Cellulose Crystallites Research Articles

The impact of the phase composition of bacterial cellulose on the low-temperature mobility of its molecules

We describe the properties of the bacterial cellulose of various origins obtained with the help of XRD, FTIR, and dielectric spectroscopy methods. The samples were produced by Gluconacetobacter bacteria (with Іα phase content of 36%) and a symbiotic culture of bacteria and yeasts present in Kombucha fermented drink (with Іα phase content of 62%). An increase in the Іα phase concentration results in a decrease in the intensity of the low-temperature dielectric relaxation and its shift toward higher temperatures. We demonstrate that this dielectric relaxation occurs primarily due to the reorientation of the methylol groups on the surfaces of the cellulose crystallites. We also report that the concentration of the activated relaxers in Іβ cellulose allomorph exceeds that of the Іα allomorph.

Cellulose nanocrystals engineered TPS/PBAT granulation through extrusion process and application for compostable carry bags

An economical and scalable process route has been developed for preparation of bio nanofillers, cellulose nanocrystals (CNCs) using acid hydrolysis and ceramic membrane-based continuous neutralization process alternative to conventional dialysis process. Optimized process achieved 42 % yield with crystallinity index of 91.3 % and average size 20–50 nm as confirmed by TEM analysis. Solid-state NMR result shows that the CNCs lateral dimension is comparable to elementary cellulose crystallites. Prior optimized composition of CNCs (Kesari et al., 2022) in TPS was used to prepare bio-nanocomposite with aim to reduced Poly (butylene adipate co-terephthalate) (PBAT) content in packaging films. A strong evolution in the mechanical and rheological properties of the CNCs reinforced blends was observed with increase in PBAT content with optimum blending ratio of 70/30. The composite attained tensile strength and young’s modulus of 11.01 ± 0.15 and 1200.94 ± 16 MPa, respectively with water vapor transmission rate (WVTR) of 63.96 ± 1.02 g/m2/day than neat PBAT (124.56 ± 6.89) which has higher vapor permeation. The thermal analysis confirms with bio nanofillers addition reduced the processing temperature of the polymeric blend. Thus, this work provides an economical and sustainable pathway for high content of biobased carbon (>70 %) for biodegradable packing industry.

Pretreatment greatly facilitates ethyl levulinate production from catalytic alcoholysis of Napier grass stem

The inhibition effect of impurities in the raw lignocellulosic biomass greatly impedes its direct acid-catalyzed alcoholysis process to produce downstream chemicals. Previous literatures widely investigated the inhibition problems of lignin content and cellulose crystallite in the raw biomass for the production of alkyl levulinate (AL), while the effect of inorganic matters on this process only received cursory attention. In this contribution, the vital importance of ash removal in raw material for efficient catalytic alcoholysis of cellulose fraction been highlighted. Moreover, it has been found that the facile pretreatment of Napier grass stem greatly facilitates the acid-catalyzed alcoholysis of its cellulose fraction towards ethyl levulinate (EL), a versatile commodity chemical. EL yield as high as 72.1 % can be accomplished from the NaOH-pretreated Napier grass stem in ethanol/γ-valerolactone co-solvent medium over Al(OTf)3 at 170 ℃ for 150 min, which is almost ten times that from the pristine one in ethanol medium. It is also interesting to note that a facile and green water prewashing treatment can efficiently remove the inorganic component of the raw biomass, which thus largely promotes the conversion of Napier grass stem to EL. The activation energies of cellulose degradation and glucopyranoside alcoholysis after pretreatment decreased to 62.4 kJ/mol and 68.6 kJ/mol, respectively. This work presents a highly-reliable strategy for valorizing grass lignocellulosic feedstock to produce bio-based ester compounds.

Dielectric relaxation and polaron hopping in biomass derived activated carbon

Activated carbon samples were obtained by alkali (KOH) activation and subsequent carbonisation of an identified biomass precursor at 600 °C, 800 °C, 1000 °C, and 1200 °C temperatures, in nitrogen atmosphere. Dielectric property changes with respect to the change in microstructure in the activated carbon samples was studied. High dielectric constant values at low-frequency regions (<103 Hz) were observed in all samples, due to trapped K+ ions, polar groups (C = C, C = O, –NH2, –OH), and interfacial polarisation. The trapped K+ ions also contributed to high dielectric dispersion at low-frequency regions. Carbonisation at 600 °C resulted in amorphous carbon formation with some intact cellulose crystallites. Thermal de-trapping of K+ ions resulted in an increase in dielectric constant with frequency up to 103 Hz. Carbonisation at 800 °C and 1000 °C resulted in nanocrystalline graphene oxide (GO), with interfacial polarisations dominant in charge storing and in the relaxation processes. Carbonisation at 1200 °C resulted in a carbon nanotube (CNT) network and negative dielectric constant values at 70 °C was observed due to the Surface Plasmon Resonance effects of the formed CNT. With increase in carbonisation temperature, a change in Debye-type to non-Debye-type relaxation process was observed, supported by the Dielectric formalism studies and the Cole–Cole plot.

Combined X-ray diffraction tomography imaging of tension and opposite wood tissues in young hybrid aspen saplings

Combining spatially localized X-ray diffraction (XRD) with X-ray microtomography (XMT) enables the mapping of the micro- and nanoscale structures simultaneously. The combination of these methods results in a powerful tool when considering the structural studies of hierarchical materials, allowing one to couple the relationships and connections of the structures at various scales. In this study, XMT was used to map the anatomy and cellular structures in 3D in tension and opposite wood with 1.5 µm resolution, while XRD was used to determine the cellulose crystallite widths and microfibril orientations with 100 µm spatial resolution within the same tissues. Tension wood (TW) has an important biological function with clearly distinct properties to opposite (OW) and normal wood, e.g. differing cellular structures with a higher cellulose content. This is the first study of very young hybrid aspen saplings (1-month-old) using the combined diffraction tomography method. The TW tissues could be identified from the OW tissues based on both the XMT and XRD results: TW had a higher average size of the cellulose crystallites and smaller mean microfibril angles (mMFA) than those in OW. With the XRD data, we were able to reconstruct the images of the cross sections of the saplings using the structural parameters (cellulose crystallite width and mMFA) as contrast mechanisms. As far as the authors know, there are no previous studies with images on any TW samples using the XRD-based contrast. Home laboratory bench-top set-up offers its advantages for these studies, considering the number of samples characterized, time-dependent studies and larger field of views.

Novel Natural Cellulosic Fiber from Lotus Stem: Structure and Performance Characterization

ABSTRACT The systematic exploration of the application prospects of lotus stem fibers (LSFs) in natural composites is significantly important for the development of green, lightweight, functional biomass materials and products. In this study, the physical and chemical properties, micro/nano structures, micromechanical characteristics, cellulose crystallinity, and thermal stability of LSFs were systematically explored. The density, microstructure, and nanoindentation analyses revealed that the LSF is a lightweight natural fiber with a high modulus (11.2–11.7 GPa) and a good hardness (0.41–0.57 GPa). The transmission electron microscopy analysis indicated the existence of four types of sclerenchyma cells in a gradient distribution in the epidermis and exodermis of the LS. The chemical analysis, X-ray diffraction, and Fourier transform infrared spectroscopy indicated that the outer-layer LSFs have a high cellulose content (44.73%), high relative crystallinity index (49.2%) of cellulose, and small cellulose crystallite size (2.2 nm). As a result, these LSFs possess good mechanical properties.

Molecular and crystal structures of cellulose in severely deteriorated archaeological wood

Preservation and conservation of archaeological wooden artifacts is extremely challenging due to a lack of knowledge about the hierarchical structure of preserved cellulose. Herein we report on the comparative analysis of eight archaeological and four recent wood samples from three archaeological sites in China by a variety of methods, including micro-morphology, Fourier Transform Infrared Spectrum, X-ray scattering, chromatographic analysis of wood sugars, and solid state 13C CP/MAS NMR. Results show that deterioration on the microscale is clearly related to a fragmentation of both the cellulose crystallite structure and the cellulose microfibrils. Slightly deteriorated archaeological wood features cellulose crystallites and microfibrils, comparable to non-degraded recent wood, whereas severely deteriorated wood shows higher porosity of the wood cell wall, fragmented cellulose aggregates instead of fibrils and nearly no crystallinity. Alterations in molecular structures resulted in advanced degradation of both amorphous and crystalline cellulose domains. Only a small amount of cellulose was preserved. The data allows to assume highly fragmented but still partially crystalline cellulose lamellas.Graphical abstract

Supramolecular Deconstruction of Bamboo Holocellulose via Hydrothermal Treatment for Highly Efficient Enzymatic Conversion at Low Enzyme Dosage.

Hydrothermal pretreatment (HTP) has long been considered as an efficient and green treatment process on lignocellulosic biomass for bioconversion. However, the variations of cellulose supramolecular structures during HTP as well as their effects on subsequent enzymatic conversion are less understood. In this work, bamboo holocellulose with well-connected cellulose and hemicelluloses polysaccharides were hydrothermally treated under various temperatures. Chemical, morphological, and crystal structural determinations were performed systematically by a series of advanced characterizations. Xylan was degraded to xylooligosaccharides in the hydrolyzates accompanied by the reduced degree of polymerization for cellulose. Cellulose crystallites were found to swell anisotropically, despite the limited decrystallization by HTP. Hydrogen bond linkages between cellulose molecular chains were weakened due to above chemical and crystal variations, which therefore swelled, loosened, and separated the condensed cellulose microfibrils. Samples after HTP present notably increased surface area, favoring the adsorption and subsequent hydrolysis by cellulase enzymes. A satisfying enzymatic conversion yield (>85%) at rather low cellulase enzyme dosage (10 FPU/g glucan) was obtained, which would indicate new understandings on the green and efficient bioconversion process on lignocellulosic biomass.

Modified acid pretreatment to alter physicochemical properties of biomass for full cellulose/hemicellulose utilization

Acid pretreatment of biomass decomposed hemicelluloses but could not effectively remove lignin, which hindered biomass saccharification and carbohydrates utilization. In this work, 2-naphthol-7-sulfonate (NS) and sodium bisulfite (SUL) were simultaneously added to acid pretreatment, which was found to synergistically increase hydrolysis yield of cellulose from 47.9 % to 90.6 %. Based on in-depth investigations, strong linear correlations were observed between cellulose accessibility and lignin removal, fiber swelling, CrI/cellulose ratio, cellulose crystallite size, respectively, indicating that some physicochemical characteristics of cellulose played significant roles in improving cellulose hydrolysis yield. After enzymatic hydrolysis, 84 % carbohydrates could be liberated and recovered as fermentable sugars for subsequent utilization. Mass balance illustrated that for 100 kg raw biomass, 15.1 kg xylonic acid and 20.5 kg ethanol could be co-produced, indicating the efficient utilization of biomass carbohydrates.

Self-assembling hierarchical flexible cellulose films assisted by electrostatic field for passive daytime radiative cooling

Natural cellulose materials possess hierarchical microstructures and high crystallinity, which gives the possibility to develop high-performance cellulose structural materials. However, the hierarchical microstructures of natural cellulose materials will be disappeared in regenerated cellulose materials owing to the dissolution process. Achieving hierarchical microstructures and high crystallinity as natural cellulose materials in flexible regenerated cellulose materials is an arduous challenge. Herein, a simple electrostatic-field-assisted self-assembly strategy is proposed to greatly boost the crystallization of regenerated cellulose materials and obtain hierarchical flexible fibrous cellulose film. Large areas of cellulose crystallites with the lattice spacing close to monoclinic cellulose II are presented, and crystallinity as high as 71.0 % is achieved for the self-assembled fibrous cellulose film. Moreover, the self-assembled cellulose film has a bioinspired fibrous morphology with anisotropic hierarchical microstructures, and therefore can be used as flexible passive daytime radiative cooling materials with subambient cooling up to 11.3 °C in hot summer. It is the first time to realize high crystallinity and hierarchical microstructures in regenerated cellulose materials by the self-assembly of cellulose macromolecules at the molecular level. This strategy provides new perspectives for the development of advanced flexible cellulose materials with hierarchical microstructures and high crystallization from natural cellulose resources.

Nanoscale Mechanism of Moisture-Induced Swelling in Wood Microfibril Bundles.

Understanding nanoscale moisture interactions is fundamental to most applications of wood, including cellulosic nanomaterials with tailored properties. By combining X-ray scattering experiments with molecular simulations and taking advantage of computed scattering, we studied the moisture-induced changes in cellulose microfibril bundles of softwood secondary cell walls. Our models reproduced the most important experimentally observed changes in diffraction peak locations and widths and gave new insights into their interpretation. We found that changes in the packing of microfibrils dominate at moisture contents above 10–15%, whereas deformations in cellulose crystallites take place closer to the dry state. Fibrillar aggregation is a significant source of drying-related changes in the interior of the microfibrils. Our results corroborate the fundamental role of nanoscale phenomena in the swelling behavior and properties of wood-based materials and promote their utilization in nanomaterials development. Simulation-assisted scattering analysis proved an efficient tool for advancing the nanoscale characterization of cellulosic materials.

Insights on the cellulose pretreatment at room temperature by choline-chloride-based deep eutectic solvents: an atomistic study

The pretreatment or disruption of a cellulose I \(\beta \) crystallite by four deep eutectic solvents (DES): choline-chloride ethylene glycol, choline-chloride oxalic acid, choline-chloride urea, and choline-chloride levulinic acid, was described from the atomistic interactions observed in molecular dynamics and ab-initio (NCI-AIM) studies. The cellulose I \(\beta \) disruption was studied considering plausible correlations between the Kamlet-Taft (α and β) solvent parameters, and a series of thermodynamic, structural, and energetic properties. It was found that the Kamlet-Taft parameters correlated with the thermodynamic properties of the DES, as well as their variations after the addition of the cellulose crystallite. Structural analysis revealed that the weaker the interactions within the molecules of the solvent, the stronger the interactions between the hydroxyl group from cellulose with the chloride anion and with the hydrogen bond donor. Further analysis indicated that the \(R-CO-R\) moieties in the hydrogen bond donor within the solvent, displayed best interplaying with the cellulose. The hydrogen bond occupancies within the cellulose crystallite, evidenced that the main \(O6-H6\cdots O2/O3\) and \(O2-H2\cdots O6\) interchain hydrogen bonds in the glucan located at the edge of the solute, were replaced by weak \(O6-H6\cdots O4\) hydrogen bonds in all solvents. This effect was related to the \({O/Cl}_{DES}\cdots H-donor\) and \({O}_{DES}-{H}_{DES}\cdots acceptor\) HBs between cellulose and DES molecules, and it was confirmed by the non-covalent interactions obtained through DFT calculations. The energetic interactions and the atomistic degree of disruption of the cellulose crystallite, were not completely described by the Kamlet-Taft β or α parameters when considered separately. Surprisingly, by using the net basicity (\(\beta -\alpha \)) definition such correlations were improved, suggesting that both parameters must be considered together to develop new, green, and sustainable solvents for cellulose pretreatment process.Graphic abstract

Fabrication of nanocellulose fibril-based composite film from bamboo parenchyma cell for antimicrobial food packaging

The development of nanocellulose fibril (NCF)-based films for use in food packaging has aroused tremendous attention because of their good biodegradability. In this work, NCFs isolated from bamboo parenchyma cell were used to fabricate the composite film with embedded silver nanoparticles (AgNPs). Results demonstrate that the low content of AgNPs, especially at content of 0.1 wt% in the composite film could slightly improve the tensile strength and Young's modulus of the composite film by about 11.0%, owing to the reduced thickness of cellulose crystallites and decreased amount of adsorbed water, as well as the increment in crystallinity and the hydrogen-bond intensity confirmed by X-ray diffraction measurement and Fourier transform infrared spectra. On the other hand, high content of AgNPs could enhance antimicrobial activity and thermal stability while showed negligible negative effect on tensile properties. Specifically, the maximum inhibition zone of the composite film (with AgNPs content of 0.1 wt%) was 13.5 ± 0.8 mm against Salmonella typhi (S. typhi) and 7.5 ± 0.3 mm against Escherichia coli (E. coli). The strong antimicrobial activity of NCF-based films highlights their potential as a biodegradable food packaging material.

Wide-angle X-ray scattering studies on contemporary and ancient bast fibres used in textiles \u2013 ultrastructural studies on stinging nettle

Stinging nettle (Urtica dioica) is a potential source material for industrial applications. However, systematic research on the ultrastructural properties of nettle fibres is lacking. Determining the ultrastructure of nettle and the other bast fibres also provides new insights into the studies of archaeological fibres and their usage. In this study, the nanostructure of modern and ancient nettle samples was studied using wide-angle X-ray scattering (WAXS) and compared to other bast fibres. The culturo-historical fibre samples consisted of nettle, flax, and hemp from White Karelian textiles collected 1894 as well as of 800–900-year-old archaeological textile fragments from Ravattula Ristimäki burial site, Finland. Using WAXS, the average cellulose crystallite widths, relative crystallinities and orientational order (including microfibril angle for the modern fibres) were determined and compared. The results also revealed the suitability of the WAXS analysis for fibre identification. The crystallite widths were of the similar size for all modern fibres (3.4–4.8 nm). Subtle differences in the relative crystallinities in descending order (from flax to nettle, and finally hemp) were observed. Also, subtle differences in the mean MFAs were observed (10 ± 1° for flax, 12 ± 1° for nettle, and 14 ± 1° for hemp). For the culturo-historical fibres, the values for crystallite widths and relative crystallinities were larger compared to the corresponding modern references. In addition, features due to the presence of non-cellulosic, crystalline substances (e.g., calcium oxalates) were detected in the WAXS patterns of all the modern nettle fibres. These features could potentially be used as a tool for identification purposes.Graphical abstract

Analyzing the effects of thermal stress on insulator papers by solid-state 13C NMR spectroscopy

Million tons of cellulosic paper have been used for insulating coils in oil-filled electrical power transformers, thereby assuring the electricity supply for our societies. The high working temperatures in transformers constantly degrade paper insulators throughout their service life of up to 40 years. We approached the structural changes in oil-immersed cellulosic paper samples upon thermal stress in a study that compared unbleached softwood Kraft paper used as insulator paper with pure cotton cellulose paper. The model experiments used a thermal treatment in transformer oil at 170 °C for up to 14 days. The samples were characterized by means of 13C CP/MAS NMR spectroscopy, mainly based on deconvolution of the C4 resonance. An automated, fast, and reproducible C4 resonance deconvolution employing the “Peak Analyzer” tool of OriginPro 2020 (OriginLab Corporation, USA) was developed and used to exploit 13C CP/MAS NMR spectroscopy for the characterization of thermally stressed paper samples. Our results show that thermally induced structural changes depend heavily on the composition of paper, that hornification and coalescence of fibrils take place, and that the allomorph composition of cellulose crystallites is altered under the given conditions.Graphical abstract

Timber Properties and Cellulose Crystallites Size in Pine Wood Cut in Different Sawing Patterns after Pretreatment with CH3COOH and H2O2 and Densification

One process to improve wood quality is densification or wood surface compression. Our study analyzed the changes in some basic properties of pine wood, including its anatomical structure, density, modulus of elasticity (MOE), and dimensions of cellulose crystallites, after densification following soaking pretreatment in CH3COOH and H2O2 at a concentration of 20%. Samples were sawn in radial and tangential directions for analysis of the wood. The results showed a change in the shape of tracheid cells from hexagonal to oval, as well as damage to the ray cell constituents on the tangential surface. The thickness decrease of the samples was in accordance with the target, which meant that spring-back was short. In general, the tangential boards had a higher density than the radial boards, with a lower MOE and crystallite dimensions. Our findings showed that the densified tangential board was stronger than the radial board.

All-natural and biocompatible cellulose nanocrystals films with tunable supramolecular structure

Herein, nanocomposites films were prepared via the facile casting method by incorporating cellulose nanocrystals (CNCs) with arabinogalactan (AG), galactomannan (GM) or konjac glucomannan (KGM) respectively. The introduced polysaccharides maintained the transparency of CNCs films and promoted the UV blocking properties. In addition, mechanical strength of the nanocomposite films was greatly improved after the combination of polysaccharides. The interactions of hydroxyl-abundant macromolecules, smoother and tighter morphological structures, as well as the disturbed crystal structure were proved to be responsible for the improved properties. Hydrophilic lattice planes of cellulose crystallites were determined to interact with polysaccharides resulting in lower crystallite sizes and crystallinity. The cell culture assay revealed that the films had no cytotoxicity and presented a satisfactory cytocompatibility, because of the polysaccharides from plant cell walls introduced into the films. Therefore, the biocompatible nanocomposites films can be tuned by the addition of polysaccharides, which show great potentials for materials modification in optical, packaging and biomedical fields.

MECHANISM OF DISORDER GENESIS IN CELLULOSE MICROFIBRILS

"We discuss the possible mechanism of genesis of disordered regions in cellulose microfibrils. In our work, we show that obstacles stopping the growth of nanofibrils and the further deformation of nanofibrils may be the reasons for disorder. In this case, the initial prismatic shape of nanofibrils becomes corrugated and regions, where cellulose chains lose their initial straight configuration, appear in it. If a pack of thus deformed nanofibrils form a microfibril, then it contains disordered regions of two types. The first one consists in boundary layers, which separate nanofibrils from each other. The second type represents amorphous regions located inside each nanofibril. In this discussion, we use the linear theory of elasticity. With its help, we estimated longitudinal dimensions of cellulose crystallites and then compared them with values of such sizes calculated based on experimental data. The experimentally obtained values turned out to be, to a certain extent, greater than the theoretically estimated ones."

Nanocomposites based on the cellulose extracted from the Amazon Peperomia pellucida and polyaniline derivatives: structural and thermal properties

POMA/Cellulose and POEA/Cellulose nanocomposites were successfully synthesized based on interfacial polymerization over cellulose fibers extracted from the Amazon P. pellucida. The triclinic structure of poly(o-methoxyaniline) (POMA) and poly(o-ethoxyaniline) (POEA) was maintained after polymerization over cellulose fibers. However, possible chemical interactions between polymers and cellulose chains resulted in the increase of the average crystallite size, suggesting an oriented polymerization as well as the cellulose surface modification. The average crystallite size of POMA changed from (32 ± 2) A (for pure POMA) to (41 ± 2) A (for POMA in the nanocomposite form). The average crystallite size of POEA changed from (32 ± 2) A (for pure POEA) to (44 ± 2) A (for POEA in the nanocomposite form). Initially, the extracted cellulose presented average crystallite size of (29 ± 2) A, while the cellulose crystallites in the nanocomposites were found around (59 ± 2) A (POMA/Cellulose) and (92 ± 2) A (POEA/Cellulose). The morphology of POMA/Cellulose was significantly different from that observed in the pure as-synthesized POMA: globular vesicular shape was formed during the polymerization over the cellulose surface. In the POEA/Cellulose nanocomposite, the cellulose nanofibrils were also completely recovered by POEA consisting of well-defined nanometric spheres. These results were correlated with the thermal stability of the developed nanocomposites by Thermogravimetric Analysis (TG/dTG). Thus, the interfacial synthesis of POMA and POEA over a cellulose matrix was reported here, contributing to a better understanding of the thermal, structural and morphological properties of these resulting nanocomposites.

Preferred crystallographic orientation of cellulose in plant primary cell walls

Cellulose, the most abundant biopolymer on earth, is a versatile, energy rich material found in the cell walls of plants, bacteria, algae, and tunicates. It is well established that cellulose is crystalline, although the orientational order of cellulose crystallites normal to the plane of the cell wall has not been characterized. A preferred orientational alignment of cellulose crystals could be an important determinant of the mechanical properties of the cell wall and of cellulose-cellulose and cellulose-matrix interactions. Here, the crystalline structures of cellulose in primary cell walls of onion (Allium cepa), the model eudicot Arabidopsis (Arabidopsis thaliana), and moss (Physcomitrella patens) were examined through grazing incidence wide angle X-ray scattering (GIWAXS). We find that GIWAXS can decouple diffraction from cellulose and epicuticular wax crystals in cell walls. Pole figures constructed from a combination of GIWAXS and X-ray rocking scans reveal that cellulose crystals have a preferred crystallographic orientation with the (200) and (110)/(1bar 10) planes preferentially stacked parallel to the cell wall. This orientational ordering of cellulose crystals, termed texturing in materials science, represents a previously unreported measure of cellulose organization and contradicts the predominant hypothesis of twisting of microfibrils in plant primary cell walls.