Tuneable Permeability of Cellulose Nanofibrils‐based Membranes in Next‐Generation Barrier‐On‐Chip Systems

The use of nanocelluloses is being conducted for the most diverse applications. Their performance as coating agent has been mainly explored to improve barrier properties, as they emerge as perfect candidate for plastic substitution, but it is also important to explore their potential to improve printing quality. In the present work, the influence of different nanocelluloses, obtained through mechanical, enzymatic, TEMPO-mediated oxidation and carboxymethylation treatments, in the coating process and inkjet printability of office papers was assessed. The results revealed that the cellulose nanofibrils are better for printability than the microfibrils. But the size and charge of the former must be taken into account, since fibrils of very small size penetrate the paper structure, dragging the pigments from the surface, and very anionic nanofibrils can also have negative influence on the optical density. Besides, an interesting synergy between surface-sizing starch and the cellulose nanofibrils was found to occur as the latter closed the paper structure, which prevented starch from penetrating, while potentiating both of their positive effects on ink pigment entrapment. An additional study of characterization of inkjet pigments was also performed.

A GH5 hyperthermostable endoglucanase from the archaeon Pyrococcus horikoshii (Ph-GH5) and a commercial endoglucanase FR were used to treat bleached eucalyptus pulp (BEP) fibers to produce cellulose nanofibrils (CNFs) through subsequent microfluidization. Enzymatic treatments facilitated CNF production due to the reduced degree of polymerization (DP) of the fibers. SEM imaging indicated that FR reduced fiber DP drastically and resulted in much shorter fibers than with Ph-GH5, even at very low dosages (1 mg protein/g fiber) of FR treatment compared with a high dosage (10 mg protein/g fiber) of Ph-GH5. The fibers treated with FR were much more uniform in length perhaps due to the presence of exoglucanase and beta-glucosidase saccharifying short microfibers into glucose. TEM imaging indicated that Ph-GH5 produced longer and entangled CNFs than FR with the same number of microfluidization passes. However, the CNF diameters were approximately the same for all CNFs from enzyme-treated fibers using both endoglucanases at two dosages (1 or 10 mg protein/g fiber). CNFs produced from BEP fibers without enzymatic treatment showed larger diameters than those with enzymatic treatment.

This work investigated the redispersion and setting behavior of highly loaded (~ 18 wt.% solids in water) pastes of cellulose nanofibrils (CNFs) with carboxymethyl cellulose (CMC). A single-screw extruder was used to continuously process CNF + CMC pastes into cord. The adsorption of CMC onto the CNFs was assessed through zeta potential and titration which revealed a surface charge change of ~ 61% from − 36.8 mV and 0.094 mmol/g COOH for pure CNF to -58.1 mV and 0.166 mmol/g COOH for CNF + CMC with a CMC degree of substitution of 0.9. Dried CNFs with adsorbed CMC was found to be fully redispersible in water and re-extruded back into a cord without any difficulties. On the other hand, chemical treatment with hydrochloric acid, a carbodiimide crosslinker, or two wet strength enhancers (polyamide epichlorohydrin and polyamine epichlorohydrin) completely suppressed the dispersibility previously observed for dried-untreated CNF + CMC. Turbidity was used to quantify the level of redispersion or setting achieved by the untreated and chemically treated CNF + CMC in both water and a strong alkaline solution (0.1 M NaOH). Depending on the chemical treatment used, FTIR analysis revealed the presence of ester, N-acyl urea, and anhydride absorption bands which were attributed to newly formed linkages between CNFs, possibly explaining the suppressed redispersion behavior. Water uptake of the differently treated and dried CNF + CMC materials agreed with both turbidity and FTIR results. Graphic abstract

In this study, isolated cellulose from corncobs was oxidized using 2,2,6-tetramethyl-1-piperidinyl oxy (TEMPO) to produce cellulose nanofibrils. Cellulose nanofibrils were characterized by FTIR, PSA, and zeta potential to determine their chemical structure, particle size, and surface charge. Subsequently, the obtained cellulose nanofibrils were incorporated into the alginate matrix to produce composite beads. The effects of cellulose nanofibrils and alginate composition in composite beads were studied on the physical properties such as diameter size, morphology, drying rate, and swelling behavior. The result figures out a new chemical structure in the cellulose nanofibrils spectrum after the treatment process. The content of surface charges increases three times after the treatment process, from 0.2 to 0.64 mmol/g. The average size of cellulose nanofibril suspension particles was 153,4, with a polydispersity index of 0.044 (the nanofiber range). The zeta potential value is -46.3 mV, demonstrating the good stability and dispersibility of the cellulose nanofibril particles. The diameter of composite Alginate-Cellulose Nanofibril (AC) beads was reduced from 4.003 to 3.078 mm in AC20 by increasing the cellulose nanofibril concentration. The capacity of alginate beads to absorb water was 30% higher than that of the composite AC beads. Based on SEM analysis, the morphology of AC beads was found to be finer and denser than that of alginate beads. The swelling kinetics of the beads indicate that the diffusion mechanism is a Fickian diffusion mechanism. Furthermore, cellulose nanofibril-added beads can potentially be used as smart materials in bioactive encapsulated applications owing to having good swelling properties.

Porosity, density and mechanical properties of the paper of steam exploded bamboo microfibers controlled by nanofibrillated cellulose

In this study, cellulose nanofibrils (CNFs) were successfully isolated from coconut palm petiole residues falling off naturally with chemical pretreatments and mechanical treatments by a grinder and a homogenizor. FTIR spectra analysis showed that most of hemicellulose and lignin were removed from the fiber after chemical pretreatments. The compositions of CNFS indicated that high purity of nanofibrils with cellulose contain more than 95% was obtained. X-ray diffractogram demonstrated that chemical pretreatments significantly increased the crystallinity of CNFs from 38.00% to 70.36%; however, 10-15 times of grinding operation followed by homogenizing treatment after the chemical pretreatments did not significantly improve the crystallinity of CNFs. On the contrary, further grinding operation could destroy crystalline regions of the cellulose. SEM image indicated that high quality of CNFs could be isolated from coconut palm petiole residues with chemical treatments in combination of 15 times of grinding followed by 10 times of homogenization and the aspect ratio of the obtained CNFs ranged from 320 to 640. The result of TGA-DTG revealed that the chemical-mechanical treatments improved thermal stability of fiber samples, and the CNFs with 15 grinding passing times had the best thermal stability. This work suggests that the CNFs can be successfully extracted from coconut palm petiole residues and it may be a potential feedstock for nanofiber reinforced composites due to its high aspect ratio and crystallinity.

Cellulose nanofibrils as reinforcing agents for PLA-based nanocomposites: An in situ approach

In this work, bagasse pulp was used to prepare cellulose nanofibrils (CNFs) by enzymatic assisted mechanical treatment. A xylanase pretreatment was applied for varying the hemicellulose content in the pulp fibers, and the contribution of this pretreatment to the post-mechanical treatment was investigated. The results showed that CNFs prepared after xylanase pretreatment exhibited enhanced thermal stability with an increase in crystallinity. However, the overall thermal stability of the CNFs decreased significantly after xylanase was applied directly to the mechanical treated CNFs. The results indicate that the presence of hemicellulose in the fiber could affect the thermal stability of CNFs. The direct application of xylanase to CNFs could affect both the hydrogen bond between the hemicellulose and the cellulose and the covalent bond between the hemicellulose molecules, which partially destroys the internal network structure and reduces of thermal stability of CNFs.

Cellulose nanofibril (CNF) is a class of promising and renewable nanocellulosic material due to its unique dimensional characteristics and appealing properties. CNF preparations based on TEMPO pretreatment followed by high-pressure homogenization have been studied intensively, while the high energy consumption and the environmental issues remain challenges to their application. Mechanical refining processes have been commonly applied at the academic and industrial relevant scales for CNF production. In this study, bleached softwood kraft pulp was subjected to high-efficiency wet ball milling (following enzymatic pretreatment) and mechanical grinding to obtain CNF. The effects of ball milling time, grinding gap, and grinding passes on structure and properties of CNF were evaluated. Scanning electron microscopy images confirmed that the diameter of CNF was decreased with the increment of ball milling time and number of grinding passes. The results indicated that ball milling time, grinding gap, and grinding passes were important to increase the dispersity of CNF suspensions. The degree of polymerization and crystallinity index of CNF decreased with increasing ball milling time and grinding passes.

Ultrasound-assisted extraction of bioactives as a strategic step for chemical pretreatments in nanocellulose production from acerola by-products

The application of nanocellulose has been adapted as fillers in composite bricks. Raw kenaf and oil palm empty fruit bunch were treated through chemical treatment and high intensity ultrasonication process to produce cellulose nanofibrils (CNF). One control brick without CNF and ten CNF composite bricks were fabricated. The composite bricks used different amount of CNF which were 40 - 200 ml mixed with filtered sand, portland cement and pebbles. Physical and mechanical characterization was done by using field emission scanning electron microscopy (FESEM) and universal testing machine (UTM) on CNF and composite bricks. FESEM showed the fibril diameter were ranges from 30 - 80 nm for kenaf and 20 - 60 nm for oil palm. The compression tests showed that control brick, 40 ml kenaf CNF composite brick and 40 ml oil palm CNF composite brick were cracked at force 39.01 kN, 50.46 kN and 42.16 kN respectively. Kenaf CNF composite brick has the highest value of Young’s Modulus which is 28.92 N/mm2, followed by oil palm CNF composite brick with 27.8 N/mm2 and control brick (Malaysia Standard) with 25.8 N/mm2. Kenaf and oil palm CNF can increase the strength of the bricks because of enhancement in their mechanical properties.

Cellulose nanofibrils reinforced xylan-alginate composites: Mechanical, thermal and barrier properties

Emulsion stabilization is a broad and relevant field with applications in oil, polymer and food industries. In recent years, the use of solid particles to stabilize emulsions or Pickering emulsions have been studied for their kinetic and physical properties. Nanomaterials derived from natural sources are an interesting alternative for this application. Cellulose nanofibrils (CNFs) have been widely explored as a Pickering emulsifier with potential food applications, however, in some cases the presence of surfactants is unavoidable, and the literature is devoid of an evaluation of the effect of a non-ionic food-grade surfactant, such as polysorbate 80, in the stabilization of a vegetable oil by CNFs. To better assess the possible interactions between CNFs and this surfactant emulsions containing coconut oil, an emerging and broadly used oil, were processed with and without polysorbate 80 and evaluated in their qualitative stability, morphological and physical properties. Fluorescence microscopy, dynamic light scattering and rheology were used for this assessment. Results indicate in absence of the surfactant, emulsion stability increased at higher CNFs content, creaming was observed at 0.15 and 0.3 wt.% of CNFs, while it was not evidenced when 0.7 wt.% was used. After the addition of surfactant, the droplets are covered by the surfactant, resulting in particles with a smaller diameter, entrapped in the cellulosic structure. Rheology indicates a lower network stiffness after adding polysorbate 80.

The recent decade has witnessed a growing demand to substitute synthetic materials with naturally-derived platforms for minimizing their undesirable footprints in biomedicine, environment, and ecosystems. Among the natural materials, cellulose, the most abundant biopolymer in the world with key properties, such as biocompatibility, biorenewability, and sustainability has drawn significant attention. The hierarchical structure of cellulose fibers, one of the main constituents of plant cell walls, has been nanoengineered and broken down to nanoscale building blocks, providing an infrastructure for nanomedicine. Microorganisms, such as certain types of bacteria, are another source of nanocelluloses known as bacterial nanocellulose (BNC), which benefit from high purity and crystallinity. Chemical and mechanical treatments of cellulose fibrils made up of alternating crystalline and amorphous regions have yielded cellulose nanocrystals (CNC), hairy CNC (HCNC), and cellulose nanofibrils (CNF) with dimensions spanning from a few nanometers up to several microns. Cellulose nanocrystals and nanofibrils may readily bind drugs, proteins, and nanoparticles through physical interactions or be chemically modified to covalently accommodate cargos. Engineering surface properties, such as chemical functionality, charge, area, crystallinity, and hydrophilicity, plays a pivotal role in controlling the cargo loading/releasing capacity and rate, stability, toxicity, immunogenicity, and biodegradation of nanocellulose-based delivery platforms. This review provides insights into the recent advances in nanoengineering cellulose crystals and fibrils to develop vehicles, encompassing colloidal nanoparticles, hydrogels, aerogels, films, coatings, capsules, and membranes, for the delivery of a broad range of bioactive cargos, such as chemotherapeutic drugs, anti-inflammatory agents, antibacterial compounds, and probiotics. SynopsisEngineering certain types of microorganisms as well as the hierarchical structure of cellulose fibers, one of the main building blocks of plant cell walls, has yielded unique families of cellulose-based nanomaterials, which have leveraged the effective delivery of bioactive molecules.

Tunable, thiol-ene, interpenetrating network hydrogels of norbornene-modified carboxymethyl cellulose and cellulose nanofibrils