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Structure characterization of the regenerated cellulose by water, methanol, ethanol and n-propanol: a XRD patterns, b CP MAS ¹³C NMR spectra, c/d FT-IR spectra and e/f second derivative IR spectra
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![Chemical structure of a cellulose and b [Bmim]Cl](publication/325630183/figure/fig1/AS:941544844574764@1601493192549/Chemical-structure-of-a-cellulose-and-b-BmimCl_Q320.jpg)
In this work, cellulose nanoparticles regenerated by water, methanol, ethanol and n-propanol as the anti-solvents from ionic liquid solution were studied systematically. Crystallinity and enthalpy in cellulose degradation of the regenerated cellulose decreased in the order water > methanol > ethanol > n-propanol. Nevertheless, the thermal stability...
Citations
... were denoted as CMS-X-Pd. During the dissolving process of MCC, the anion of OAc À in EmimOAc and Pd(OAc) 2 can disrupt the hydrogen bonds within cellulose, 30 and strongly interact with the hydroxyl groups of cellulose. 31 Therefore, Pd 2+ gradually coordinated with the cellulose molecular chains, 32 as illustrated in Figure 1A. ...
Blue hydrogen produced from fossil fuels is recognized as a promising large‐scale technology for realizing the hydrogen economy. Membrane‐based separation is emerging as a viable alternative to traditional hydrogen purification technologies. Here, we present a facile strategy for fabricating carbon molecular sieve (CMS) hollow fiber membranes containing uniformly dispersed palladium (Pd) nanoparticles. The Pd nanoparticles, anchored in the carbon strands of CMS membranes, induced the carbon matrix toward a more ordered structure arrangement through a synergistic effect of entropy‐driven size exclusion and acceleration of graphitization. As a result, the doped Pd nanoparticles facilitated the formation of ultramicropores <3.3 Å in the CMS membranes, which enabled a precise molecular sieving ability between H2 and CO2 with H2/CO2 selectivity up to 247. Furthermore, the membrane presented good mixed gas separation performances and was stable for over 250 h under simulated harsh industrial conditions.
... While the mechanism of cellulose dissolution has been systematically investigated [117], cellulose regeneration phenomenon is inherently difficult to study. Zhou et al. [118] investigated the effect of different antisolvents on the regeneration from MCC/BmimCl solution using ATR-FTIR. The H-bond interaction between the chlorine ion and antisolvents is the driving force for cellulose regeneration. ...
This review summarizes the recent advances in preparing cellulose hydrogels via ionic liquid-based processes and the applications of regenerated cellulose hydrogels/iongels in electrochemical materials, separation membranes, and 3D printing bioinks. Cellulose is the most abundant natural polymer, which has attracted great attention due to the demand for eco-friendly and sustainable materials. The sustainability of cellulose products also depends on the selection of the dissolution solvent. The current state of knowledge in cellulose preparation, performed by directly dissolving in ionic liquids and then regenerating in antisolvents, as described in this review, provides innovative ideas from the new findings presented in recent research papers and with the perspective of the current challenges.
... For this reason, the effect of non-solvent on the rheological properties of a cellulose solution and indirectly its phase state was studied in the absence of DMSO to have a possibility for varying the mass fraction of non-solvent more significantly and also to avoid a specific DMSO/non-solvent interaction. Water, methanol, ethanol, and isopropanol were used as non-solvents, assuming a decrease in the ability to be a proton donor (i.e., to initiate hydrogen bonds) in the designated series (the Kamlet-Taft solvatochromic parameter α that characterizes H-bond donation is 1.17, 0.98, 0.86, and 0.76, respectively [84,85]). ...
The weak point of ionic liquids is their high viscosity, limiting the maximum polymer concentration in the forming solutions. A low-viscous co-solvent can reduce viscosity, but cellulose has none. This study demonstrates that dimethyl sulfoxide (DMSO), being non-solvent for cellulose, can act as a nominal co-solvent to improve its processing into a nanofiltration membrane by phase inversion. A study of the rheology of cellulose solutions in diluted ionic liquids ([EMIM]Ac, [EMIM]Cl, and [BMIM]Ac) containing up to 75% DMSO showed the possibility of decreasing the viscosity by up to 50 times while keeping the same cellulose concentration. Surprisingly, typical cellulose non-solvents (water, methanol, ethanol, and isopropanol) behave similarly, reducing the viscosity at low doses but causing structuring of the cellulose solution and its phase separation at high concentrations. According to laser interferometry, the nature of these non-solvents affects the mass transfer direction relative to the forming membrane and the substance interdiffusion rate, which increases by four-fold when passing from isopropanol to methanol or water. Examination of the nanofiltration characteristics of the obtained membranes showed that the dilution of ionic liquid enhances the rejection without changing the permeability, while the transition to alcohols increases the permeability while maintaining the rejection.
... The fundamental mechanism of cellulose dissolving was determined to be the anion's basicity, [129] which destroys the hydrogen bonds in cellulose. The potentiality of cellulose solvents discovered that the [C2mim]OAc had some promising qualities because the acetate salt has a lower melting point, lower toxicity, and higher cellulose dissolution ability [130]. The biodegradability was clearly enhanced. ...
The latest advancements in cellulose and its derivatives are the subject of this study. We summarize the characteristics, modifications, applications, and properties of cellulose. Here, we discuss new breakthroughs in modified cellulose that allow for enhanced control. In addition to standard approaches, improvements in different techniques employed for cellulose and its derivatives are the subject of this review. The various strategies for synthetic polymers are also discussed. The recent advancements in polymer production allow for more precise control, and make it possible to make functional celluloses with better physical qualities. For sustainability and environmental preservation, the development of cellulose green processing is the most abundant renewable substance in nature. The discovery of cellulose disintegration opens up new possibilities for sustainable techniques. Based on the review of recent scientific literature, we believe that additional chemical units of cellulose solubility should be used. This evaluation will evaluate the sustainability of biomass and processing the greenness for the long term. It appears not only crucial to dissolution, but also to the greenness of any process.
... A possible strategy for reducing the size of CMGs (and thus improving the stability of the emulsions) is to disrupt or delay the reformation of inter-and intramolecular H-bonds during coagulation, allowing formation of smaller particles [38]. Agitation of the coagulating solution also leads to a significant difference in crystallinity of the reprecipitated cellulose [39,40], which may make it easier to disperse and may improve the cellulose surface properties. ...
Soluble polysaccharides have been used extensively as gelling/thickening agents in emulsions, but they generally display weak surface activity. Insoluble polysaccharides such as cellulose can be converted to thickening agents and even emulsifiers, but generally only after considerable chemical modification. Here we use the ionic liquid (IL) 1-butyl-3-methyl imidazolium acetate (BmimAc) to dissolve and reprecipitate cellulose in the presence of oil, i.e., a physical process, to tune the cellulose properties. ILs have previously been used in this way to form hydrophobic (‘oily’) cellulose microgels (CMGs), potentially capable of stabilizing water-in-oil (W/O) emulsions. However, these previous CMGs were made via a ‘top-down’ method and were relatively large and polydisperse, giving limited stability to the W/O emulsions formed. Here we demonstrate how the CMG size can be drastically reduced via a ‘bottom-up’ approach and employing high-pressure homogenization (HPH), thus achieving sub-micron CMG particle sizes. This has previously been impossible with other reported IL-cellulose coagulation methods and the corresponding W/O emulsions were more stable. In addition, confocal and cryo-scanning electron microscopy (SEM) revealed that the surface coverage of these CMGs on droplets increased over time, which led to the formation of even thicker interfacial layers and further enhanced emulsion stability (at least 2 months). We also demonstrate unequivocally that the stability of the W/O emulsions is indeed due to the CMGs adsorbing via the Pickering mechanism, rather than forming a stabilizing cellulosic network in the continuous phase, thus providing a novel route to ‘green’ Pickering emulsions.
... Two geometrical criteria were defined for the H-bonds: (1) the distance of the donor-acceptor is ≤3.5 Å, and (2) the angle of the hydrogen donor-acceptor is less than 30 • (the deviation of the OH from the O-O internuclear axis) [43,44]. The H-bonds' networks of cellulose are important standards against which to measure its regeneration [45]. To investigate the role of anti-solvents, the number of H-bonds between cellulose chains over 50-100 ns are collected in Figure 3. ...
The experiments on cellulose dissolution/regeneration have made some achievements to some extent, but the mechanism of cellulose regeneration in ionic liquids (ILs) and anti-solvent mixtures remains elusive. In this work, the cellulose regeneration mechanism in different anti-solvents, and at different temperatures and concentrations, has been studied with molecular dynamics (MD) simulations. The IL considered is 1-ethyl-3-methylimidazolium acetate (EmimOAc). In addition, to investigate the microcosmic effects of ILs and anti-solvents, EmimOAc-nH2O (n = 0–6) clusters have been optimized by Density Functional Theory (DFT) calculations. It can be found that water is beneficial to the regeneration of cellulose due to its strong polarity. The interactions between ILs and cellulose will become strong with the increase in temperature. The H-bonds of cellulose chains would increase with the rising concentrations of anti-solvents. The interaction energies between cellulose and the anions of ILs are stronger than that of cations. Furthermore, the anti-solvents possess a strong affinity for ILs, cation–anion pairs are dissociated to form H-bonds with anti-solvents, and the H-bonds between cellulose and ILs are destroyed to promote cellulose regeneration.
... Regarding the parameters that influence this process, the H-bond acidity of the antisolvent has been shown to affect the regeneration of pure cellulose from ILs. When comparing different antisolvents, namely water, methanol, ethanol, and n-propanol, Fan et al. [186] reported the favoured regeneration of this polysaccharide (dissolved in [Bmim]Cl) in water, since water possessed the highest H-bond acidity. The choice of the antisolvent also influenced the properties of the regenerated cellulose nanoparticles, namely the crystallinity, enthalpy in cellulose degradation, and thermal stability [186]. ...
... When comparing different antisolvents, namely water, methanol, ethanol, and n-propanol, Fan et al. [186] reported the favoured regeneration of this polysaccharide (dissolved in [Bmim]Cl) in water, since water possessed the highest H-bond acidity. The choice of the antisolvent also influenced the properties of the regenerated cellulose nanoparticles, namely the crystallinity, enthalpy in cellulose degradation, and thermal stability [186]. ...
Cellulose, the most abundant natural polymer, is a versatile polysaccharide that is being exploited to manufacture innovative blends, composites, and hybrid materials in the form of membranes, films, coatings, hydrogels, and foams, as well as particles at the micro and nano scales. The application fields of cellulose micro and nanoparticles run the gamut from medicine, biology, and environment to electronics and energy. In fact, the number of studies dealing with sphere-shaped micro and nanoparticles based exclusively on cellulose (or its derivatives) or cellulose in combination with other molecules and macromolecules has been steadily increasing in the last five years. Hence, there is a clear need for an up-to-date narrative that gathers the latest advances on this research topic. So, the aim of this review is to portray some of the most recent and relevant developments on the use of cellulose to produce spherical micro- and nano-sized particles. An attempt was made to illustrate the present state of affairs in terms of the go-to strategies (e.g., emulsification processes, nanoprecipitation, microfluidics, and other assembly approaches) for the generation of sphere-shaped particles of cellulose and derivatives thereof. A concise description of the application fields of these cellulose-based spherical micro and nanoparticles is also presented.
... MCC), whilst addition of alcohols leads to a larger decrease in crystallinity and an increase in amorphous cellulose (Xu et al. 2008;Lan et al. 2011;Ö stlund et al. 2013;Sun et al. 2015;Zhang et al. 2018). For example, cellulose dissolved in EmimAc was regenerated separately in water and ethanol, giving degrees of crystallinity of 43.33% and 13.45% respectively (Tan et al. 2019), whilst similar observations were made for CNPs regenerated in water, methanol, ethanol and n-propanol (43.9%, 26.9%, 20.3% and 12.5% respectively) (Fan et al. 2018). In all of these examples, the coagulated material consisted of cellulose particles. ...
... For example, cellulose gels and CNPs regenerated using the same four anti-solvents displayed the opposite trend in crystallinity. As described above (Fan et al. 2018), the crystallinity of the CNPs decreases as the polarity of the anti-solvent decreases, but crystallinity decreased in the following order for cellulose gels: npropanol [ ethanol [ methanol [ water (Fan et al. 2017). Such a different result is believed to be governed by the diffusion coefficient (D) of the various anti-solvent molecules. ...
... On the other hand, regeneration with high enough stirring generates cellulose particles in which the anti-solvent H-bonding properties dictate the crystallinity of the regenerated cellulose. Thus two competitive mechanisms can take place during regeneration (Fan et al. 2018). It is also important to mention that cellulose gels will only form when the concentration of dissolved cellulose is sufficiently high, in order for the reprecipitating material to be able to form a network structure. ...
Microgel particles have recently emerged as an alternative route to emulsion stabilisation. Classed as soft colloidal particles, their ability to swell to differing degrees in certain solvents and to rearrange once attached to an interface makes them highly suitable for systems requiring long-term stabilization, such as formulations in the food, agricultural, cosmetic and pharmaceutical industries. Microgels made with biocompatible polymers such as proteins and polysaccharides in particular offer an environmental advantage and currently form a very active area of research. Cellulose, being a natural, biodegradable polymer, is an attractive ingredient for gels and microgels. However, its use as a functional material is often somewhat hindered by its insolubility in water and most other organic solvents. Furthermore, the surface activity of cellulose has proven difficult to harness and therefore its ability to act as an emulsion stabiliser has been almost exclusively applied to oil-in-water (O/W) emulsions, with very few reports on its water in oil (W/O) activity. This review aims to summarise some of the recent progress made in the microgel field including their ability to act as emulsion stabilisers, with a focus on cellulose microgels (CMGs). A brief overview of cellulose processing is also given, describing the dissolution and reprecipitation routes used to functionalise cellulose without covalent modification and the potential for cellulose particles and CMGs to act as O/W and W/O emulsion stabilisers.
Graphic abstract
... In 2002, Rogers and coworkers initiated the research on developing ILs as cellulose dissolving solvent began in 2002 by Rogers' group (Swatloski, Spear, Holbrey, & Rogers, 2002). Due to its multidirectional merits, such as thermal and chemical stability, negligible volatility, flame retardancy, and reusability (Armand, Endres, MacFarlane, Ohno, & Scrosati, 2009), researchers contributed enormous efforts to explore its dissolving mechanism (Brandt, Hallett, Leak, Murphy, & Welton, 2010;Endo, Hosomi, Fujii, Ninomiya, & Takahashi, 2016;Jiang et al., 2017;Li, Wang, Liu, & Zhang, 2018;Remsing, Swatloski, Rogers, & Moyna, 2006), by preparing cellulose-based materials (Liu et al., 2012Wan, Zhang, Yu, & Zhang, 2017;Wang et al., 2017;Zhang et al., 2007), and studying the cellulose regeneration details from ILs (Fan et al., 2018;Fan, Xie, Chen, Sun, & Zhou, 2019;Gupta, Hu, & Jiang, 2013;Lindman et al., 2017;Rabideau & Ismail, 2015). ...
... The crystallinity of cellulose fibers was calculated based on NMR and XRD data. For NMR, the signal of C4 was used for peak fitting (Fan et al., 2018). The crystallinity was 8 % and 11 % for the regenerated cellulose that was from IL-Cell solution and Cu 2+ & IL-Cell solution, respectively. ...
The high viscosity of ionic liquids, even at relatively high temperatures, can greatly affect the production of cellulose fibers through the wet-spinning process. The high viscosity mainly by due to the hydrogen bond interaction between the cations and anions of ionic liquids. It is possible to reduce the viscosity by modulating the hydrogen bond interaction. In the present work, copper chloride (CuCl2) was dissolved in 1-butyl-3-methylimidazolium chloride ([Bmim]Cl)-cellulose solution, followed by the formation of a complex with the chloride anions by converting it to [CuCl4]²⁻ anion. Through this strategy, the extrusion velocity of the solution improved, and the produced fibers obtained smoother surfaces and shrunken diameters.
... Once dissolved in an IL, cellulose can be recovered by adding a socalled 'coagulant' or 'anti-solvent,' such as water, ethanol or n-propanol, which is miscible with the IL but not with cellulose (Tan, Chen, Li, & Xie, 2019). Varying the coagulation conditions, as well as the type and amount of anti-solvent, yields cellulose in different forms and allows manipulation of its properties (Fan et al., 2018;Gupta, Hu, & Jiang, 2013;Tan et al., 2019). Thorough washing of the regenerated cellulose also completely removes any IL, permitting recovery of the IL and anti-solvents and ensuring that the resultant cellulose is pure and safe for consumption. ...
Non-derivatised cellulose is generally assumed to have poor surface activity and therefore be unsuitable as a water in oil (W/O) emulsifier. In this work, a “natural” cellulose microgel (CMG) is fabricated via a top-down approach and used to stabilize W/O emulsions, without employing chemical modification. The cellulose is coagulated from an ionic liquid through a solvent-exchange process, in the presence and absence of added sunflower oil, in order to tune the cellulose morphology and properties. Detailed characterization of the nature of these microgels and the effect of the solvent change sequence on their emulsifying properties was investigated. In the presence of oil, Fourier transform infrared (FTIR) spectroscopy confirmed the retention of oil in the coagulum during regeneration and the resultant CMGs were more easily dispersed in oil than water, suggesting the fabrication of a “hydrophobic” microgel. Confocal microscopy confirmed the adsorption of CMGs to the water-oil interface and W/O emulsions of up to 20 vol% water displayed good stability over at least 1 month. This study therefore describes a “novel” route to W/O stabilization using a natural emulsifier, which could be then used as a method of reducing fat and sugar in food products.
