Modified Cellulose Nanofibers Research Articles

Modification and characterization of a novel and fluorine-free cellulose nanofiber with hydrophobic and oleophobic properties

In this study, a brand-new, easy, and environmentally friendly approach for chemically functionalizing 2,2,6,6-tetramethylpiperidinyloxyl radical (TEMPO)-oxidized cellulose nanofiber (TOCNF) to produce modified cellulose nanofiber (octadecylamine-citric acid-CNF) was proposed. Effects of octadecylamine (ODA)/TOCNF mass ratio on the chemical structure, morphology, surface hydrophobicity and oleophobicity were studied. According to Fourier transform infrared spectroscopy (FTIR) analysis, ODA was successfully grafted onto the TOCNF by simple citric acid (CA) esterification and amidation reactions. Scanning electron microscopy (SEM) showed that a new rough structure was formed on the ODA-CA-CNF surface. The water contact angle (WCA) and the castor oil contact angle (OCA) of the ODA-CA-CNF reached 139.6° and 130.6°, respectively. The high-grafting-amount ODA-CA-CNF was sprayed onto paper, and the OCA reached 118.4°, which indicated good oil-resistance performance. The low-grafting-amount ODA-CNF was applied in a pH-responsive indicator film, exhibiting a colour change in response to the pH level, which can be applied in smart food packaging. The ODA-CA-CNF with excellent water/oil-resistance properties and fluorine-free properties can replace petrochemical materials and can be used in the fields of fluorine-free oil-proof paper.

A High-Proton Conductivity All-Biomass Proton Exchange Membrane Enabled by Adenine and Thymine Modified Cellulose Nanofibers.

Nanocellulose fiber materials were considered promising biomaterials due to their excellent biodegradability, biocompatibility, high hydrophilicity, and cost-effectiveness. However, their low proton conductivity significantly limited their application as proton exchange membranes. The methods previously reported to increase their proton conductivity often introduced non-biodegradable groups and compounds, which resulted in the loss of the basic advantages of this natural polymer in terms of biodegradability. In this work, a green and sustainable strategy was developed to prepare cellulose-based proton exchange membranes that could simultaneously meet sustainability and high-performance criteria. Adenine and thymine were introduced onto the surface of tempo-oxidized nanocellulose fibers (TOCNF) to provide many transition sites for proton conduction. Once modified, the proton conductivity of the TOCNF membrane increased by 31.2 times compared to the original membrane, with a specific surface area that had risen from 6.1 m²/g to 86.5 m²/g. The wet strength also increased. This study paved a new path for the preparation of environmentally friendly membrane materials that could replace the commonly used non-degradable ones, highlighting the potential of nanocellulose fiber membrane materials in sustainable applications such as fuel cells, supercapacitors, and solid-state batteries.

Tailored lipid crystallization in confined microparticle domains through alkyl chains infiltration from cellulose nanofiber surfactants

Through this study, we show that hydrophobically modified cellulose nanofibers can substantially influence the subcell crystallization of ceramide-based lipids within confined particle domains. We demonstrate that C18 alkyl chain-conjugated bacterial cellulose nanofibers (BCNFC18) can armor ceramide (Cer)/stearyl alcohol (SA) lipid crystal phases to form ceramide-based lipid microparticles (CerMPs). X-ray diffraction measurements revealed that by armoring CerMPs with BCNFC18, lipid crystal structures could be changed from the β subcell to β’ subcell. Less generation of β subcells within a densely packed lipid crystal structure is critically important to confine the growth of Cer/SA lipid crystals within a microparticle domain. By performing energy calculations and interfacial rheology analysis, we found that the alkyl chains of BCNFC18 infiltrated the CerMP peripheries. We demonstrate through this study that the alkyl chains of BCNFC18 can associate with the highly crystalline Cer/SA crystal phase of a lipid, thereby strengthening the interface between the lipid and the BCNFC18. The study findings highlight the importance of engineering nanoscale fiber surfactants capable of alkyl chain infiltration. These surfactants can be used to prepare crystallizable active ingredients in a feasible and diverse manner for applications in the pharmaceutical, food, and cosmetic industries.

Biobased hydrogel reinforced with wastepaper-derived modified cellulose nanofiber as an efficient dye remover from wastewater

Biobased hydrogel reinforced with wastepaper-derived modified cellulose nanofiber as an efficient dye remover from wastewater

Biobased biodegradable hydrogel containing modified cellulosic nanofiber-ZnO nanohybrid as efficient metal ions removers with recyclable capacity

In the past decades, immense attention has been paid to the development of biobased hydrogel nanocomposite (HNC) to remove metal ions from wastewater owing to their high adsorption capacity, biodegradability, and reusability. In this work, we have demonstrated the fabrication of a nanohybrid using modified cellulose nanofiber and zinc oxide nanoparticles using an eco-friendly and non-toxic approach and subsequently incorporated it into a starch/itaconic acid/acrylic acid-based hydrogel matrix. The structure and morphology of the prepared nanohybrid and HNC were characterized by different spectroscopic and microscopic techniques. The resulting HNCs were employed for the removal of metal ions (Cu(II) and Fe(II)) from aqueous solution and manifested noteworthy adsorption ability. With the incorporation of 0.25 wt% nanohybrid, the HNC showed the highest water swelling capacity of 580 g/g. Besides, the incorporation of the nanohybrid enhanced the metal ion adsorption ability of the HNC, and the removal capacity of 122 and 70 mg/g was obtained for Cu(II) and Fe(II) ions, respectively. The adsorption kinetics followed the pseudo-second-order model and isotherms were found to be fitted well with the Freundlich model. Additionally, the prepared nano-structural adsorbent can be removed easily and could be used for 3 repeated purification cycles without significant loss of efficiency. Thus, this work leads to the development of nanohybrid-containing biobased HNC as a promising candidate for the removal of toxic metal ions with remarkable reusability as well as adsorption capacity.

Preparation and environmental analysis of biodegradable polylactic acid and modified cellulose nanofiber composites

Polylactic acid (PLA) and cellulose nanofibers (CNFs) show promise as bio-based alternatives to non-degradable plastics, which pose environmental challenges. Yet, CNFs' hydrophilicity hampers their dispersion in hydrophobic PLA. This study modifies CNF surfaces with diisocyanate compounds to create hydrophobic isocyanate-modified CNFs (mCNFs), enhancing their compatibility with PLA. One isocyanate of the diisocyanate compound is grafted onto the surface of CNF and the isocyanate content varied by adjusting grafting reaction time. PLA-mCNF composites are produced by a twin-screw extruder and show improved mechanical properties and biodegradability compared to pristine PLA and PLA-unmodified CNF composite. The environmental impacts of PLA-mCNF composites are evaluated using a life-cycle assessment method and compared to corn grain-based PLA. The optimized PLA-mCNF composite (6 h of grafting reaction) has lower environmental impacts than corn grain-based PLA, with global warming and fossil resource scarcity of 3.021 kg eq and 0.813 kg oil eq, respectively. This study underscores the feasibility of optimizing PLA composite properties by employing a small proportion of toxic diisocyanate on CNF surfaces. The findings highlight the potential of such modified composites to offer improved sustainability and performance characteristics, contributing to the development of eco-friendly materials.

Multifunctional composite films based on polyvinyl alcohol, quaternary ammonium salt modified cellulose nanofibers and tannic acid-iron ion coordination complexes for food packaging

The development of sustainable and well-performing food packaging materials takes on critical significance, whereas it is still challenging. To overcome the shortcomings of polyvinyl alcohol (PVA) as a degradable packaging material, in this work, hydrophobic quaternary ammonium salt (QAS) modified cellulose nanofibers (CNF) and tannic acid‑iron ion coordination complexes (TA-Fe) were adopted for the preparation of functional PVA films. The modified CNF (CNF-QAS) not only improved the mechanical properties and water resistance of PVA, but also endowed it with antibacterial ability. In addition, the synergistic antibacterial capability with CNF-QAS was achieved using TA-Fe with photothermal therapy. As a result, the modulus, elongation at break, tensile strength, and water contact angle of the prepared PVA films were examined as 88 MPa, 200 %, 11.7 MPa, and 94.8°, respectively. Furthermore, with the assistance of CNF-QAS and TA-Fe, the films inhibited the growth of E. coli and S. aureus by 99.8 % and 99.7 %, respectively, and they exhibited high cell viability of 90.5 % for L929 fibroblasts. Based on the above encouraging properties, the functional PVA films could significantly extend the shelf life of oranges for over two weeks, proving the excellent application prospects in the food packaging field.

Strong Bioactive Glass-Based Hybrid Implants with Good Biomineralization Activity Used to Reduce Formation Duration and Improve Biomechanics of Bone Regeneration.

Developing bioactive implants with strong mechanical properties and biomineralization activity is critical in bone repair. In this work, modified cellulose nanofiber (mCNF)-reinforced bioactive glass (BG)-polycaprolactone (PCL) hybrids (mCNF-BP) with strong biomechanics and good apatite formation ability were reported. Incorporating mCNFs shortens the forming duration of the hybrid films and enhances the biomechanical performance and in vitro apatite-formation capability. The optimized biomechanical performance of the optimal hybrid materials is produced at a relatively high mCNF content (1.0 wt%), including a considerably higher modulus of elasticity (948.65 ± 74.06 MPa). In addition, the biomineralization activity of mCNF-BP hybrids is also tailored with the increase in the mCNF contents. The mCNF-BP with 1.5 wt% and 2.0 wt% mCNFs demonstrate the best biomineralization activity after immersing in simulated body fluid for 3 days. This study suggests that mCNFs are efficient bioactive additive to reinforce BG-based hybrids' mechanical properties and biomineralization activity.

Tough and strong sustainable thermoplastic elastomers nanocomposite with self-assembly of SI-ATRP modified cellulose nanofibers

The ingenious design of sustainable thermoplastic elastomers (STPEs) is of great significance for the goal of the sustainable development. However, the preparation of STPEs with good mechanical performance is still complicated and challenging. Herein, to achieve a simple preparation of STPEs with strong mechanical properties, two biobased monomers (tetrahydrofurfuryl methacrylate (THFMA) and lauryl methacrylate (LMA)) were copolymerized into poly (THFMA-co-LMA) (PTL) and grafted onto TEMPO oxidized cellulose nanofiber (TOCN) via one-pot surface-initiated atom transfer radical polymerization (SI ATRP). The grafting modified TOCN could be self-assembled into nano-enhanced phases in STPEs, which are conducive to the double enhancement of the strength and toughness of the STPEs, and the size of nano-enhanced phases is mainly affected by TOCN fiber length and molecular weight of grafting chains. Especially, with the addition of 7 wt% TOCN, tensile strength, tensile strain, toughness, and glass transition temperature (Tg) of TOCN based STPEs (TOCN@PTL) exhibited 140 %, 36 %, 215 %, and 6.8 °C increase respectively, which confirmed the leading level in the field of bio-based elastomers. In general, this work constitutes a proof for the chemical modification and self-assembly behavior of TOCN by one-pot SI ATRP, and provides an alternative strategy for the preparation of high-performance STPEs.

Luminescent 3D printed poly(lactic acid) nanocomposites with enhanced mechanical properties

AbstractThe three‐dimensional (3D) printing of functional composite materials has gained tremendous interest in recent years. Nevertheless, research on 3D printing of luminescent composite materials is very limited, and the mechanical properties of such 3D‐printed composites are poor. Herein, we report the preparation and characterization of a poly(lactic acid) (PLA) composite that, when 3D printed, exhibits enhanced toughness and high solid‐state fluorescence quantum yield. Incorporation of only 1 wt% pyrene butyric acid modified cellulose nanofibers (PBA‐m‐CNF) and l0 wt% thermoplastic polyurethane (TPU) into PLA led to 223% increase in toughness and 21% increase in tensile modulus of PLA. Scanning electron microscopy (SEM) and X‐ray microcomputed tomography (μ‐CT) analysis of the fractured cross‐sections of 3D printed composites revealed a ductile failure mode. The PLA/PBA‐m‐CNF1/TPU10 3D printed composite also exhibited a high solid‐state fluorescence quantum yield of 38.35%. To the best of our knowledge, this is the first report to show both enhanced mechanical properties and high solid‐state fluorescence emission for 3D printable PLA. Such functional PLA composites could have potential applications in the fabrication of complex‐shaped sensors, optical light pipes, etc.

Transparent nanopaper from nanofibrillated bamboo pulp

Bamboo pulp was used to produce modified cellulose nanofiber (M-CNF) with 3,4-dichlorophenyl isocyanate through a one-step mechano-chemical method by ball milling. The structural variations of bamboo cellulose with different degrees of substitution (DS) for hydroxyl groups were studied by FTIR, XRD, TEM, AFM, and elemental analysis. The DS was as high as 0.88 after just 2 h of ball milling, and the diameter of M-CNF was 2 to 3 nm after just 1 h of ball milling. The modified nanocellulose was hydrophobic, with a water contact angle as high as 87°. The nanopaper made from the nanocellulose by vacuum filtration was transparent, with an optical transparence up to 88.8% at 550 nm. However, the transmittance of the modified nanopaper decreased to nearly 0 over the wavelength range of 200 to 300 nm. This nanopaper can be used as flexible optoelectronic material, packing material, or ultraviolet shielding material.

Rapid adsorption of directional cellulose nanofibers/3-glycidoxypropyltrimethoxysilane/polyethyleneimine aerogels on microplastics in water

Currently, cellulose-based aerogel materials are a hot topic owing to their high specific surface area and high porosity, as well as the green, degradable and biocompatible characteristics of cellulosic materials. Modification of cellulose to enhance the adsorption properties of cellulose-based aerogels has important research significance in solving the problem of water body pollution. In this paper, cellulose nanofibers (CNFs) were modified with polyethyleneimine (PEI), and modified aerogels with directional structures were prepared by a simple reaction and freeze-drying method. The adsorption behavior of the aerogel followed the adsorption kinetic models and isotherm models. More significantly, the aerogel could rapidly adsorb microplastics, reaching equilibrium within 20 min. Furthermore, the fluorescence displayed directly expresses the occurrence of the adsorption behavior of the aerogels. Therefore, the modified cellulose nanofiber aerogels were of reference significance for microplastic removal from water bodies.

Modeling of Hexavalent Chromium Removal with Hydrophobically Modified Cellulose Nanofibers.

Cellulose nanofibers (CNF) are sustainable nanomaterials, obtained by the mechanical disintegration of cellulose, whose properties make them an interesting adsorbent material due to their high specific area and active groups. CNF are easily functionalized to optimize the performance for different uses. The hypothesis of this work is that hydrophobization can be used to improve their ability as adsorbents. Therefore, hydrophobic CNF was applied to adsorb hexavalent chromium from wastewater. CNF was synthetized by TEMPO-mediated oxidation, followed by mechanical disintegration. Hydrophobization was performed using methyl trimetoxysilane (MTMS) as a hydrophobic coating agent. The adsorption treatment of hexavalent chromium with hydrophobic CNF was optimized by studying the influence of contact time, MTMS dosage (0–3 mmol·g−1 CNF), initial pH of the wastewater (3–9), initial chromium concentration (0.10–50 mg·L−1), and adsorbent dosage (250–1000 mg CNF·L−1). Furthermore, the corresponding adsorption mechanism was identified. Complete adsorption of hexavalent chromium was achieved with CNF hydrophobized with 1.5 mmol MTMS·g−1 CNF with the faster adsorption kinetic, which proved the initial hypothesis that hydrophobic CNF improves the adsorption capacity of hydrophilic CNF. The optimal adsorption conditions were pH 3 and the adsorbent dosage was over 500 mg·L−1. The maximum removal was found for the initial concentrations of hexavalent chromium below 1 mg·L−1 and a maximum adsorption capacity of 70.38 mg·g−1 was achieved. The kinetic study revealed that pseudo-second order kinetics was the best fitting model at a low concentration while the intraparticle diffusion model fit better for higher concentrations, describing a multi-step mechanism of hexavalent chromium onto the adsorbent surface. The Freundlich isotherm was the best adjustment model.

Hexavalent Chromium Sorption by Modified Cellulose Macro and Nanofibers Obtained from Eucalyptus Residues

Hexavalent Chromium Sorption by Modified Cellulose Macro and Nanofibers Obtained from Eucalyptus Residues

Adsorption of small size microplastics based on cellulose nanofiber aerogel modified by quaternary ammonium salt in water

Due to severe water pollution and water shortage, research on biomass adsorbent materials with high adsorption capacity for microplastics in water is one of the effective methods to control and solve water pollution. In this paper, cellulose nanofibers (CNF) were selected as the matrix material, 2, 3-epoxypropyl trimethyl ammonium chloride (EPTMAC) as a modifier, and polyvinyl alcohol (PVA) as a crosslinking agent were used to prepare the modified cellulose nanofibers aerogel with directional structure by liquid nitrogen freezing method, which was used for the adsorption of small size microplastics in water. The modified aerogel has a good adsorption capacity of 146.38 mg/g for small size microplastics, and the adsorption behavior of aerogel conforms to Langmuir isotherm and pseudo-first-order and pseudo-second-order adsorption kinetics model. Meanwhile, the fluorescence characteristics show that the adsorption behavior occurred. In addition, the modified aerogel still maintains good adsorption capacity under different influence factors. Therefore, modified cellulose nanofibers aerogel has a broad application prospect in the field of removing microplastics from water.

Selective Localization of Nanofiller on Mechanical Properties of Poly(lactic acid)/Poly(butylene adipate-co-terephthalate) Nanocomposites via the Surface Energy and Melt Blending Technique

The dispersion and localization of nanofillers at the interface in immiscible polymer blends to prevent phase separation and voids are the most important factors for fabricating nanocomposites with outstanding mechanical properties. However, these factors are limited to conventional industrial applications, such as melt blending and extrusion due to the aggregation/agglomeration of the nanofillers during processing. Here, the effects of the melt blending technique and nanofiller surface energy on dispersion and selective localization of the nanofillers in poly(lactic acid) (PLA)/poly(butylene adipate-co-terephthalate) (PBAT) nanocomposite were studied. Consequently, we confirmed that the localization of modified silica (m-SiO2) in the nanocomposite could be determined by controlling the PBAT mixing time. Furthermore, the m-SiO2, located at the PLA/PBAT interface with modified cellulose nanofiber, improved the morphology of the PLA/PBAT nanocomposites, thereby significantly improving the tensile strength and elongation at break by approximately 7% and 16%, respectively. The results of this study demonstrate a novel approach to control the dispersion and localization of nanofillers in immiscible polymer blends, thereby paving a new possibility to fabricate eco-friendly packaging materials industrially.

Mechanical and electrochemical properties of UV-curable nanocellulose/urushiol epoxy acrylate anti-corrosive composite coatings

A novel urushiol epoxy acrylate (UEA) photosensitive prepolymer was synthesized. In order to realize the curing of UEA, modified cellulose nanofiber photoinitiators (MCNFI) were prepared through the modification of cellulose nanofiber (CNF). Then UV-curable MCNFI/UEA composite coatings were fabricated, and their structures, mechanical and electrochemical properties were investigated. The results showed that the studied properties of MCNFI/UEA coating were superior to those of pure UEA and unmodified CNF reinforced UEA (CNF/UEA) coating. The optimum mechanical properties were achieved at 8 wt% loading level, after which further loading of MCNFI resulted in the reduction in mechanical properties. The enhanced mechanical properties should be attributed to the structural characteristics of UEA matrix containing appropriate soft and hard segments, the good dispersibility and interfacial interaction of the fillers within UEA matrix. Besides, MCNFI (8 wt%)/UEA coating exhibited the most pronounced anti-corrosive performance. This paper demonstrated a novel preparation method of renewable urushiol based anti-corrosive coating using modified nanocellulose as macrophotoinitiator and filler simultaneously.

Modified cellulose nanofibers aerogels as a novel air filters; Synthesis and performance evaluation

Nanofilters made with high adsorption freeze-dried modified cellulose nanofiber (CNF) aerogel were produced. The modification was made using functional groups containing phthalimide, and then their ability to adsorb particulate matter (PM) was evaluated and compared with the control filter (HEPA). The results showed that the highest adsorption of PM2.5 (99.95%) belonged to the nanofilters made of 1.5% phthalimide-modified CNF aerogel, and the lowest adsorption (76.66%) was related to the control samples. Moreover, based on the results, the nanofilter produced from freeze-dried phthalimide-modified CNF aerogel showed high filtration efficiency as well as excellent resistance to temperature and humidity. This modification enables the filter to operate in different environmental conditions, especially for particles less than 0.1 μm that are mainly responsible for reducing air quality, human health, air visibility, and climate change. In conclusion, we developed an environmentally friendly biodegradable nanofilter capable of high-performance filtration functions and structural stability in different environmental conditions.

Antioxidant and antimicrobial modified cellulose nanofibers for food applications

Cellulose nanofibers (CNF) are renewable, biodegradable, and non-toxic biopolymers; however, they have not been widely adopted as an additive by the food industry. In this study, CNF functionality was improved through chemical modification. Antioxidant and antimicrobial nanofibers were produced through the esterification of CNF with phenolic acids. CNF were esterified with vanillic or cinnamic acid using two different esterifying agents: thionyl chloride and 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide (EDC). Modified fibers from the four different treatments were evaluated for their structural properties, antioxidant properties, thermal stability, dispersibility and antimicrobial properties. Both esterifying agents successfully produced phenolic acid esterified CNF fibers. Vanillic acid modified fibers showed better antioxidant activity (70% DPPH radical scavenging activity) than cinnamic acid modified fibers (10% DPPH scavenging activity). In contrast, cinnamic acid modified fibers showed better antimicrobial activity against Staphylococcus epidermidis. Thermal stability depended on the esterifying agent utilized; the use of thionyl chloride (DTG max 260.19 ± 1.38 °C) significantly (p < 0.05) reduced the thermal stability of modified fibers while EDC (DTG max 326.09 ± 0.49 °C) did not. When the modified CNF fibers were added to a model food (canola oil), a significant effect (p < 0.05) on lipid oxidation during storage depending on the type of CNF fiber used was observed. When compared to CNF, EDC modified fibers improved the oxidative stability of the canola oil while thionyl chloride modified fibers did not. These results suggest that esterification with phenolic acids can impart antimicrobial and antioxidant functionality to CNF food additives that have the potential to prolong the shelf life of foods.

Novle layered boron nitride nanosheets/cellulose nanofibers/epoxy composite with high thermal conductivity

Studies have shown that the construction of a three-dimensional interconnected filler network is an effective method to improve the thermal conductivity of the through-plane under a lower filler load. However, huge challenges still exist in building a long-range layered filler network and reducing the thermal resistance resulting from contact between fillers and matrix. In this work, boron nitride nanosheets (BNNSs) were proposed to be connected with modified cellulose nanofibers (CNFs) to obtain a long-range layered structure filler skeleton by bidirectional freezing orientation. Then epoxy resin was dipped under vacuum condition to prepare composite with thermal conductivity up to 1.43 W/mK in through-plane when filler content is 4.3 vol%, and the composite had low thermal expansion coefficient of 64.1 ppm/°C and excellent volume resistivity up to 3.7 × 1012 Ω cm at the same time.