Hydrophilic Nanocellulose Research Articles

Preparation of Janus film for fog water collection via layer-by-layer assembling of nanocellulose and nanochitin on PLA

In order to explore the possibility of natural carbohydrate polymers as a biodegradable and sustainable fog water harvesting material, this work proposed an efficient substrate (hydrophobic)-transition layer (amphoteric)-coating (hydrophilic) sandwich spin-coating strategy to form all biomass-based Janus film. The oxalic acid hydrolyzed nanochitin (OAChN) was applied as a transition layer that enabled successful spin-coating of the hydrophilic nanocellulose (TEMPO-oxidized cellulose nanofiber, TOCN) and nanochitin (partially deacetylated chitin nanofibers, DEChN) on the hydrophobic polylactic acid (PLA) film substrate. In which a layer-by-layer (LBL) assembling of TOCN (carboxyl-rich negative surface charge) and DEChN (amino-rich positive surface charge) was designed to form a thickness and surface property controllable polysaccharide coating on PLA. The finally formed PLA-OAChN-TOCN/DEChN (LBL) film showed hydrophilic and hydrophobic heteromeric faces at the opposite sides and thus had improved fog water collection capacity of 90.85 mg·cm−2·h−1 (30 layers of TOCN/DEChN spin-coated on PLA), which was 276 % higher than the pure PLA film. The transition layer engaged sandwich spin-coating strategy, together with LBL assembling method proposed in this study provided a feasible fabrication of all biomass-based fog water collectors (FWC) that could contribute to alleviating water shortage.

Utilization of different wood-based microfibril cellulose for the preparation of reinforced hydrophobic polymer composite films via Pickering emulsion: A comparative study

Pickering emulsion is a promising strategy for the preparation of hydrophobic polymer composite using hydrophilic nanocellulose. Herein, two types of microfibril cellulose, pure mechanical pretreated microfibril cellulose (P-MFC) and Deep eutectic solvents pretreated microfibril cellulose (DES-MFC), were used to fabricate reinforced hydrophobic polystyrene (PS) composites (MFC/PS) with the aid of Pickering emulsion. The results showed that both oil/water ratio and the content as well as surface hydrophilicity of MFC were playing an important role in emulsifying capacity. 8 % MFC/PS emulsion showed the smallest and most uniform emulsion droplets which is similar to nanofibril cellulose (NFC)/PS at the oil/water ratio of 3:1. The mechanical performance of MFC/PS composites verified that the reinforcement effect was closely related to the emulsifying capacity of MFC. Specially, when the content of P-MFC was 8 wt%, the composite exhibited the best mechanical properties with the tensile strength of 44.7 ± 4.4 MPa and toughness of 1162 ± 52.8 kJ/m3 and Young's modulus of 13.5 ± 0.8 GPa, which was comparable to NFC/PS composite. Moreover, the effective enhancement role of P-MFC in hydrophobic polymethyl methacrylate and polycarbonate composites were also realized via Pickering emulsion strategy. Overall, this work constituted a proof of concept of the potential application of P-MFC in nano-reinforced hydrophobic composite.

A Nanostructured Moisture‐Absorbing Gel for Fast and Large‐Scale Passive Dehumidification (Adv. Mater. 17/2022)

Dehumidification Dehumidification is significant for environmental sustainability and human health. In article number 2200865, Wenshuai Chen, Guihua Yu, and co-workers report the development of a nanostructured moisture-absorbing gel by integration of hygroscopic lithium salt and hydrophilic nanocellulose networks. The gel maintains a large hygroscopic active area for capturing water from air, and thus exhibits super-moisture-absorption ability. Even in a space with a volume over 20 000 times of its own, it demonstrates fast dehumidification without energy input and environment pollution.

A Nanostructured Moisture-Absorbing Gel for Fast and Large-Scale Passive Dehumidification.

Dehumidification is significant for environmental sustainability and human health. Traditional dehumidification methods involve significant energy consumption and have negative impact on the environment. The core challenge is to expose hygroscopic surfaces to the air, and appropriately store the captured water and avoid surface inactivation. Here, a nanostructured moisture-absorbing gel (N-MAG) for passive dehumidification, which consists of a hydrophilic nanocellulose network functionalized by hygroscopic lithium chloride, is reported. The interconnected nanocellulose can transfer the captured water to the internal space of the bulky N-MAG, eliminating water accumulation near the surfaces and hence enabling high-rate moisture absorption. The N-MAG can reduce the relative humidity from 96.7% to 28.7% in 6 h, even if the space is over 2 × 104 times of its own volume. The condensed water can be completely confined in the N-MAG, overcoming the problem of environmental pollution. This research brings a new perspective for sustainable humidity management without energy consumption and with positive environmental footprint.

Synergistic reinforcing and cross-linking effect of thiol-ene-modified cellulose nanofibrils on natural rubber

To achieve synergistic reinforcing and cross-linking effect across interface between hydrophilic nanocellulose and hydrophobic rubber, active thiol groups were introduced at reducing end of CNF while retaining hydroxyl groups on the surface, thus forming a percolation network in nanocomposites. The nanocomposites were obtained by casting/evaporating a mixture of dispersed modified CNF and NR in latex form, in which covalent cross-links were formed between thiol groups and double bonds of NR via photochemically initiated thiol-ene reaction. Strong interfacial interaction between NR matrix and end-modified CNF was characterized by Fourier-transform infrared spectroscopy. The structural and mechanical properties of the nanocomposites were evaluated by scanning electron microscopy, dynamic mechanical analysis and tensile tests. Compared to neat NR, the nanocomposite reinforced with 10 wt% modified CNF showed significantly higher values of tensile strength (0.33 to 5.83 MPa), Young's modulus (0.48 to 45.25 MPa) and toughness (2.63 to 22.24 MJ m−3).

Tensile and morphological properties of nanocrystalline cellulose and nanofibrillated cellulose reinforcedPLAbionanocomposites: A review

AbstractIn recent years, bionanocomposites have received growing attention in science and industry due to their renewability, biodegradability and superior mechanical properties. Nanocellulose is another promising material that use as a reinforcement filler for bionanocomposite materials due to its lightweight, high surface area, high mechanical strength, high aspect ratio and low density. Different nanocellulose loading, sources, surface modification/functionalization and properties of nanocellulose are important in the production of bionanocomposites. In general, nanocellulose reinforced PLA bionanocomposite offers enhancement in tensile strength and elastic modulus. However, only minimal nanocellulose loadings are required for optimal results due to the incompatibility between the hydrophilic nanocellulose and hydrophobic PLA. This paper reviews the sources of nanocellulose and the properties of nanocellulose with a focus on the tensile and morphological properties of PLA bionanocomposites. Applications of nanocellulose in various industries are discussed in this article. This review article provides some important information. First, this study reviewed the application of nanostructured cellulose in biodegradable polymers. There are two types of nanostructured cellulose: nanocrystalline cellulose (NCC) and nanofibrillated cellulose (NFC). Second, the status on articles published on nanocellulose and PLA/nanocellulose over the past 10 years is reported. Third, the authors of this paper implemented a holistic and critical review to provide a comprehensive understanding of the different properties between NCC and NFC, the application of nanocellulose in bionanocomposites, as well as the properties of PLA and PLA bionanocomposites. Moreover, the influence of NCC and NFC on the tensile and morphological properties of bionanocomposites is covered in this article.

Biofouling-resistant nanocellulose layer in hierarchical polymeric membranes: Synthesis, characterization and performance

In this study, we developed a hierarchical thin-film nanofibrous composite (TFNC) membrane with electrospun mat as substrate and hydrophilic nanocellulose as the antifouling barrier layer. We found that, due to the super-hydrophilic nature of the nanocellulose, the contact angle of the barrier layer (20−28°) decreased rapidly with time and reached nearly zero after a few seconds, whereby the membrane flux were remarkably higher (52L.m−2.h−1) than conventional polymeric membranes (4−14L.m−2.h−1) at a very low transmembrane pressure of 0.5 psi. In addition, the membrane surface was considerably more negatively-charged due to the high concentration of carboxylate groups, resulting in higher repulsive electrostatic forces between the barrier layer and the model foulant. As a result, the nanocellulose-based hierarchical membranes exhibited a lower fouling tendency (<10%) and a higher degree of protein rejection ratio compared with the conventional membranes (fouling tendency >30%). The effect of the nanocellulose layer thickness on the membrane fouling was also examined and it was demonstrated that the nanocellulose barrier layer thickness had a significant effect on the membrane fouling. The higher flux, lower fouling, and good rejection properties of this membrane system suggest nanocellulose is a promising barrier material for filtration membranes for water purification and other separation processes.

Crosslinked poly(vinyl acetate) (PVAc) reinforced with cellulose nanocrystals (CNC): Structure and mechanical properties

The structure of cellulose-based nanocomposites significantly influences their final mechanical properties. However, obtaining a good dispersion of hydrophilic nanocellulose materials in a hydrophobic polymer matrix is challenging. In this study, two unique methods were developed to improve the dispersion of cellulose nanocrystals (CNC) in a poly(vinyl acetate) (PVAc) matrix. One method was the crosslinking of PVAc by sodium tetraborate (borax), which is expected to prevent agglomeration of CNCs during the drying process, and the other method was the in-situ polymerization of vinyl acetate in the presence of CNCs to generate good compatibility between CNC and PVAc. The results showed that the crosslinking degree of PVAc could be varied by tuning the pH. The atomic force microscopy images illustrate that after drying, the in-situ polymerized PVAc/CNC composite was much better dispersed than the composite produced using mechanical mixing. The mechanical and thermo-mechanical characterizations indicate that the in-situ nanocomposite with 10 wt% of CNC had a higher strength and storage modulus compared with the mixed composite with the same CNC concentration. Further investigations of the restriction effect caused by the crosslinker are required.

Double emulsions for the compatibilization of hydrophilic nanocellulose with non-polar polymers and validation in the synthesis of composite fibers.

A route for the compatibilization of aqueous dispersions of cellulose nanofibrils (CNFs) with a non-polar polymer matrix is proposed to overcome a major challenge in CNF-based material synthesis. Non-ionic surfactants were used in CNF aqueous dispersions equilibrated with an organic phase (for demonstration, a polystyrene solution, PS, was used). Stable water-in-oil-in-water (W/O/W) double emulsions were produced as a result of the compromise between composition and formulation variables. Most remarkably, the proposed route for CNF integration with hydrophobic polymers removed the need for drying or solvent-exchange of the CNF aqueous dispersion prior to processing. The rheological behavior of the double emulsions showed strong shear thinning behavior and facilitated CNF-PS co-mixing in solid nanofibers upon electrospinning. The morphology and thermal properties of the resultant nanofibers revealed that CNFs were efficiently integrated in the hydrophobic matrix which was consistent with the high interfacial area of the precursor double emulsion. In addition, the morphology and quality of the composite nanofibers can be controlled by the conductivity (ionic strength) of the CNF dispersion. Overall, double emulsion systems are proposed as a novel, efficient and scalable platform for CNF co-processing with non-polar systems and they open up the possibility for the redispersion of CNFs after removal of the organic phase.

Dynamics of Hydration of Nanocellulose Films

The design of materials capable of mechanical responses to physical and chemical stimuli represents one of the most exciting and challenging areas of scientific research because of the huge number of their potential applications. This article is focused on the molecular events occurring in thin films of carboxylated nanocellulose fibers, which are capable of converting water gradients into mechanical movements at the macroscopic scale. The analysis of the mechano‐actuation, and of the conditions to obtain it, shows that the film movement is fast and reproducible, the gradient intensity is transduced into rate of displacement, and the response is observed at vapor pressures as low as 1.2 mm Hg. The actuation mechanism is associated to an efficient and reversible water sorption process by the hydrophilic nanocellulose fibers at the film interface. Conversely, water desorption is slow and follows a kinetic behavior supporting the presence of two binding sites for water molecules. The adsorbed water induces swelling of the surface nanocellulose layers and local structural rearrangement, however transitions between ordered and random coil conformations are not observed. The understanding of the actuation mechanisms of nanocellulose offers exciting opportunities to design macroscopic structures responding to chemical gradients by the assembly of simple molecular components.

In situ synthesis of bacterial cellulose/polycaprolactone blends for hot pressing nanocomposite films production

A series of bacterial cellulose (BC)/polycaprolactone (PCL) nanocomposite films were successfully prepared by supplementation of the BC culture medium with variable amounts of PCL powder followed by hot-pressing of the BC/PCL mixtures obtained after incubation. PCL powder was fully incorporated into the BC network during its production and did not change the BC network morphology. The obtained films showed a homogenous distribution of PCL throughout the BC network, as well as good thermal stability (up to 200°C) and improved mechanical properties, when compared to pristine PCL. In addition, the intrinsic biodegradability and biocompatibility of the nanocellulose fibers and PCL opens the possibility of using this novel nanocomposite in the biomedical field and food packaging. The BC biosynthetic approach combined with the hot-pressing proved successful for the sustainable development of nanocomposites combining hydrophobic thermoplastic matrices and hydrophilic nanocellulose fibers, without the use of harmful organic solvents commonly used to dissolve this type of polymeric matrices.

Use of Chemically Modified Nanocelluloses in Flotation of Hematite and Quartz

Nowadays, there are strong economical, ecological, and social incentives to develop novel green chemicals from renewable resources to reduce the environmental impact of processing. Cellulose, which is the most abundant natural polymeric source, offers one promising green alternative that could replace the present synthetic chemicals. In this study, two types of modified nanocelluloses (amphiphilic and hydrophilic) were produced and tested to understand their ability to function as collectors and depressants in the mineral flotation process for pure hematite and pure quartz. Hydrophilic nanocellulose (called dicarboxylic acid nanocellulose (DCC)) was observed to be a more selective depressant for hematite than for quartz. DCC seems to be most effective at a pH level of 6. Amphiphilic nanocrystalline celluloses (ANCCs) work as collectors. ANCCs were pH-dependent collectors, and they worked well at a pH value of 10 in the case of the investigated oxides (hematite and quartz). This research indicated that nanocelluloses functioned already at least at the same level as a commercial starch depressant for hematite and as an ether amine collector for quartz.

Increase in the water contact angle of composite film surfaces caused by the assembly of hydrophilic nanocellulose fibrils and nanoclay platelets.

Controlling the assembly modes of different crystalline nanoparticles in composites is important for the expression of specific characteristics of the assembled structures. We report a unique procedure for increasing water contact angles (CAs) of composite film surfaces via the assembly of two different hydrophilic components, nanocellulose fibrils and nanoclay platelets. The nanocellulose fibrils and nanoclay platelets used have ionic groups on their surfaces in high densities (∼1 mmol g(-1)) and have no hydrophobic surface. The increase in the CA of the nanocellulose/nanoclay composite films was thus analyzed on the basis of the air area fractions of their nanostructured surfaces following Cassie's law. The air area fractions were geographically estimated from the atomic force microscopy height profiles of the composite film surfaces. The CAs of the composite film surfaces were found to be well described by Cassie's law. Interestingly, the composite films consisting of two hydrophilic nanoelements with different shapes exhibited CAs larger than those of the individual neat films.

Polylactide latex/nanofibrillated cellulose bionanocomposites of high nanofibrillated cellulose content and nanopaper network structure prepared by a papermaking route

AbstractPrevious attempts to use polylactide (PLA) latex particles and nanofibrillated cellulose (NFC) in papermaking processing have been limited to low NFC content. In the present study, a bionanocomposite material was successfully produced using a PLA latex and NFC. The components were mixed using a wet mixing method and bionanocomposite films were made by filtration followed by hot pressing. In composite materials, the dispersion of the reinforcing component in the matrix is critical for the material properties. Biopolymers such as PLA are non‐polar and soluble only in organic solvents; NFC is, however, highly hydrophilic. By utilizing latex, i.e., an aqueous dispersion of biopolymer micro‐particles, wet mixing is possible and the problem of aggregation of the hydrophilic nanocellulose in organic solvent is avoided. The properties of the resulting NFC/PLA latex bionanocomposite films were analyzed. Thorough blending resulted in good dispersion of the reinforcing component within the matrix. Adding increasing amounts of NFC improved the Young's modulus, tensile strength, and strain at break of the bionanocomposite material. The increase in the tensile properties was linear with increasing NFC content as a result of the good dispersion. The NFC also improved the thermal stability of the bionanocomposite material. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012