Cellulose最新文献

The cellulose catalytic oxidation system mainly comprises inorganic ion-based oxidants. Hence, the selective oxidation of C_6-primary hydroxy groups (C₆-OH) of cellulose, catalyzed by piperidine free radicals, was limited to the homogeneous cellulosic system containing protic solvents or heterogeneous system. In this work, the use of the catalytic system containing 4-acetamido-2,2,6,6-tetramethylpiperidine 1-oxyl (4-AcNH-TEMPO) was extended to the cellulosic solution in N, N-dimethylacetamide (DMAc) and combined with chlorine dioxide. Results showed that the carboxyl content was 0.832 mmol/g. Meanwhile, the degree of polymerization decreased from 900 to 489. This study provides an effective route for the homogeneous selective oxidation of primary hydroxy groups in cellulose and explored its oxidation mechanism in DMAc solvent. Furthermore, studies showed that the reactive chlorine species- ClO·, Cl·, and ClO₂ played a crucial role in the oxidation process. The methodology developed here displayed great potential to be utilized to various biomolecules in aprotic solvents homogeneous system based on 4-AcNH-TEMPO as oxidation catalysts.

Bio-based membranes are becoming highly-desired low-cost, environmentally friendly, and readily available supports for the separation and purification of biomacromolecules. In this work, weak cation-exchange and highly (> 95%) microporous (> 80 μm) cellulose-based membranes were prepared from different weight ratios of carboxymethyl cellulose (CMC) as anionic polymer and cellulose nanofibrils (CNFs) as a stabilizing and structural filler, by the freeze-casting process and citric-acid (CA) mediated in situ cross-linking (esterification). It was ascertained that mono-esterified/grafted CA also contributes to the total carboxylic groups (1.7–2.6 mmol/g), while the CMC-induced CNF orientation affected the membrane’s morphology and lysozyme (Lys) binding capacity. A static binding capacity (SBC) between 370 and 1080 mg/g, and equilibrium within 3.3 h for 1 g/mL Lys was thus achieved with increasing the total solid and CMC content by forming more isotropic microporous structures. The selected membranes were then packed in a chromatographic housing, analyzed for pressure drop, and evaluated for dynamic binding capacity (DBC), depending on the process performance (flow rates, Lys concentration). A DBC in the 165–417 mg/g range was determined at a throughput of 0.5 mL/min, and elution yield of 78–99% with > 95% recovery. The Lys adsorption and transfer were reduced by the increasing flow rate and membrane density due to compressibility issues, resulting in smaller and irregularly distributed pores and the unavailability of carboxylic groups. Although the DBC was still comparable with the commercial CIM® monoliths, the convection-based transport of molecules inside the membrane and the membrane stiffness needs to be improved in further research.

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Understanding the chemical characteristics and residual impurities of a dissolving pulp feedstock is necessary to enhance both the quality and processability of yielded cellulose acetates. Fiber fractionation was performed with three different cotton linter feedstocks. Biomass compositional analysis and fiber quality analysis were used to determine the carbohydrate content of the fractionated fibers and the quantity of fines. To evaluate the impact of fines on the acetylation of cotton linters, artificial fines were prepared from fractionated long fibers and added back to long fibers in varying fines content blends. The cotton linter pulps and artificial fines blends were used to generate acetates which were characterized via degree of substitution measurement by FTIR, the ensuing weight fraction of acetone insoluble substance, and the filtration rate of the acetate. A test to measure the amount of sulfuric acid insoluble substances (SIS) was developed to explain the formation of insoluble gel particles in acetate media; an R² of 0.97 was found between fines and resulting SIS. Then, SIS contents were correlated with the acetone insoluble substances in the acetates (R² = 0.98). Fines contents were found to be highly influential on the acetate’s degree of substitution, insoluble substance content, and filtration rate (R² = 0.99). Thorough activation and excess acetic anhydride reagent were found to limit the effects of fines on degree of substitution.

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Cellulose-based hydrogels have garnered significant interest in antimicrobial applications due to their exceptional biocompatibility, biodegradability, and superior mechanical properties. This in-depth investigation explores the various mechanisms and innovative strategies employed by cellulose-based hydrogels to exhibit remarkable antimicrobial activity. Our review aims to provide significant insights into utilizing the full potential of cellulose sources, cross-linking moieties, and polymerization processes on the structure, porosity, and mechanical properties of hydrogels by highlighting the major features and recent advancements in this developing sector. Additionally, we examine alternative functionalization methods for enhancing antimicrobial efficacy, such as incorporating antimicrobial moieties and surface modification. Understanding the mechanisms of action that disrupt microbial cell membranes and cell walls is crucial for comprehending their antimicrobial efficacy. Moreover, we assess the antimicrobial action of these hydrogels against various pathogens, including fungi and bacteria. Finally, we address recent achievements and future goals in this field, emphasizing the importance of continued research and collaboration. This demonstrates the potential of cellulose-based hydrogels as potent weapons in the battle against antimicrobial resistance.

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A novel preparation process is developed to effectively disperse biomass nanofibers such as cellulose, chitin, and chitosan nanofibers, in a hydrophobic bisphenol-A-type epoxy resin. The nanofibers (NFs) are incorporated into an amphiphilic epoxy resin and then mixed with the diglycidyl ether of bisphenol A. The mechanical properties of the epoxy resin improved by 27–39%. Differences in reinforcement properties based on the NF type are discussed in terms of aspect ratio, dispersibility, and interfacial adhesion with the epoxy matrix. Chitin nanofibers (ChNFs), which have the highest aspect ratio and relatively high hydrophobicity, show the strongest reinforcement because of their dense NF network and superior interfacial adhesion to the epoxy matrix. NF dispersion improved both tensile strength and elongation at break, making the NF/epoxy composites tougher than the neat epoxy resin, while increasing the impact and adhesive strength. The NF network structure has a low coefficient of thermal expansion (CTE) that restricts the molecular motion of epoxy chains, leading to lower CTE and higher glass transition temperatures than that of the neat epoxy resin. A wet-rotating disc milling (WRDM) process further improved NF dispersibility in the matrix, increasing the tensile strength and elongation at break of the WRDM-treated ChNF/epoxy composite by 48 and 71%, respectively, compared to that of the neat resin. This method successfully dispersed biomass NFs in a hydrophobic bisphenol A-type epoxy resin, enhancing its mechanical and thermal properties while addressing drawbacks of the epoxy resin such as brittleness, thermal expansion, and cure shrinkage.

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Aiming towards fully valorizing biomass, this study proposed an integrated process for eucalyptus to produce dissolving pulp, furfural and reactive lignin by using spiral extrusion with sequential p-toluenesulfonic acid (p-TsOH) pretreatment. Under optimal conditions (70 wt% p-TsOH, 80 °C, 50 min), 80.0% and 79.5% of lignin and hemicellulose were removed, respectively, while 92.2% of cellulose was retained in solid residue. After further cooking and bleaching processes, the dissolving pulp with 96.1% of α-cellulose content was obtained. Moreover, 75.6% of furfural yield was reached from the hydrolysate without additional catalysts for 170 °C at 50 min. The dissolved lignin showed low β-O-4 content and molecular weight with high phenolic OH content, which was suitable for lignin-based materials. This study provides a sequential valorization strategy for eucalyptus to produce dissolving pulp, furfural and reactive lignin, which would achieve the separation and directed transformation of all components of eucalyptus wood.

This study investigates the effect of green polar aprotic co-solvents such as N,N-Dimethylpropyleneurea (DMPU), dimethyl isosorbide (DMI), sulfolane (SLF), and γ-valerolactone (GVL) on the properties of regenerated cellulose. Binary solvent systems, containing superbase ionic liquid (SB-IL, 5-methyl-1,5,7-triaza-bicyclo-[4.3.0]-non-6-enium acetate) and green co-solvents, effectively dissolved cellulose without causing significant changes in cellulose molar mass. NMR and XRD analysis differentiated between cellulose allomorphs and demonstrated the impact of various co-solvents on the crystallinity of regenerated cellulose. Peaks characteristic of cellulose II allomorph appeared in regenerated samples, indicating disruption of the native cellulose I structure. The crystallite size and proportion of crystallite interior chains decreased in regenerated cellulose compared to native cellulose, indicating the reduced crystallinity and increased exposure of cellulose chains to various modifications. The TGA analysis revealed that the regenerated celluloses displayed two-step thermal degradation, related to the sequential degradation of amorphous and crystalline phases. The thermal stability, crystallinity index, and crystallite size hierarchy were determined as Cell-DMPU > Cell-SLF > Cell-DMI > Cell-GVL > Cell-DMSO, underscoring the influence of co-solvent type on the thermal and structural properties of regenerated cellulose.

The development of cotton fabrics with exceptional and durable fluorescent properties has garnered significant attention. In this study, an enduring fluorescence cotton fabric was fabricated by a convenient and efficient approach. Interestingly, carboxyl reactive groups were employed as bridging agents to covalently link the raw fabric with Europium (Eu)-based polyoxometalate, thus guaranteeing the tight bonds between the polyoxometalates and the fabric matrix. The morphology and microstructures of composite fabrics were characterized and compared, demonstrating the successful integration of polyoxometalates into the fabric featuring covalent bonding interactions. Additionally, the fluorescence emissions of composite fabrics were investigated (λ_ex = 243 nm). The emission spectrum exhibits typical emission peaks of Eu³⁺ and polyoxometalate, corresponding to the ⁵D₀ → ⁷F_0–4 transitions in the range of 550–750 nm and the O → W transition, which results in distinct red fluorescence. Moreover, the lifetime-decay behavior, monitored at an excitation wavelength of 243 nm, follows a single-exponential function, yielding a lifetime (τ) of 0.4 ms. More importantly, owing to the robust interaction between the components, the composite fabric demonstrates exceptional fastness properties, including resistance to washing (50 times washing), abrasion (under both dry and wet conditions), and sunlight (9 days). In particular, three kinds of shaped masks were used, highlighting its potential as a reusable anti-counterfeiting material. The plausible mechanisms of the system is attributed to the efficient electron transition and energy transfer processes within the composite structure. Besides, mechanical property reveal PW₁₁Eu@CF almost inherits the original fabric’s mechanical property. This work provides a novel strategy for the controlled design and fabrication of polyoxometalate-based anti-counterfeit material.

Superabsorbent polymers (SAPs) are three-dimensional crosslinked hydrophilic polymers, that can absorb and retain liquids up to hundreds of times their weight. These polymers have diverse applications across various fields, including agriculture, biomedicine, separation technologies, and wastewater treatment. Among these cellulose-based SAPs are prominent due to their biodegradable nature, sustainability, biocompatibility, cost-effectiveness, and natural abundance. The development of SAPs has evolved significantly since 1961, marked by advancements in polymerization techniques and their integration into numerous aspects of daily life. This review provides a comprehensive analysis of recent advancements in the field of cellulose-based superabsorbents, focusing on their polymerization methods, source of cellulose, and diverse applications. Furthermore, it highlights the mechanisms by which different forms of cellulose can enhance liquid absorption capacity and kinetics across various applications. The findings underscore the importance of cellulose-derived SAPs in promoting environmentally sustainable practices while addressing the growing demand for effective water retention solutions in agricultural and industrial contexts.

Due to their excellent wetting and liquid-spreading properties, cellulose-based aerogels have shown great potential as absorbent materials in many applications. However, there is still a very limited understanding of how the aerogels should be tailored to optimize liquid spreading and liquid storage properties. The present work focuses on characterizing liquid spreading at short contact times and tailoring the surfaces within the aerogel to increase the spreading properties. Aerogels from periodate oxidized cellulose nano fibrils (CNFs) were freeze-linked to attain wet stability. Subsequently, they were modified with the layer-by-layer (LbL) assembly method using poly(diallyldimethylammonium chloride) (PDADMAC) and well-defined SiO₂ nanoparticles to change their surface properties. The morphology of the untreated and treated aerogels, as determined from SEM images, indicates a complete surface coverage of PDADMAC/SiO₂ bilayers on the inner surfaces of CNF aerogels, showing that the LbL-treatment can be used to tailor the aerogel, i.e. to increase the specific surface area of the aerogel, by changing the number of bilayers. It has also been shown that the horizontal liquid spreading rate increases significantly after surface modification. In addition, a theoretical analysis of the spreading results indicates that this is due to the increase in the specific surface area of the surface-modified aerogels. Moreover, the spreading rate can be gradually tailored by changing the number of bilayers and the dimensions of the nanoparticles. Furthermore, we provide a new method to calculate the specific surface area of aerogel materials by combining the experimentally determined liquid spreading rate and a version of the well-known Kozeny–Carman equation.