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Views of the cellulose I crystal packing with the (1 f 4) linkage directed out of the page for (a) parallel down and (b) parallel up packing.
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The crystal structure of Valonia cellulose I is determined by X-ray fiber diffraction analysis. A careful reanalysis of two existing X-ray diffraction data sets for Valonia cellulose I leads to a consistent, definitive structure of the -phase. The results resolve ambiguities in existing X-ray analyses between "parallel up" and "parallel down" packi...
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Context 1
... interesting question is "why does cellulose pack in the parallel up, rather than the parallel down, arrangement"? Parts a and b of Figure 2 show the parallel up and parallel down packing, respectively, displayed such that the polarities of the molecular chains are the same. Defining the unit cells this way means that γ ≈ 83° and γ ≈ 97° in parts a and b, respectively ( Figure 2). ...
Context 2
... a and b of Figure 2 show the parallel up and parallel down packing, respectively, displayed such that the polarities of the molecular chains are the same. Defining the unit cells this way means that γ ≈ 83° and γ ≈ 97° in parts a and b, respectively ( Figure 2). Hence, relative to the molecules, parallel down and parallel up packings correspond to γ ≈ 83° and γ ≈ 97°, respectively. ...
Context 3
... question posed above can then be recast as "why does cellulose pack with γ ≈ 97° rather than γ ≈ 83°"? Or more generally as "why does cellulose pack with γ ≈ 97°, rather than some other value of γ"? Referring to Figure 2, what γ determines, together with w, is the relative position with which the two sheets of cellulose molecules pack. Two calculations were made to shed some light on the answer to this question. ...
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... To study the effects of different silane coupling agents that modify cellulose and different concentrations of KH1631, molecular dynamics simulations (MS) were conducted with Materials Studio 6.0 using the COMPASS Force Field. A Nosé-Hoover thermostat was used to maintain the temperature at 298 K and 405 K. MS first involved geometric optimization of silane coupling agent chain and cellulose crystal models (Finkenstadt and Millane 1998), after which dynamic analysis was carried out. ...
With the increasing demand for environmentally friendly and sustainable materials, research on cellulose/bio-based polyester composites has received increasing attention. However, the hydrophilicity of cellulose remains a major factor in its poor interaction with hydrophobic bio-based polyester. To prepare microcrystalline cellulose (MCC)/poly(butylene succinate) (PBS) composite monofilaments with high cellulose content to suppress the deformation of PBS, hexadecyltrimethoxysilane (KH1631) was selected for surface silylation of MCC at a mass ratio of 1:0.5 based on the principle of polarity similarity. The physical–chemical double crosslinking of KH1631 with MCC enhanced the interfacial bonding between MCC and PBS, so composite monofilaments with modified MCC (named mMCC) contents up to 35 wt% were prepared by melt spinning. After thermal stretching, mMCC/PBS composite monofilaments exhibited uniformly distributed microporous structure and double yield behaviors. Despite the continuous decrease in breaking strength (from 210 to 84 MPa) and elastic modulus (from 1380 to 590 MPa) due to the addition of mMCC, the yield strength (116 MPa) of the mMCC/PBS composite monofilaments was consistent with that of PBS when the mMCC addition reached 25 wt%, indicating no impact on usage intensity. Moreover, mMCC/PBS composite monofilaments showed excellent tensile elasticity (up to 95%), excellent fatigue resistance, and low residual strains under small deformation (15%). Notably, the addition of 15–35 wt% mMCC increased the degradability of composite monofilaments, the degradation rate following 100 days of treatment in an aqueous environment ranged from 3.8%(PBS) to 4.7% (P-mM25), and the degradation rate following 180 days of burial in soil ranged from 3.9%(PBS) to 12.3% (P-mM35). Overall, our work significantly enhanced the compatibility between MCC and PBS without the use of any high-cost modifiers or complex processing methods, and successfully developed mMCC/PBS composite monofilaments that exhibit excellent dimensional stability during use and quick degradation after disposal.
... Figures 3 a and b show the wide-angle X-ray fiber diffraction patterns of the four different crystalline cotton cellulose. The XRD patterns of cellulose I β (Finkenstadt and Millane 1998), II (Langan et al. 1999), III I (Wada et al. 2004), and IV I (Gardiner and Sarko 1985) simulated based on cif files are also provided in Fig. 3 a and (105) crystal planes of cellulose I, respectively. Therefore, the crystal lattice of cellulose in cotton fibers has not been destroyed during the waste cotton recycling process. ...
Peroxymonosulfate (PMS) activated by nitrogen-doped carbon catalysts shows outstanding performance in wastewater treatment. Using cotton fibers with four crystalline structures from waste cotton as the carbon source and low-cost urea as the nitrogen source, four nitrogen-doped carbon catalysts (CU-I, CU-II, CU-III, and CU-IV) were prepared via carbonization and applied to activate PMS for degrading Reactive Blue 19 in wastewater. The results proved cotton fiber III as the preferred crystal structure. Within 40 min, the degradation efficiency of CU-III/PMS on Reactive Blue 19 reached 99%. Furthermore, CU-III exhibited an excellent degradation efficiency in a wide pH range from 3 to 11. After four degradation cycles, the degradation rate could still reach about 60%. The existence of ·OH, SO4cent years, advanced o, ¹O2, and O2·− reactive oxygen species (ROS) in the CU-III/PMS system was confirmed by radical quenching experiments and electron paramagnetic resonance spectroscopy, which proved ¹O2 as the main ROS. Non-radical electron transfer processes were also involved in the degradation. The active sites (pyridine nitrogen, pyrrolic nitrogen, and C=C species) of the nitrogen-doped carbon catalysts played vital roles in PMS activation. The toxicity experiments of high-concentration ions and degradation experiments of different dyes demonstrated the promise of the CU-III/PMS system in treating wastewater with various dye pollutants. In general, the prepared catalysts provide a new idea for both waste cotton recycling and wastewater treatment.
Graphical abstract
... The unit cell of cellulose is monoclinic (P21) with lattice parameters of a = 7.78 Å, b = 8.20 Å, c = 10.38 Å, α = β = 90°, γ = 96.5° [3,24]. Cellulose bundles perform a significant role in reinforcing the plant cell wall attributing to intermolecular hydrogen bonding network between adjacent chains [21]. ...
... It was reported that each cellulose bundle consists of 5 to 48 microfibril chains [23]. The unit cell of cellulose is monoclinic (P2 1 ) with lattice parameters of a = 7.78 3,24]. Cellulose bundles perform a significant role in reinforcing the plant cell wall attributing to intermolecular hydrogen bonding network between adjacent chains [21]. ...
The coconut shell consists of three distinct layers: the skin-like outermost exocarp, the thick fibrous mesocarp, and the hard and tough inner endocarp. In this work, we focused on the endocarp because it features a unique combination of superior properties, including low weight, high strength, high hardness, and high toughness. These properties are usually mutually exclusive in synthesized composites. The microstructures of the secondary cell wall of the endocarp at the nanoscale, in which cellulose microfibrils are surrounded by hemicellulose and lignin, were generated. All-atom molecular dynamics simulations with PCFF force field were conducted to investigate the deformation and failure mechanisms under uniaxial shear and tension. Steered molecular dynamics simulations were carried out to study the interaction between different types of polymer chains. The results demonstrated that cellulose–hemicellulose and cellulose–lignin exhibit the strongest and weakest interactions, respectively. This conclusion was further validated against the DFT calculations. Additionally, through shear simulations of sandwiched polymer models, it was found that cellulose–hemicellulose-cellulose exhibits the highest strength and toughness, while cellulose–lignin-cellulose shows the lowest strength and toughness among all tested cases. This conclusion was further confirmed by uniaxial tension simulations of sandwiched polymer models. It was revealed that hydrogen bonds formed between the polymer chains are responsible for the observed strengthening and toughening behaviors. Additionally, it was interesting to note that failure mode under tension varies with the density of amorphous polymers located between cellulose bundles. The failure mode of multilayer polymer models under tension was also investigated. The findings of this work could potentially provide guidelines for the design of coconut-inspired lightweight cellular materials.
... The wide angle X-ray fiber diffraction profiles of cotton fibers before and after TiO 2 loading are shown in Fig. 3. The simulated XRD patterns of cellulose I β (Finkenstadt and Millane 1998), II (Langan et al. 1999), III I (Wada et al. 2004a) and IV I (Gardiner and Sarko 1985) cif files and the standard XRD pattern of anatase TiO 2 (JCPDS No.21-1272) are also provided for comparison and analysis. As illustrated in Fig. 3a, the diffraction peaks at 2θ = 14.8°, 16.7°, 20.6°, 22.9°, 27.9°, 34.5°, 41.9° and 45.0° in the C-I and T-C-I fibers are well correlated with the (1-10), (110), (102), (200), (013), (004), (204) and (105) crystal planes of cellulose I β , respectively (French 2014). ...
The amount of photocatalysts loaded on the supporting materials and their bonding configuration by physical or chemical mode have great effects on the photocatalytic properties and stabilities of the photocatalytic composites in practical application. However, to our knowledge, the influence of the crystal structure of support material on the photocatalytic performance of the resultant photocatalysts has never been studied till now. Herein, four polymorphic cotton fibers (cellulose Iβ, II, IIII and IVI) were utilized as the support to load anatase TiO2 nanoparticles by a hydrothermal method. The structural changes of cotton fibers before and after loading TiO2 were characterized by scanning electron microscopy, transmission electron microscopy, X-ray diffraction, thermal gravimetric analysis, X-ray photoelectron, diffuse reflectance and photoluminescence spectroscopies. Their photocatalytic properties were examined towards the photodegradation of the model Congo red (CR) dye under visible light illumination. Results indicate that the crystalline structure of cotton cellulose affects the loading dosage of anatase TiO2 nanoparticles on cotton fibers and the doping ratio of C, N and O elements in TiO2, which results in the differences of the degradation rates of CR dye over the TiO2 modified cotton fibers. Because the TiO2 hydrothermal modification makes the crystallinity and orientation degree of cotton cellulose II decrease, the cotton cellulose II fibers might load more TiO2 nanoparticles than the other three cotton cellulose fibers via the bonds of C-Ti³⁺/Ti⁴⁺, N-Ti³⁺/Ti⁴⁺ and O-Ti³⁺/O-Ti⁴⁺. This leads to a narrowed band-gap of the resultant composites which exhibit a high photocatalytic activity for the photodegradation of CR dye. The density functional theory calculations demonstrate that the different crystalline structures of cotton cellulose I, II, and IVI affect the densities of state of C, N and O co-doped TiO2, thus resulting in various band-gaps.
Graphical abstract
... The insolubility of cellulose in most of the common inorganic and organic solvents are attributed to complex intermolecular and intramolecular hydrogen bonding network in the cellulose chains [6]. Although great efforts have been devoted in the development of efficient and benign solvents for cellulose dissolution, direct dissolution and derivatization of cellulose remains complex and challenging for the researchers [7][8][9]. ...
Cellulose is most abundant biopolymer on earth and can be utilized as sustainable resources for many applications, however, their utilization at great extent is limited due to lack of benign and recyclable solvent. While N-methylmorpholine-N-oxide (NMMO), used in Lyocell process, is thermally unstable and may undergoes runaway conditions, commercialization of ionic liquid as solvent still suffers from recyclability issues. Herein, we present the synthesis of a series of zwitterions, composed of tethered alkyl imidazolium cation and carboxylate anion, and investigate their cellulose dissolution characteristics. Effect of alkyl chain length of imidazolium ring on its dissolution efficiencies was studied and amongst synthesized zwitterions, the hexanoate derivatives exhibited 13% (w/w) cellulose dissolution at 100-125 °C. Thermal stability of zwitterions and their cellulose solution was characterized by DSC-TGA and found to be more stable than the NMMO and Lyocell solution. Rheological studies indicate that cellulose solution in zwitterions are viscoelastic and in spinnable range of fibre processing. Structural and morphological characterization of regenerated cellulose using elemental analysis, FTIR, DSC-TGA, GPC, XRD and SEM showed that zwitterions have no adverse effect on its physicochemical and morphological properties. A method for recovery and purification of solvent after cellulose dissolution and regenerations is also presented.
... The physical properties of the cellulose, among which are swelling, adsorption and accessibility for chemical modification Intra-and intermolecular hydrogen bonds within a cellulose structure [44] are influenced by these crystalline structures [47]. The first study work giving details of the crystalline structure, and the packing of native celluloses was reported by Meyer et al. [48] The report proposed that ramie cellulose has a structure with a monoclinic unit cell. The unit cell is made of two anti-parallel polysaccharide chains with dimensions a = 0.835 nm, b = 0.79 nm. ...
... The unit cell is made of two anti-parallel polysaccharide chains with dimensions a = 0.835 nm, b = 0.79 nm. Where c is the fiber axis, equal to 1.03 nm, and γ = 84° [48] A different model of the native crystalline structure of alga Valonia having a triclinic unit cell was reported by Finkenstadt and Millane [49]. ...
... This movement rapidly forms an intermediary complex by protonation of the glycosidic linkage, as shown in Figure 4 [40]. The protonation of the β-1,4-glucosidic bonds results in the slowly scissioning of the bond, thereby producing fragments of rod-like CWs [48]. The slitting of the hydrolytic cleavage of the glycosidic linkage bond is the ratedetermining step of the process. ...
This paper provides a review of cellulose, sources, extraction, molecular structure, cellulose whiskers, preparations, and morphology. The mechanical and thermal properties of cellulose reinforced composites are also discussed. Detail structure of Nano whiskers is also reported. As a renewable biomaterial, the most common source of cellulose is the plant. These plants include fruit fibers (coir), seed fibers (cotton), wood, leaf fibers (sisal), bast fibers (jute, kenaf, and hemp). Other sources of cellulose are from microorganisms such as fungi, tunicates, bacteria, and algae. Cellulose whiskers are isolated from cellulose fibers by acid hydrolysis. Cellulose micro fibril structures are made of both amorphous and crystalline regions. The amorphous regions are vulnerable to hydrolysis by acids compared to the crystalline domains. Several techniques among which are Field Emission Scanning Electron Microscopy (FESEM), Transmission electron microscopy (TEM) and Atomic Force Microscopy (AFM) have been used to study the morphology of cellulose whiskers. An interface between cellulose whisker and matrix is a transition zone between the matrix and the cellulose whiskers. It plays an important role in the overall mechanical properties of the composites. A soft interface domain will yield a greater resistance to fracture, while the composite will be low in stiffness and strength. On the other hand, a stiffer interface domain may cause the composite to be strong and stiff and less resistant to fracture. The addition of CW into polymers matrices has little or no effect on the glass transition temperature, (Tg) except on the modification of CW.
... In addition, an attempt is made in this work to compare the theoretically predicted bond length of individual elemental units calculated from the DFT analysis, with the short-range structural information evaluated by the PDF analysis. 32,33 These comparisons are done for both triclinic wollastonite phases of calcium silicate (W1, W2) and wollastonite-cellulosic nanocomposites (WC1, WC2). ...
The 100% phase pure calcium silicate nanoparticles (CSNPs) of the α‐wollastonite phase by hydrothermal synthesis is achieved first. Next this work reports the first‐ever microwave‐assisted low temperature synthesis of calcium silicate‐cellulose nanograss composites. The characterization by FESEM studies confirm that calcium silicate‐cellulose composites possess the nanograss like morphology spread over the matrix of calcium silicate. The structural information of the calcium silicate‐cellulose composites are derived by both theoretical and experimental techniques. Low‐energy ground state geometrical structures of the cellulose on the triclinic wollastonite surfaces and their interactions have been primarily determined by Density Functional Theory. Accordingly, the short‐range structural information is confirmed by Pair Distribution Function analysis. Structural information along with binding interactions are also confirmed from X‐ray photoelectron spectroscopy. The implications of these detailed analysis of structures in tuning the properties of such ceramic polymeric hybrid composites for futuristic endodontic application is discussed.
... 13 Molecular modeling has been used to ease the complication of the quantitative analysis of X-ray diffraction to determine the best and consistent coordinate set within the unit cells for both diffraction data and total potential energy. 14 The modelled microstructure of two native Iα and Iβ crystallographic phases and an amorphous solid has been illustrated in Figure 4. 12 The fibrils of crystalline cellulose are oriented at an angle of about ±10˚with±10˚with the fiber axis in the cell wall and provide high tensile strength to fiber. 7 However, structural information on amorphous cellulose is limited compared to crystal structures of cellulose and molecular modeling is a well adapted technique in such case to study the arrangement of the cellulose chains within the material. ...
Linum UsitatissimumL. is mostly known as flax usually cultivated to consume the fibre demand for apparel and edible oil production. However, recent development and research work have made the diversification of flax polymers to be a part of a growing trend to fabricate biodegradable composites. Although, flax is traditionally grown for its natural plant oil seeds, but it also carries the prospects to be applied in bio-composites either in form of reinforcements or as polymer matrix. Since flax is a biodegradable polymer, the use of flax in composite reinforcement can introduce the concept of green composite that may contribute in lowering the carbon footprint around the globe. The inherent composite characteristics of flax fiber provide outstanding mechanical properties. Further, the technology for producing bio-based resin from flax oil for industrial application has added additional value offering significant opportunities for new and improved materials from renewable resources. This review intends to discuss few of the key points that summarize the promising features of flax in fabricating biodegradable composites. VARTM is one of the significant manufacturing methods of flax reinforced composites using non-woven flax mat where flax mat is usually formed by web formation method through air or wet lying technique. Flax fibre properties, effect of manufacturing parameters like needle punch density, mat areal density and consolidation pressure while manufacturing composites play an important role on the strength and modulus of flax reinforced composites.......
[visit- https://doi.org/10.15406/jteft.2019.05.00212
or
https://medcraveonline.com/JTEFT/biopolymer-flax-linum-usitatissimum-l-and-its-prospects-in-biodegradable-composite-fabrication--a-short-review.html ]
... Cellulose is insoluble in most organic solvents and water. Therefore, there has been significant effort to find ways to process cellulose using new solvents and reagents 42 , dating back to the viscose method that uses carbon disulphide 43 After cellulose xylan is the second most abundant biopolymer, on earth 45 . Xylan is found in the cell walls of plants and comes in a wide range of structures, where this diversity in structures is correlated with their functions in the plants they are found. ...
Solutions of xylan and xylose in 1-ethyl-3-methylimidazolium acetate [C2mim] [OAc], a room temperature ionic liquid, were examined across a range of temperatures (20°C–70 °C) using: NMR spectroscopy; diffusion; low-field (20 MHz) spin–lattice and spin–spin relaxation times; and rheological measurements through the zero shear rate viscosity. The addition of xylose and xylan affect the mobility of the ions, with a decrease occurring when the carbohydrate concentration is increased. The ratio of the diffusion coefficients for the anion to the cation remained constant upon the addition of both xylan and xylose, showing that the anion and cation were equally affected by the presence of the carbohydrate. The translational diffusion motion of the ions in the xylose solutions were similar in value to published results for cellobiose, which we explain in terms of the number of available carbohydrate OH groups that the ions are interacting with. We observe from the various NMR results that the dissolving mechanism of xylan in [C2mim] [OAc] is similar to that for cellulose.
... It has been widely used for applications in fiber, paper, painting and pharmaceutical industries. Nevertheless, cellulose is poorly soluble in water due to strong hydrogen bonding between hydroxyl groups on the glucose from one chain with oxygen atoms on the same or on a neighbor chain [12]. Thus, soluble cellulose derivatives have been obtained by chemical modification and used as a hydrophilic building block to prepare amphiphilic copolymers, such as ethyl cellulose [13][14][15], hydroxyl propyl cellulose (HPC) [16], hydroxyl propyl methyl cellulose (HPMC) [16], hydroxyl ethyl cellulose [17], etc. ...
