption of the intermolecular or intramolecular hydrogen bonds of cellulose.
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8
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Robust superbase-based emerging solvents for highly efficient dissolution of cellulose. Carbohydr Polym 2021; 272:118454. [PMID: 34420714 DOI: 10.1016/j.carbpol.2021.118454] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/02/2021] [Revised: 07/07/2021] [Accepted: 07/11/2021] [Indexed: 11/23/2022]
Abstract
The development of robust solvent systems for cellulose dissolution is of significant importance for cellulose utilization and transformation. Herein, six kinds of novel superbase-based solvents were designed by a combination of 1,5-diazabicyclo[4.3.0]non-5-ene (DBN) with pyridine N-oxide (PyO) or 2-picoline-N-oxide (PiO) for dissolution of cellulose. It was observed that the prepared superbase-based solvents (denoted as DBN-PyO-x and DBN-PiO-4) could efficiently dissolve cellulose at mild temperatures (<80 °C). The chemical structure of the prepared superbase-based solvents and the molar ratio of the components significantly affected the solubility of cellulose, and DBN-PyO-4 showed the best performance with a cellulose solubility of 14.1 wt% 70 °C. The systematic study revealed that the good performance of the prepared superbase-based solvents on cellulose dissolution resulted from the synergistic effect of their ability to form hydrogen bonds and their polarizability.
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Mesoporous cellulose-chitosan composite hydrogel fabricated via the co-dissolution-regeneration process as biosorbent of heavy metals. ENVIRONMENTAL POLLUTION (BARKING, ESSEX : 1987) 2021; 286:117324. [PMID: 33990049 DOI: 10.1016/j.envpol.2021.117324] [Citation(s) in RCA: 12] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/09/2020] [Revised: 04/18/2021] [Accepted: 05/04/2021] [Indexed: 06/12/2023]
Abstract
Developing low-cost and high-performance biosorbent for water purification continues drawing more and more attention. In this study, cellulose-chitosan composite hydrogels were fabricated via a co-dissolution and regeneration process using a molten salt hydrate (a 60 wt% aqueous solution of LiBr) as a solvent. The addition of chitosan not only introduced functionality for metal adsorption but also increased the specific surface area and improved the mechanical strength of the composite hydrogel, compared to pure cellulose hydrogel. Batch adsorption experiments indicated that the composite hydrogel with 37% cellulose and 63% chitosan exhibited an adsorption capacity of 94.3 mg/g (1.49 mmol/g) toward Cu2+ at 23 °C, pH 5, and initial metal concentration of 1500 mg/L, which was 10 times greater than the adsorption capacity of pure cellulose hydrogel. Competitive adsorption from a mixed metals solution revealed that the cellulose-chitosan composite hydrogel exhibited selective adsorption of the metals in the order of Cu2+ > Zn2+ > Co2+. This study successfully demonstrated an innovative method to fabricate biosorbents from abundant and renewable natural polymers (cellulose and chitosan) for removing metal ions from water.
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Polar zwitterion/saccharide-based deep eutectic solvents for cellulose processing. Carbohydr Polym 2021; 267:118171. [PMID: 34119143 DOI: 10.1016/j.carbpol.2021.118171] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/19/2021] [Revised: 04/16/2021] [Accepted: 05/01/2021] [Indexed: 11/18/2022]
Abstract
Liquid zwitterions are biocompatible cellulose solvents and have enabled successive ethanol production from plant biomass in the same reaction pot. However, only a few carboxylate-type liquid zwitterions have been reported since almost all zwitterions are solid. Here, we propose zwitterion-based deep eutectic solvents (DESs) to expand the choices of zwitterionic solvents for cellulose dissolution and the subsequent processing. Zwitterion-based DESs were prepared by mixing four types of saccharide at various ratios. Twenty-two combinations of zwitterion/saccharide mixtures formed DESs, that is, liquid state below 100 °C. Two of them, whose saccharide ratio were 5 wt%, successfully dissolved cellulose because the low saccharide load was sufficient for liquefaction but did not disrupt the intrinsic cellulose dissolution ability of zwitterions.
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A study elucidating the relation between cellulose dissolution and crystallinity after cellulase treatment at different doses. 3 Biotech 2021; 11:371. [PMID: 34295611 DOI: 10.1007/s13205-021-02920-7] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/23/2021] [Accepted: 07/08/2021] [Indexed: 10/20/2022] Open
Abstract
Cellulose is the most abundant renewable resource which has found a diverse range of applications. Cellulose dissolution is a significant property for manufacturing man-made cellulosic fiber through viscose process. Crystalline microfibrillar structure and relatively high ordered packing of polymeric chains contribute to recalcitrance and poor reactivity of cellulose. One of the most common methods to improve cellulose dissolution is cellulase treatment. Herein, cellulase treatment at different doses was studied to explore the correlation of cellulose dissolution with crystallinity. Pulp showed improvement in Fock reactivity and other properties related to viscose application. But contrary to previous studies, cellulose crystallinity as determined by XRD and FTIR did not correlate with Fock reactivity at a higher dose of cellulase. The results indicated some complex mechanism to be involved between the cellulose dissolution and crystallinity than a simple negative correlation. Cellulase treatment at 150 HCU/g resulted in the upgraded pulp suitable for viscose application.
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Designing cellulose hydrogels from non-woody biomass. Carbohydr Polym 2021; 264:118036. [PMID: 33910744 DOI: 10.1016/j.carbpol.2021.118036] [Citation(s) in RCA: 22] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/01/2021] [Revised: 03/28/2021] [Accepted: 03/30/2021] [Indexed: 01/20/2023]
Abstract
Hydrogels are an attractive system for a myriad of applications. While most hydrogels are usually formed from synthetic materials, lignocellulosic biomass appears as a sustainable alternative for hydrogel development. The valorization of biomass, especially the non-woody biomass to meet the growing demand of the substitution of synthetics and to leverage its benefits for cellulose hydrogel fabrication is attractive. This review aims to present an overview of advances in hydrogel development from non-woody biomass, especially using native cellulose. The review will cover the overall process from cellulose depolymerization, dissolution to crosslinking reaction and the related mechanisms where known. Hydrogel design is heavily affected by the cellulose solubility, crosslinking method and the related processing conditions apart from biomass type and cellulose purity. Hence, the important parameters for rational designs of hydrogels with desired properties, particularly porosity, transparency and swelling characteristics will be discussed. Current challenges and future perspectives will also be highlighted.
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Revisiting the dissolution of cellulose in H 3PO 4(aq) through cryo-TEM, PTssNMR and DWS. Carbohydr Polym 2020; 252:117122. [PMID: 33183588 DOI: 10.1016/j.carbpol.2020.117122] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/25/2020] [Revised: 07/06/2020] [Accepted: 09/15/2020] [Indexed: 10/23/2022]
Abstract
Cellulose can be dissolved in concentrated acidic aqueous solvents forming extremely viscous solutions, and, in some cases, liquid crystalline phases. In this work, the concentrated phosphoric acid aqueous solvent is revisited implementing a set of advanced techniques, such as cryo-transmission electronic microscopy (cryo-TEM), polarization transfer solid-state nuclear magnetic resonance (PTssNMR), and diffusing wave spectroscopy (DWS). Cryo-TEM images confirm that this solvent system is capable to efficiently dissolve cellulose. No cellulose particles, fibrils, or aggregates are visible. Conversely, PTssNMR revealed a dominant CP signal at 25 °C, characteristic of C-H bond reorientation with correlation time longer than 100 ns and/or order parameter above 0.5, which was ascribed to a transient gel-like network or an anisotropic liquid crystalline phase. Increasing the temperature leads to a gradual transition from CP to INEPT-dominant signal and a loss of birefringence in optical microscopy, suggesting an anisotropic-to-isotropic phase transition. Finally, an excellent agreement between optical microrheology and conventional mechanical rheometry was also obtained.
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Highly efficient cellulose dissolution by alkaline ionic liquids. Carbohydr Polym 2019; 229:115594. [PMID: 31826468 DOI: 10.1016/j.carbpol.2019.115594] [Citation(s) in RCA: 17] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/11/2019] [Revised: 11/05/2019] [Accepted: 11/09/2019] [Indexed: 11/30/2022]
Abstract
Alkaline ionic liquids (ILs) with unconventional organic anions were prepared and used for cellulose dissolution studies. High concentrations of cellulose were dissolved at room temperature in the phenolate based imidazolium IL [C2mim][OPh], combined with organic solvent, and up to 45 wt-% cellulose dissolution (wt-% MCC of weight IL) was readily achieved at 100 ºC. No functionalization of the regenerated cellulose was observed during the dissolution process (FTIR). Characteristic cellulose II XRD diffraction pattern was observed after IL dissolution and regeneration of MCC. The crystallinity index (CI) of the pretreated MCC was reduced from 93.2 % to 31 %. Inert conditions were not required for the cellulose dissolution experiments. This study indicates that the IL H-bond basicity is not the only key parameter determining their cellulose dissolution ability. The alkaline ILs represent an energy efficient and sustainable approach for cellulose dissolution.
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Binary mixtures of ionic liquids-DMSO as solvents for the dissolution and derivatization of cellulose: Effects of alkyl and alkoxy side chains. Carbohydr Polym 2019; 212:206-214. [PMID: 30832848 DOI: 10.1016/j.carbpol.2019.02.024] [Citation(s) in RCA: 23] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/04/2018] [Revised: 02/04/2019] [Accepted: 02/08/2019] [Indexed: 11/19/2022]
Abstract
The efficiency of mixtures of ionic liquids (ILs) and molecular solvents in cellulose dissolution and derivatization depends on the structures of both components. We investigated the ILs 1-(1-butyl)-3-methylimidazolium acetate (C4MeImAc) and 1-(2-methoxyethyl)-3-methylimidazolium acetate (C3OMeImAc) and their solutions in dimethyl sulfoxide, DMSO, to assess the effect of presence of an ether linkage in the IL side-chain. Surprisingly, C4MeImAc-DMSO was more efficient than C3OMeImAc-DMSO for the dissolution and acylation of cellulose. We investigated both solvents using rheology, NMR spectroscopy, and solvatochromism. Mixtures of C3OMeImAc-DMSO are more viscous, less basic, and form weaker hydrogen bonds with cellobiose than C4MeImAc-DMSO. We attribute the lower efficiency of C3OMeImAc to "deactivation" of the ether oxygen and C2H of the imidazolium ring due to intramolecular hydrogen bonding. Using the corresponding ILs with C2CH3 instead of C2H, namely, 1-butyl-2,3-dimethylimidazolium acetate (C4Me2ImAc) and 1-(2-methoxyethyl)-2,3-dimethylimidazolium acetate (C3OMe2ImAc) increased the concentration of dissolved cellulose; without noticeable effect on biopolymer reactivity.
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Brief overview on cellulose dissolution/regeneration interactions and mechanisms. Adv Colloid Interface Sci 2015; 222:502-8. [PMID: 24931119 DOI: 10.1016/j.cis.2014.05.004] [Citation(s) in RCA: 201] [Impact Index Per Article: 22.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/07/2014] [Revised: 05/07/2014] [Accepted: 05/12/2014] [Indexed: 11/29/2022]
Abstract
The development of cellulose dissolution/regeneration strategies constitutes an increasingly active research field. These are fundamental aspects of many production processes and applications. A wide variety of suitable solvents for cellulose is already available. Nevertheless, most solvent systems have important limitations, and there is an intense activity in both industrial and academic research aiming to optimize existing solvents and develop new ones. Cellulose solvents are of highly different nature giving great challenges in the understanding of the subtle balance between the different interactions. Here, we briefly review the cellulose dissolution and regeneration mechanisms for some selected solvents. Insolubility is often attributed to strong intermolecular hydrogen bonding between cellulose molecules. However, recent work rather emphasizes the role of cellulose charge and the concomitant ion entropy effects, as well as hydrophobic interactions.
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