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1.
Bioresour Technol ; 329: 124911, 2021 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-33667991

RESUMO

To enhance the cellulose hydrolysis at high solid loadings, an increased mixing intensity is generally required for the high solid loading hydrolysis, while it leads to higher energy consumption. In this study, the impact of mixing intensity on cellulose conversion during hydrolysis at different solid loadings were systematically studied. It was found that the increased mixing intensity is not necessary for more efficient cellulose hydrolysis. For cellulose hydrolysis at higher solid loadings, a lower mixing intensity is needed for a higher cellulose conversion. Although the increased mixing intensity promoted enzyme adsorption, it strengthened product inhibition and caused severer enzyme deactivation. Besides, mixing at the initial stage of cellulose hydrolysis was more crucial, while continuous mixing throughout the hydrolysis was not required for more efficient cellulose hydrolysis. Based on the mechanism study, a combined mixing strategy was developed to achieve efficient cellulose hydrolysis with about two-third reduction in energy consumption.


Assuntos
Celulase , Celulose , Adsorção , Hidrólise
2.
J Environ Manage ; 286: 112167, 2021 May 15.
Artigo em Inglês | MEDLINE | ID: mdl-33676135

RESUMO

In this study, the cellulose sulfate/chitosan aerogel (CCA) was prepared by chitosan and sulfonated cotton, and its efficiency was assessed for lead removal from contaminated waters. The adsorbent was determined by FESEM, EDS, FTIR, and BET analysis. The batch experiments were designed by Design-Expert software. At an initial lead concentration of 300 mg L-1, the contact time of 40 min, and the temperature of 26 °C, the maximum adsorption capacity and the removal efficiency were 137.8 mg g-1 and 91.9%, respectively. Also, the effect of ions including cations and anions at 100 mg L-1 was investigated, and it was found that the presence of anions does not have much effect on adsorption, but among cations, calcium and magnesium have the inhibitor effect on adsorption due to their double plosive. Adsorption isotherms were studied at different temperatures, and the kinetics of the reaction were investigated at different concentrations. Thermodynamic parameters indicated that the adsorption process was spontaneous, endothermic, and increasing irregularity at the adsorbent level. Adsorption recovery was performed five times adsorption and de-adsorption by hydrochloric acid 1 M washing and only 10% of adsorption capacity was decreased.


Assuntos
Quitosana , Poluentes Químicos da Água , Purificação da Água , Adsorção , Celulose/análogos & derivados , Concentração de Íons de Hidrogênio , Cinética , Chumbo , Temperatura , Termodinâmica
3.
Bioresour Technol ; 330: 124969, 2021 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-33740586

RESUMO

A promising approach to help offset production costs for the cellulosic ethanol industry is to improve ethanol productivity while simultaneously generating value-added by-products. This study reports integration of an advanced fermentation approach (self-cycling fermentation) with the production of cellulose nanocrystals. Specifically, wood pulp was enzymatically hydrolyzed to yield dissolved sugars, which were fed to a self-cycling fermentation system for ethanol production, and residual solids were used for cellulose nanocrystals production via acid hydrolysis. Self-cycling fermentation achieved stable ethanol production for 10 cycles with significantly greater productivity than batch operation: ethanol volumetric productivity increased by 63-95% and annual ethanol productivity by 96 ± 5%. Additionally, the enzyme hydrolysis approach employed did not impede ethanol fermentation, and the cellulose nanocrystals generated displayed properties consistent with previous studies. Taken together, these results highlight the potential of this co-production strategy to produce both cellulosic ethanol and cellulose nanocrystals from a single feedstock.


Assuntos
Celulose , Nanopartículas , Celulose/metabolismo , Etanol , Fermentação , Hidrólise , Madeira/metabolismo
4.
Bioresour Technol ; 330: 124984, 2021 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-33743277

RESUMO

Ionic liquids have been proven efficient and environmental medium for producing platform chemical levulinic acid. Lack of high-efficiency, stable and low-cost recovery strategy with complex electrolyte form restricts the further scale-up of ionic liquids for platform chemicals production. Membrane-based techniques including ultrafiltration (UF) and bipolar membrane electrodialysis (BMED) were employed for the high-efficiency recovery, regeneration and recycling of 1-ethyl-3-methylimidazolium hydrogen sulfate [Emim][HSO4] for levulinic acid production from sugarcane bagasse. UF-BMED treatment works based on the interception of macromolecule biomass degradation products by UF treatment with regional recovery of Emim+ and SO42- by BMED treatment. Effect of major parameters on [Emim][HSO4] recovery performance was determined. Recovery ratio for Emim+ and SO42- approached 95.4% and 95.9%. Energy consumption of specific [Emim][HSO4] recovery was closed to 5.8 kWh/kg. Insight gained from this study suggests a high-efficiency and economical strategy for platform chemicals production with green solvent ionic liquids.


Assuntos
Líquidos Iônicos , Saccharum , Celulose , Hidrogênio , Imidazóis , Ácidos Levulínicos , Sulfatos
5.
mBio ; 12(2)2021 03 02.
Artigo em Inglês | MEDLINE | ID: mdl-33653891

RESUMO

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), a causative agent of the CoV disease 2019 (COVID-19) pandemic, enters host cells via the interaction of its receptor-binding domain (RBD) of the spike protein with host angiotensin-converting enzyme 2 (ACE2). Therefore, the RBD is a promising vaccine target to induce protective immunity against SARS-CoV-2 infection. In this study, we report the development of an RBD protein-based vaccine candidate against SARS-CoV-2 using self-assembling Helicobacter pylori-bullfrog ferritin nanoparticles as an antigen delivery system. RBD-ferritin protein purified from mammalian cells efficiently assembled into 24-mer nanoparticles. Sixteen- to 20-month-old ferrets were vaccinated with RBD-ferritin nanoparticles (RBD nanoparticles) by intramuscular or intranasal inoculation. All vaccinated ferrets with RBD nanoparticles produced potent neutralizing antibodies against SARS-CoV-2. Strikingly, vaccinated ferrets demonstrated efficient protection from SARS-CoV-2 challenge, showing no fever, body weight loss, or clinical symptoms. Furthermore, vaccinated ferrets showed rapid clearance of infectious virus in nasal washes and lungs as well as of viral RNA in respiratory organs. This study demonstrates that spike RBD-nanoparticles are an effective protein vaccine candidate against SARS-CoV-2.


Assuntos
/prevenção & controle , Nanopartículas/química , Glicoproteína da Espícula de Coronavírus/metabolismo , Vacinas Virais/uso terapêutico , /química , Animais , Celulose/química , Coronavirus/imunologia , Coronavirus/patogenicidade , Furões , Ferritinas , Vacinas Virais/química
6.
Sensors (Basel) ; 21(4)2021 Feb 11.
Artigo em Inglês | MEDLINE | ID: mdl-33670269

RESUMO

Green sensors are required for the realization of a sustainable economy. Biopolymer-derived composites are a meaningful solution to such a needing. Bacterial Cellulose (BC) is a green biopolymer, with significant mechanical and electrical properties. BC-based composites have been proposed to realize generating mechanoelectrical transductors. The transductors consist of a sheet of BC, impregnated of Ionic Liquids (ILs), and covered with two layers of Conducting Polymer (CP) as the electrodes. Charges accumulate at the electrodes when the transductor is bent. Generating sensors can produce either Open Circuit (OC) voltage or Short Circuit (SC) current. In the paper, the OC voltage and SC current, generated from BC-based composites, in a cantilever configuration and subjected to dynamic deformation are compared. The influence of ILs in the transduction performance, both in the case of OC voltage and SC current is investigated. Experimental investigations of structural, chemical, and mechanoelectrical transduction properties, when the composite is dynamically bent, are performed. The mechanoelectrical investigation has been carried on both in the time and in the frequency domains. Reported results show that no relevant changes can be obtained because of the use of IL when the OC voltage is considered. On the contrary, dramatic changes are observed for the case of SC current, whose value increases by about two orders of magnitude.


Assuntos
Bactérias/química , Celulose/química , Líquidos Iônicos/química , Transdutores , Eletrodos , Polímeros
7.
Nat Commun ; 12(1): 1606, 2021 03 11.
Artigo em Inglês | MEDLINE | ID: mdl-33707445

RESUMO

Tuberculosis is a chronic disease that displays several features commonly associated with biofilm-associated infections: immune system evasion, antibiotic treatment failures, and recurrence of infection. However, although Mycobacterium tuberculosis (Mtb) can form cellulose-containing biofilms in vitro, it remains unclear whether biofilms are formed during infection in vivo. Here, we demonstrate the formation of Mtb biofilms in animal models of infection and in patients, and that biofilm formation can contribute to drug tolerance. First, we show that cellulose is also a structural component of the extracellular matrix of in vitro biofilms of fast and slow-growing nontuberculous mycobacteria. Then, we use cellulose as a biomarker to detect Mtb biofilms in the lungs of experimentally infected mice and non-human primates, as well as in lung tissue sections obtained from patients with tuberculosis. Mtb strains defective in biofilm formation are attenuated for survival in mice, suggesting that biofilms protect bacilli from the host immune system. Furthermore, the administration of nebulized cellulase enhances the antimycobacterial activity of isoniazid and rifampicin in infected mice, supporting a role for biofilms in phenotypic drug tolerance. Our findings thus indicate that Mtb biofilms are relevant to human tuberculosis.


Assuntos
Biofilmes/crescimento & desenvolvimento , Celulose/metabolismo , Farmacorresistência Bacteriana Múltipla/fisiologia , Mycobacterium tuberculosis/crescimento & desenvolvimento , Mycobacterium tuberculosis/metabolismo , Animais , Celulase/farmacologia , Modelos Animais de Doenças , Sinergismo Farmacológico , Humanos , Isoniazida/farmacologia , Camundongos , Camundongos Endogâmicos C57BL , Mycobacterium abscessus/crescimento & desenvolvimento , Mycobacterium avium/crescimento & desenvolvimento , Mycobacterium fortuitum/crescimento & desenvolvimento , Mycobacterium tuberculosis/efeitos dos fármacos , Rifampina/farmacologia , Tuberculose Pulmonar/tratamento farmacológico , Tuberculose Pulmonar/patologia
8.
Small ; 17(12): e2100139, 2021 03.
Artigo em Inglês | MEDLINE | ID: mdl-33656273

RESUMO

The novel coronavirus SARS-CoV-2 has prompted a worldwide pandemic and poses a great threat to public safety and global economies. Most present personal protective equipment (PPE) used to intercept pathogenic microorganisms is deficient in biocidal properties. Herein, we present green nanofibers with effective antibacterial and antiviral activities that can provide sustainable bioprotection by continuously producing reactive oxygen species (ROS). The superiority of the design is that the nanofibers can absorb and store visible light energy and maintain the activity under light or dark environment. Moreover, the nanofibers can uninterruptedly release ROS in the absence of an external hydrogen donor, acting as a biocide under all weather conditions. A facile spraying method is proposed to rapidly deploy the functional nanofibers to existing PPE, such as protective suits and masks. The modified PPE exhibit stable ROS production, excellent capacity for storing activity potential, long-term durability, and high bactericidal (>99.9%) and viricidal (>99.999%) efficacies.


Assuntos
Anti-Infecciosos/farmacologia , Hidrogênio/química , Luz , Nanofibras/química , Benzofenonas/química , Celulose/farmacologia , Nanofibras/ultraestrutura , Riboflavina/farmacologia
9.
Carbohydr Polym ; 260: 117807, 2021 May 15.
Artigo em Inglês | MEDLINE | ID: mdl-33712153

RESUMO

To date, the production of bacterial nanocellulose (BNC) by standard methods has been well known, while the use of low-cost feedstock as an alternative medium still needs to be explored for BNC commercialization. This study explores the prospect for the use of the different aqueous extract of fruit peel wastes (aE-FPW) as a nutrient and carbon source for the production of BNC. Herein, this objective was accomplished by the use of a novel, high- yielding strain, isolated from rotten apple and further identified as Komagataeibacter xylinus IITR DKH20 using 16 s rRNA sequencing analysis. The physicochemical properties of BNC matrix collected from the various aE-FPW mediums were similar or advanced to those collected with the HS medium. Statistical optimization of BNC based on Central Composite Design was performed to study the effect of significant parameters and the results demonstrated that the BNC yield (11.44 g L-1) was increased by 4.5 fold after optimization.


Assuntos
Acetobacteraceae/metabolismo , Celulose/metabolismo , Nanoestruturas/química , Acetobacteraceae/classificação , Acetobacteraceae/genética , Acetobacteraceae/isolamento & purificação , Celulose/química , Celulose/isolamento & purificação , Frutas/microbiologia , Malus/microbiologia , Microscopia de Força Atômica , Filogenia , RNA Ribossômico 16S/química , RNA Ribossômico 16S/isolamento & purificação , RNA Ribossômico 16S/metabolismo , Espectroscopia de Infravermelho com Transformada de Fourier
10.
Carbohydr Polym ; 260: 117814, 2021 May 15.
Artigo em Inglês | MEDLINE | ID: mdl-33712158

RESUMO

Lytic polysaccharide monooxygenases (LPMOs), monocopper enzymes that oxidatively cleave recalcitrant polysaccharides, have important biotechnological applications. Thermothelomyces thermophilus is a rich source of biomass-active enzymes, including many members from auxiliary activities family 9 LPMOs. Here, we report biochemical and structural characterization of recombinant TtLPMO9H which oxidizes cellulose at the C1 and C4 positions and shows enhanced activity in light-driven catalysis assays. TtLPMO9H also shows activity against xyloglucan. The addition of TtLPMO9H to endoglucanases from four different glucoside hydrolase families (GH5, GH12, GH45 and GH7) revealed that the product formation was remarkably increased when TtLPMO9H was combined with GH7 endoglucanase. Finally, we determind the first low resolution small-angle X-ray scattering model of the two-domain TtLPMO9H in solution that shows relative positions of its two functional domains and a conformation of the linker peptide, which can be relevant for the catalytic oxidation of cellulose and xyloglucan.


Assuntos
Celulases/metabolismo , Celulose/metabolismo , Ativação Enzimática/efeitos da radiação , Proteínas Fúngicas/metabolismo , Luz , Oxigenases de Função Mista/metabolismo , Sordariales/enzimologia , Biomassa , Catálise , Celulose/química , Proteínas Fúngicas/química , Proteínas Fúngicas/classificação , Proteínas Fúngicas/genética , Glucanos/química , Glucanos/metabolismo , Oxigenases de Função Mista/química , Oxigenases de Função Mista/classificação , Oxigenases de Função Mista/genética , Oxirredução , Filogenia , Domínios Proteicos , Proteínas Recombinantes/biossíntese , Proteínas Recombinantes/química , Proteínas Recombinantes/isolamento & purificação , Espalhamento a Baixo Ângulo , Estereoisomerismo , Especificidade por Substrato , Difração de Raios X , Xilanos/química , Xilanos/metabolismo
11.
Carbohydr Polym ; 260: 117816, 2021 May 15.
Artigo em Inglês | MEDLINE | ID: mdl-33712160

RESUMO

A biaxially stretched cellulose film with high performance was manufactured from ionic liquid solution through an environmentally friendly, cost effective and facile process. As the transverse stretching ratio (TSR) is increased, the tensile strength and elastic modulus of the biaxially stretched cellulose film in transverse direction (TD) are significantly improved and the coefficient of thermal expansion in TD is reduced while the performance achieves balance in the machine direction (MD) and TD. The transverse stretching regulates the microfibril orientation in the gel film from dominantly uniaxial orientation in MD to homogeneous planar orientation. This microfibril orientation may further play a role in the orientation of the chains in the films during gel drying as evidenced from the birefringence and 2D XRD results. These results indicate cellulose film prepared from ionic liquid process could be utilized with improved structural and mechanical properties by biaxial stretching, and thus serves in various applications.


Assuntos
Celulose/química , Líquidos Iônicos/química , Cristalização , Módulo de Elasticidade , Géis/química , Gossypium/metabolismo , Propriedades de Superfície , Resistência à Tração
12.
Carbohydr Polym ; 260: 117817, 2021 May 15.
Artigo em Inglês | MEDLINE | ID: mdl-33712161

RESUMO

While green bioplastic based on carbohydrate polymers have showed considerable promise, the methods typically used to prepare them in a single material have remained a significant challenge. In this study, a simple approach is proposed to fabricate high performance cellulose films composed of chemically and physically dual-crosslinked 2,2,6,6-tetramethylpiperidine-1-oxy-oxidized cellulose nanofibers (DC TEMPO-CNFs). The hydroxyl groups of TEMPO-CNF suspensions were firstly crosslinked chemically with epichlorohydrin (ECH), and subsequently TEMPO-CNF matrices were crosslinked physically via the strong electrostatic interaction between carboxylate and Ca2+ ions. It was found that the optimized DC TEMPO-CNF films exhibit a good transmittance (90 %) and a high tensile strength (303 MPa). Furthermore, these DC TEMPO-CNF films revealed superior thermal stability and excellent water resistance compared to neat TEMPO-CNF films without crosslinked domains. We believe that these results will pave the way to preparing practical polysaccharide bioplastics with simple, environmentally-friendly manufacturing processes.


Assuntos
Celulose/química , Nanofibras/química , Cálcio/química , Celulose Oxidada/química , Epicloroidrina/química , Íons/química , Piperidinas/química , Eletricidade Estática , Temperatura , Resistência à Tração , Água/química
13.
Carbohydr Polym ; 260: 117818, 2021 May 15.
Artigo em Inglês | MEDLINE | ID: mdl-33712162

RESUMO

Poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) is a conducting polymer frequently used with cellulose, to develop advanced electronic materials. To understand the fundamental interactions between cellulose and PEDOT:PSS, a quartz crystal microbalance with dissipation (QCM-D) was used to study the adsorption of PEDOT:PSS onto model films of cellulose-nanofibrils (CNFs) and regenerated cellulose. The results show that PEDOT:PSS adsorbs spontaneously onto anionically charged cellulose wherein the adsorbed amount can be tuned by altering solution parameters such as pH, ionic strength and counterion to the charges on the CNF. Temperature-dependent QCM-D studies indicate that an entropy gain is the driving force for adsorption, as the adsorbed amount of PEDOT:PSS increased with increasing temperature. Colloidal probe AFM, in accordance with QCM-D results, also showed an increased adhesion between cellulose and PEDOT:PSS at low pH. AFM images show bead-like PEDOT:PSS particles on CNF surfaces, while no such organization was observed on the regenerated cellulose surfaces. This work provides insight into the interaction of PEDOT:PSS/cellulose that will aid in the design of sustainable electronic devices.


Assuntos
Celulose/química , Poliestirenos/química , Tiofenos/química , Adsorção , Concentração de Íons de Hidrogênio , Microscopia de Força Atômica , Nanofibras/química , Concentração Osmolar , Técnicas de Microbalança de Cristal de Quartzo , Propriedades de Superfície , Temperatura
14.
Carbohydr Polym ; 260: 117820, 2021 May 15.
Artigo em Inglês | MEDLINE | ID: mdl-33712163

RESUMO

A high-performance flexible conductive substrate is one of the key components for developing promising wearable devices. Concerning this, a sustainable, flexible, transparent, and conductive cellulose/ZnO/AZO (CZA) film was developed in this study. The cellulose was used as the transparent substrate. The added AZO was as the conductive layer and ZnO functioned as an interface buffer layer. Results showed that the interface buffer layer of ZnO effectively alleviated the intrinsic incompatibility of organic cellulose and inorganic AZO, resulting in the improvement of the performance of CZA film. In compared with the controlled cellulose/AZO (CA) film with 365 Ω/sq sheet resistance and 87% transmittance, this CZA film featured a low conductive sheet resistance of 115 Ω/sq and high transmittance of 89%, as well as low roughness of 1.85 nm Moreover, the existence of conducive ZnO buffer layer enabled the conductivity of CZA film to be stable under the bending treatment. Herein, a flexible electronic device was successfully prepared with the biomass materials, which would be available by a roll-to-roll production process.


Assuntos
Celulose/química , Eletrônica , Alumínio/química , Condutividade Elétrica , Óxido de Zinco/química
15.
Carbohydr Polym ; 260: 117823, 2021 May 15.
Artigo em Inglês | MEDLINE | ID: mdl-33712164

RESUMO

A bio-based pressure-responsive sensor with adjustable structural color is prepared by combining aerogel skeleton of cellulose nanocrystals (CNCs)/poly(ethylene glycol) (PEG) obtained via the ice-templating method with flexible polyacrylamide (PAAM) elastomer. The white aerogel is composed of consecutive ribbons, demonstrating chiral nematic structure. These ribbons are rearranged to be vertical to the force direction, leading to immediate appearance of the structural color when the 3D aerogel transforms to a 2D plane. Helical pitches are regulated by the PEG content that the wavelength of structural color covers up to 178 nm. There is an excellent linear correlation between pressure and transmittance of reflectance peak, and the sensitivity to pressure can be regulated by changing solid content of PAAM. Furthermore, the pressure-responsive color is still vivid after 16 cycles of compression. This flexible material with pressure-responsive structural color is promising in sensing, intelligent display, information transmission, and etc.


Assuntos
Técnicas Biossensoriais/métodos , Géis/química , Pressão , Resinas Acrílicas/química , Celulose/química , Força Compressiva , Nanopartículas/química , Polietilenoglicóis/química
16.
Carbohydr Polym ; 260: 117840, 2021 May 15.
Artigo em Inglês | MEDLINE | ID: mdl-33712175

RESUMO

Highly efficient shielding materials with an excellent electromagnetic wave absorption have gained increased attention. A new design was used to provide cellulose paper with a high electromagnetic shielding effectiveness (EMI SE) and improve the absorption performance by constructing an asymmetry sandwich structure that consisted of a dense nickel coating, Fe3O4 nanoparticles and a porous nickel layer. This unique structure caused a "multiple reflection-absorb-reflection" process when the electromagnetic waves penetrated the sample. The EMI absorption (SEA) and total SE (SET) increased with Fe3O4 absorption time increasing at 8.2-12.4 GHz, which was attributed to the synergistic effect between porous nickel layer and Fe3O4 nanoparticles. The SEA and SET of the sample with a thickness of 0.195 mm can achieved 18.57 and 41.88 dB, respectively. The design was conducive to improving the magnetic and corrosion resistance properties. This study provided a novel path to obtain a low cost and lightweight electromagnetic shielding material that can reduce secondary radiation.


Assuntos
Celulose/química , Óxido Ferroso-Férrico/química , Níquel/química , Protetores contra Radiação/química , Condutividade Elétrica , Campos Eletromagnéticos , Magnetismo , Nanopartículas Metálicas/química , Porosidade , Propriedades de Superfície , Temperatura
17.
Molecules ; 26(4)2021 Feb 19.
Artigo em Inglês | MEDLINE | ID: mdl-33669556

RESUMO

Cyclodextrins (CDs) are a series of cyclic oligosaccharides formed by amylose under the action of CD glucosyltransferase that is produced by Bacillus. After being modified by polymerization, substitution and grafting, high molecular weight cyclodextrin polymers (pCDs) containing multiple CD units can be obtained. pCDs retain the internal hydrophobic-external hydrophilic cavity structure characteristic of CDs, while also possessing the stability of polymer. They are a class of functional polymer materials with strong development potential and have been applied in many fields. This review introduces the research progress of pCDs, including the synthesis of pCDs and their applications in analytical separation science, materials science, and biomedicine.


Assuntos
Celulose/química , Celulose/síntese química , Ciclodextrinas/química , Ciclodextrinas/síntese química , Pesquisa , Tecnologia Biomédica , Sistemas de Liberação de Medicamentos , Ciência dos Materiais , Modelos Moleculares
18.
Carbohydr Polym ; 260: 117345, 2021 May 15.
Artigo em Inglês | MEDLINE | ID: mdl-33712116

RESUMO

The biotechnological applications of cellulose nanocrystals (CNCs) continue to grow due to their sustainable nature, impressive mechanical, rheological, and emulsifying properties, upscaled production capacity, and compatibility with other materials, such as protein and polysaccharides. In this study, hydrogels from CNCs and pectin, a plant cell wall polysaccharide broadly used in food and pharma, were produced by calcium ion-mediated internal ionotropic gelation (IG). In the absence of pectin, a minimum of 4 wt% CNC was needed to produce self-supporting gels by internal IG, whereas the addition of pectin at 0.5 wt% enabled hydrogel formation at CNC contents as low as 0.5 wt%. Experimental data indicate that CNCs and pectin interact to give robust and self-supporting hydrogels at solid contents below 2.5 %. Potential applications of these gels could be as carriers for controlled release, scaffolds for cell growth, or wherever else distinct and porous network morphologies are required.


Assuntos
Celulose/química , Hidrogéis/química , Nanopartículas/química , Pectinas/química , Força Compressiva , Espalhamento a Baixo Ângulo , Temperatura , Difração de Raios X
19.
Carbohydr Polym ; 260: 117751, 2021 May 15.
Artigo em Inglês | MEDLINE | ID: mdl-33712121

RESUMO

The breakdown and buildup mechanisms in concentrated cellulose nanocrystal (CNC) suspensions under shear and during relaxation upon cessation of shear were accessed by small-angle X-ray and light scattering combined with rheometry. The dynamic structural changes over nanometer to micrometer lengthscales were related to the well-known three-regime rheological behavior. In the shear-thinning regime I, the large liquid crystalline domains were progressively fragmented into micrometer-sized tactoids, with their cholesteric axis aligned perpendicular to the flow direction. The viscosity plateau of regime II was associated to a further disruption into submicrometer-sized elongated tactoids oriented along the velocity direction. At high shear rate, regime III corresponded to the parallel flow of individual CNCs along the velocity direction. Upon cessation of flow, the relaxation process occurred through a three-step buildup mechanisms: i) a fast reassembling of the individual CNCs into a nematic-like organization established up to micrometer lengthscales, ii) a slower formation of oriented large cholesteric domains, and iii) their isotropic redistribution.


Assuntos
Celulose/química , Nanopartículas/química , Espalhamento a Baixo Ângulo , Difração de Raios X , Difusão Dinâmica da Luz , Cristais Líquidos/química , Reologia , Resistência ao Cisalhamento , Viscosidade
20.
Carbohydr Polym ; 260: 117760, 2021 May 15.
Artigo em Inglês | MEDLINE | ID: mdl-33712122

RESUMO

A transparent versatile cellulose platform film was prepared from Eucalyptus pulp in this work. Based on such cellulose platform, multifunctional cellulose films with ultraviolet-shielding, photochromism, and strong mechanical strength were fabricated via nucleophilic postmodification strategy by introducing a versatile spiropyran moiety into cellulose molecules. The fabricated cellulose films exhibited super-high transmittance up to 96% and performed notable ultraviolet-shielding capacity at 200-400 nm. Moreover, the photochromic performance of cellulose films with color changes could be clearly observed by the naked eyes, and the fluorescent blue could be excited. Besides, the tensile stress of multi-functional cellulose film was about 80 MPa, which was almost 8 times stronger than that of the commercial polyethylene film at the same thickness. It is noteworthy that these superior performances promote such a cellulose platform to be a versatile precursor for fabricating various multi-functional cellulose used in the fields of out-door coating, transparent packaging, optical screen,etc.


Assuntos
Celulose/química , Benzopiranos/química , Eucalyptus/metabolismo , Indóis/química , Nanocompostos/química , Nitrocompostos/química , Espectroscopia de Infravermelho com Transformada de Fourier , Protetores Solares/química , Propriedades de Superfície , Resistência à Tração , Raios Ultravioleta
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