Rod-like Cellulose Nanocrystals Research Articles

Nonlinear oscillatory rheology of aqueous suspensions of cellulose nanocrystals and nanofibrils

In this work, the nonlinear rheological behavior of aqueous suspensions composed of two typical nanocellulose [rod-like cellulose nanocrystals (CNCs) and filamentous cellulose nanofibrils (CNFs)] was examined and compared by using various large-amplitude oscillatory shear (LAOS) analysis methods, such as Fourier-transform rheology, stress decomposition, Chebyshev polynomials, and the sequence of physical processes. From our analysis, the nonlinear rheological parameters of higher harmonics, dissipation ratio, strain hardening ratio, shear thickening ratio, transient modulus, and cage modulus were obtained and quantitatively analyzed. CNCs tend to assemble to form anisotropic structures in an aqueous medium while the CNFs are entangled to form gels. The CNF suspensions demonstrated a significant viscous modulus overshoot and had stronger yield stresses, but the yield of CNC suspensions was more ductile. In the case of low concentrations, the CNF suspensions demonstrated stronger intracycle shear thickening behavior in medium-amplitude oscillatory shear region and lower dissipation ratios at small strain amplitudes. Although both nanocellulose suspensions revealed the existence of four intracycle rheological transition processes (viscoplastic deformation, structural recovery, early-stage yielding, and late-stage yielding), the CNF suspensions exhibited a stronger structural recovery ability. Larger strain amplitudes did not invariably result in a broader range of intracycle rheological transitions, which are also affected by the excitation frequency. The application of the various LAOS analysis methods provided valuable intracycle nonlinear rheological insights into nanocellulose suspensions, which are of great importance for enhancing their industrial perspectives.

Cellulose nanocrystals-strengthened, anti-drying, and anti-freezing hydrogels for human motion sensing and 3D printing

Recently, stretchable hydrogels have been widely applied in flexible wearable devices. However, their stability, sensitivity, and mechanical properties still remain significant shortcomings. In this work, a double-network and conductive hydrogel formed by sodium alginate and poly(vinyl alcohol) in a glycerol-water system is developed. The network consists of poly(vinyl alcohol) and sodium alginate with rod-like cellulose nanocrystals as a supporting structure, which provides enhanced mechanical properties such as high tensile strength (2.4 MPa), high toughness (4.61 MJ/m3), high compressive strength (7.83 MPa), as well as excellent fatigue resistance. On one hand, due to the incorporation of salt, the hydrogels are endowed with good electrical conductivity. On the other hand, since the hydrogels exhibit the ability to sense pressure and strain, it is considered to be a sensor that can be used to monitor various movements of human bodies. It is worth mentioning that the addition of glycerol provides the hydrogels good anti-freezing properties, and the hydrogels have an operating temperature tolerance as low as −25 °C, which allows the hydrogels to work well even in winter. In addition, the hydrogel solution has good injectability, gelling rate controllability, and biocompatibility, which makes it a good candidate in 3D printing. In summary, the hydrogel developed in this study has good application scenarios for applications such as electronic skin, flexible wearable devices, strain sensors, and 3D-printed scaffolds.

Cellulose Nanocrystals As a Key in Wearable Sensors

In recent years, the development of cellulose-based inks for 3D printing has received significant interest due to numerous cellulose and its derivatives properties [1], [2]. Carboxymethyl cellulose (CMC) is an anionic water-soluble cellulose derivative widely used as superabsorbent hydrogels [3]. Another cellulose derivative is cellulose nanocrystal (CNC), a rod-like nanoparticle that can be applied for the mechanical strengthening of hydrogels and also presents potential use in several applications in the biomedical field [2], [4]. Based on this, we have proposed to investigate if CMC and CNC mixtures result in cellulose-based nanocomposite gels suitable for extrusion printing of wearable sensors. Interactions between CNC and CMC resulted in physical gels, where rheological properties and extrusion printing parameters' effects were studied. A Modular Compact Rheometer (Anton Paar MCR-102, Austria) with a plate-plate geometry (50 mm diameter and 1 mm gap) at 25 °C was used to perform rheological measurements. Extrusion printing was performed on the customized 3DCloner Lab printer using a 22G nozzle tip of 25 mm in length and a diameter of 0.70 mm (Injex, Brazil). Gels presented shear-thinning, solid-like viscoelastic behavior, viscosity recovery, and continuous filaments obtained during printing. Moreover, the alignment of rod-like CNC during the printing process can be a key to improving properties. Tests with different print and extrusion speeds evidenced the influence of the wearable sensor's geometry and mechanical properties. Moreover, the low cytotoxicity of CMC/CNC crosslinked hydrogels was confirmed through an MTT assay of fibroblasts. Further testing is being conducted to evaluate the self-healing and conductive properties of the sensors by external stimuli. Moreover, low cytotoxicity to CMC/CNC crosslinked hydrogels was confirmed through an MTT assay of fibroblasts. External stimuli are being applied to evaluate the self-healing and conductive of the sensor printed.

.Cinnamaldehyde-enriched Pickering emulsions stabilized by modified cellulose I and II nanocrystals recycled from maple leaves for shrimp preservation

The utilization of biomass waste has attracted much interest, but such attention hasn't been paid to the abundant fallen maple leaves in Canada. Herein, we aim to obtain cellulose nanocrystals (CNCs) from maple leaves and explore their potential applications as sustainable stabilizers of Pickering emulsions for the preservation of food products with complicated structures. The results reveal that two types of CNCs were extracted from maple leaves at different alkaline conditions. Octenyl succinic anhydride was selected to modify rod-like CNCs, and the CNC-stabilized oil-in-water Pickering emulsions showed excellent stability. Cinnamaldehyde, a model antibacterial compound, was incorporated in the Pickering emulsions, which exhibited the improved storage stability and sustained antibacterial capacity towards both Gram-positive and Gram-negative bacteria. Shrimp was chosen as an example that has complicated surface structure and is hard to disinfect, and the CNC-stabilized Pickering emulsions could be easily sprayed on the surface of shrimp to inhibit the proliferation of bacteria and inactivate the psychrophilic bacteria responsible for shrimp spoilage at refrigerated condition, so as to preserve the quality of shrimp. Therefore, the current work suggests the possibility to utilize fallen maple leaves as a promising source of CNCs and the applications of CNC-stabilized Pickering emulsions in seafood preservation.

Using nanocellulose to improve heat-induced cull cow meat myofibrillar protein gels: effects of particle morphology and content.

Enhancing protein gel properties is essential to improve the texture of meat products. In this study, the improvement effects of three types of nanocellulose, i.e. rod-like cellulose nanocrystals (CNC), long-chain cellulose nanofibers (CNF) and spherical cellulose nanospheres (CNS) with different concentrations (1, 3, 5, 10, 15 and 20 g kg-1 ), on cull cow meat myofibrillar protein (MP) gel were investigated. Compared with needle-shaped CNC and spherical CNS, the addition of 10 and 20 g kg-1 long-chain CNF had the most significant improvement effect on gel hardness and water-holding capacity, respectively (P < 0.05), increasing to 160.1 g and 97.8%, respectively. In addition, the incorporation of long-chain CNF shortened the T2 relaxation time and induced the formation of the densest network structure and promoted the phase transition of the gel. However, excessive filling of nanocellulose would destroy the structure of the gel, which was not conducive to the improvement of gel properties. Fourier transform infrared results showed that there was no chemical reaction between the three nanocellulose types and MP, but the addition of nanocellulose was conducive to gel formation. The improvement of MP gel properties by adding nanocellulose mainly depends on its morphology and concentration. Nanocellulose with higher aspect ratio is more beneficial to the improvement of gel properties. For each nanocellulose type, there is an optimal addition amount for MP gel improvement. © 2023 Society of Chemical Industry.

Anisotropic Frictional Properties Induced by Cellulose Nanofibril Assembly.

The alignment of geometrically anisotropic nanomaterials regulates their functions. Self-ordering of rod-like cellulose nanocrystals (CNCs) results in liquid-crystal formation, and the ordering of the CNCs exhibits unique optical properties. Native cellulose nanofibrils (CNFs) are considered to be oriented, and thus the orientation is correlated with their functions, such as their mechanical strength and cell responses. In contrast, the ordering of artificially pulverized CNFs with high aspect ratios is restricted by their long fibrous shape. Here, we propose a facile fabrication method for non-uniaxial, fingerprint-like alignment of CNFs using the Langmuir-Blodgett technique. The obtained Langmuir-Blodgett films of CNFs exhibited anisotropic frictional properties depending on the orientation direction. This process for fabrication of CNF ultrathin films is expected to be used for novel surface design with desired structure-function correlations, which provides anisotropic surface properties to the material surface.

Characterization of semi-interpenetrating hydrogel based on Artemisia sphaerocephala Krasch Polysaccharide and cellulose nanocrystals crosslinked by ferric ions

Hydrogels are important bionic materials that can be used in a wide variety of biomedical applications. Artemisia sphaerocephala Krasch polysaccharide (ASKP) has been demonstrated to be crosslinked by ferric ions to form three-dimensional network. Here, a semi-interpenetrating network (semi-IPN) hydrogel based on ASKP and cellulose nanocrystals (CNC) crosslinked by ferric ions was fabricated and the effect of specific rod-like CNC was evaluated. It was found that the network of ASKP-Fe3+ hydrogel incorporated by CNC became denser along with the decreased pore diameter and the thickened pore wall. ASKP/CNC-Fe3+ hydrogel displayed an enhanced gel strength and water holding capacity. The dominant interaction of ASKP and CNC was hydrogen bonds proved by FTIR and QCM-D. Additionally, the elasticity of the semi-IPN hydrogel significantly increased along with the decrease of platform height in MSD curves based on particles tracking. These results may be caused by the fact that the rod-shaped CNC can be entangled with ASKP and prone to induce the orderly extension of ASKP chains, resulting in more hydroxyl and carboxyl groups exposed to be crosslinked with ferric ions. What's more, the stiff CNC located on the pore wall of ASKP-Fe3+ hydrogel can also strengthen the rigidity of network. Thus, this study suggests a new strategy to improve the properties of ASKP based hydrogel, and can be developed as a carrier to deliver iron ions.

Cellulose nanocrystals lime mortar based on biomimetic mineralization

Sticky rice-lime mortar has been widely used in the construction of traditional buildings. It has been known as the best available material for restoring ancient buildings. However, it is unbenevolent to use edible sticky rice for a large scale restoration considering hunger crises. In addition, the component of sticky rice is complex, the mechanism of how sticky rice mediates the properties of lime mortar is still unclear. In this work, as a kind of abundant, inedible and single-component polysaccharide, nematic cellulose nanocrystals (CNCs) were used to prepare lime mortars. The characteristics, such as compressive strength, molar percent of calcium carbonate, microscopic morphology, of lime mortars were characterized to explore the function of CNCs in lime mortars. Compressive strength is related to molar percent of calcium carbonate and the organization of CNCs. The main polymorph of calcium carbonate is calcite. Rod-like CNCs orient themselves in one direction and control calcium carbonate to grow along the particular direction of CNCs orientation based on biomimetic mineralization. External force field further organizes CNCs and the growth of calcium carbonate. It is promising to restore ancient building with lime mortar containing CNCs since the properties, such as compressive strength and polymorph of calcium carbonate, of lime mortar added CNCs are similar to that of traditional sticky rice-lime mortar. Additionally, the mechanism of biomimetic mineralization process of CNCs is clear. Our work opens a way to develop traditional material with new technology and new materials.

All-Aqueous Bicontinuous Structured Liquid Crystal Emulsion through Intraphase Trapping of Cellulose Nanoparticles.

Here, we describe the all-aqueous bicontinuous emulsions with cholesteric liquid crystal domains through hierarchical colloidal self-assembly of nanoparticles. This is achieved by homogenization of a rod-like cellulose nanocrystal (CNC) with two immiscible, phase separating polyethylene glycol (PEG) and dextran polymer solutions. The dispersed CNCs exhibit unequal affinity for the binary polymer mixtures that depends on the balance of osmotic and chemical potential between the two phases. Once at the critical concentration, CNC particles are constrained within one component of the polymer phases and self-assemble into a cholesteric organization. The obtained liquid crystal emulsion demonstrates a confined three-dimensional percolating bicontinuous network with cholesteric self-assembly of CNC within the PEG phase; meanwhile, the nanoparticles in the dextran phase remain isotropic instead. Our results provide an alternative way to arrest bicontinuous structures through intraphase trapping and assembling of nanoparticles, which is a viable and flexible route to extend for a wide range of colloidal systems.

Enhance Fracture Toughness and Fatigue Resistance of Hydrogels by Reversible Alignment of Nanofibers.

Biological tissues, such as heart valve, tendon, etc., possess excellent mechanical properties, which arises from their inherent anisotropic arrangement of soft and hard phases. Inspired by the anisotropic structures, many methods have been developed to synthesize hydrogels that can achieve mechanical properties comparable to biological tissues. Here, we describe a new method to enhance fracture toughness and fatigue resistance of hydrogels by introducing nanofibers which can reversibly align with elastic deformation to form an anisotropic structure. As a demonstration, we introduce stiff, rod-like cellulose nanocrystals (CNCs) into a polyacrylamide (PAAm) network. CNCs aggregate into clusters to form hard phases and entangle with the PAAm network. The CNC/PAAm composite hydrogel is initially isotropic, becomes anisotropic upon loading, and recovers to be isotropic upon unloading. During the deformation, the aligned CNC clusters at the crack tip can transmit the stress over the size of the cluster, effectively resisting crack growth. We use photoelasticity and small-angle X-ray scattering (SAXS) tests to observe the change of microstructures associated with deformation. The fracture toughness of CNC/PAAm hydrogels with different sizes of CNCs can reach 1000 J/m2. The fatigue threshold is about 100 J/m2, an order of magnitude higher than that of PAAm hydrogel. This work provides a simple and general method to strengthen hydrogels under both monotonic and cyclic loads.

Cellulose Nanocrystals-Incorporated Thermosensitive Hydrogel for Controlled Release, 3D Printing, and Breast Cancer Treatment Applications.

In situ-gel-forming thermoresponsive copolymers have been widely exploited in controlled delivery applications because their critical gel temperature is similar to human body temperature. However, there are limitations to controlling the delivery of biologics from a hydrogel network because of the poor networking and reinforcement between the copolymer networks. This study developed an in situ-forming robust injectable and 3D printable hydrogel network based on cellulose nanocrystals (CNCs) incorporated amphiphilic copolymers, poly(ε-caprolactone-co-lactide)-b-poly(ethylene glycol)-b-poly(ε-caprolactone-co-lactide (PCLA). In addition, the physicochemical and mechanical properties of injectable hydrogels were controlled by physically incorporating CNCs with amphiphilic PCLA copolymers. CNCs played an unprecedented role in physically reinforcing the PCLA copolymers' micelle network via intermicellar bridges. Apart from that, the free-flowing closely packed rod-like CNCs incorporated PCLA micelle networks at low temperature transformed to a stable viscoelastic hydrogel network at physiological temperature. CNC incorporated PCLA copolymer sols effectively coordinated with hydrophobic doxorubicin and water-soluble lysozyme by a combination of hydrophobic and hydrogen bonding interaction and controlled the release of biologics. As shown by the 3D printing results, the biocompatible PCLA hydrogels continuously extruded during printing had good injectability and maintained high shape fidelity after printing without any secondary cross-linking steps. The interlayer bonding between the printed layers was high and formed stable 3D structures up to 10 layers. Subcutaneous injection of free-flowing CNC incorporated PCLA copolymer sols to BALB/c mice formed a hydrogel instantly and showed controlled biodegradation of the hydrogel depot without induction of toxicity at the implantation sites or surrounding tissues. At the same time, the in vivo antitumor effect on the MDA-MB-231 tumor xenograft model demonstrated that DOX-loaded hydrogel formulation significantly inhibited the tumor growth. In summary, the CNC incorporated biodegradable hydrogels developed in this study exhibit a prolonged release with special release kinetics for hydrophobic and hydrophilic biologics.

Improved piezoelectricity of porous cellulose material via flexible polarization-initiate bridge for self-powered sensor

Self-powered piezoelectric sensors based on cellulose nanocrystal (CNC) porous materials are light-weight and portable, whereas using unmodified CNCs can hardly obtain enough piezoelectric properties without external strong polarization due to its irreversible deformation caused by low toughness. Here, we bonded rod-like CNCs with a soft polymer, poly ethylene glycol (PEG), and hypothesized that PEG could toughen the material and its dielectric signal could induce the CNC polarization. We further adsorbed graphene (GR) as surface electrodes to prepare a CNC-PEG-GR piezoelectric porous material with density of 0.096 g·cm−3. The voltage output reached maximum when the frequency matched the dielectric relaxation frequency of PEG. We also increased the length-diameter ratio of porous material pores from 1.1 to 3.3 by adjusting its freeze-drying process, and the voltage output could reach to 0.7 V at a moderate ratio. They could be conveniently integrated into portable self-powered sensors applied to the intelligent wearable electronic devices.

Embedding Mn2+ in polymer coating on rod-like cellulose nanocrystal to integrate MRI and photothermal function

Grafting Mn ions on 1D particles can produce high-performance MRI agents. However, the motion of Mn ions may cause Mn aggregation and then attenuate imaging contrast. Here, we proposed an MRI-promotion strategy based on embedding Mn2+ into crosslinked polydopamine (PDA) coating on rod-like cellulose nanocrystals. The results indicate that the slow relaxation of PDA molecular chains restricts the motion of embedded Mn2+. When the embedded Mn2+ content raises up to 2.25 wt%, the particles display a longitudinal relaxivity of 38.08 mM−1·s−1. Such a relaxivity is over 6.6 times of the sample with adsorbed 0.65 wt% Mn2+. The aspect ratio of nanoparticles even increases from 14.2 to 20.7 as embedding Mn2+ concentration increases. Then, the photothermal conversion efficiency of nanoparticles increases from 17.7 % to 44.4 %. This high photothermal conversion efficiency contributes this kind of MRI agent with embedded Mn2+ to the application potential of integrating tumor diagnosis and treatment.

Isolation and Properties of Cellulose Nanocrystals Fabricated by Ammonium Persulfate Oxidation from Sansevieria trifasciata Fibers

Cellulose nanocrystals (CNCs) were successfully prepared from Sansevieria trifasciata fibers (STFs) via ammonium persulfate (APS) oxidation in this study. The influences of the APS concentration (1.1, 1.5, and 1.9 M) and oxidation temperature (60, 70, and 80 °C) on the characteristics of CNCs were studied. The resulting CNCs were characterized using Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), transmission electron microscopy (TEM), and thermogravimetric analysis (TGA). The TEM observations revealed that the rod-like CNCs possessed average length and diameter ranges of 96 to 211 nm and 5 to 13 nm, respectively, which led to an aspect ratio range of 16–19. The optimum conditions for maximum crystallinity were achieved at an oxidation temperature of 70 °C, a reaction time of 16 h, and an APS concentration of 1.5 M. All CNCs exhibited lower thermal stability compared to the STFs. The CNCs could be produced from the STFs through the APS oxidation process and showed potential as nanocomposite reinforcement materials.

Impact of the Incorporation of Nano-Sized Cellulose Formate on the End Quality of Polylactic Acid Composite Film.

Polylactic acid (PLA) films with good sustainable and biodegradable properties have been increasingly explored recently, while the poor mechanical property of PLA limits its further application. Herein, three kinds of nano-sized cellulose formate (NCF: cellulose nanofibril (CNF), cellulose nanocrystal (CNC), and regenerated cellulose formate (CF)) with different properties were fabricated via a one-step formic acid (FA) hydrolysis of tobacco stalk, and the influence of the properties of NCF with different morphologies, crystallinity index (CrI), and degree of substitution (DS) on the end quality of PLA composite film was systematically compared. Results showed that the PLA/CNC film showed the highest increase (106%) of tensile strength compared to the CNF- and CF-based films, which was induced by the rod-like CNC with higher CrI. PLA/CF film showed the largest increase (50%) of elongation at the break and more even surface, which was due to the stronger interfacial interaction between PLA and the CF with higher DS. Moreover, the degradation property of PLA/CNF film was better than that of other composite films. This fundamental study was very beneficial for the development of high-quality, sustainable packaging as an alternative to petroleum-based products.

Effect of Graft Molecular Weight and Density on the Mechanical Properties of Polystyrene-Grafted Cellulose Nanocrystal Films

Polymer-grafted nanoparticle (PGN) films were prepared from polystyrene (PS) grafted to rodlike cellulose nanocrystals (MxG-CNC-g-PS) with a controllable grafting density (0.03–0.25 chains/nm2) and...

Distinct liquid crystal self-assembly behavior of cellulose nanocrystals functionalized with ionic liquids

Rod-like cellulose nanocrystals (CNCs) show the intriguing liquid crystal self-assembly ability. The understanding of the self-assembly behavior of CNCs is of fundamental importance for constructing cellulose-based functional materials. The presented work explores how the liquid crystal self-assembly behavior of CNCs is affected by the grafted ionic liquids (IL) [VBIm][BF4]. The results demonstrate that the IL modified CNC (CNC-IL) with positive charged form chiral nematic structure in suspensions, which was normally observed in negative charged ones. Significantly, such liquid-crystalline organization can be obtained under much lower concentration (as low as 1.0 wt%) than that of the non-functionalized CNCs prepared from paper pulp (~ 3.0 wt%). Moreover, for CNC-IL concentrations varying from 1.0 to 4.0 wt%, the tactoids (showing obvious fingerprint texture) coexist with the disordered CNC phase, rather than separating into two phases. Unlike original CNCs, the pitch of chiral nematic tactoids increases with increasing concentration of CNC-IL. Our study suggests that the distinct liquid crystal self-assembly behavior of CNC-IL is related to the restricted mobility of CNCs rods due to the increase in CNCs particle size and the high viscosity of CNC-IL suspension as the result of IL surface modification. The study of the liquid crystal assembly behavior of IL modified CNCs provides some new insight to understand the intriguing chiral nematic self-assembly of CNCs and for construction of CNC-IL reinforced nanocomposites.

Hydrophobically modified pullulan adsorption onto rod-like cellulose nanocrystals

Hydrophobically modified pullulan adsorption onto rod-like cellulose nanocrystals

Multi-axis alignment of Rod-like cellulose nanocrystals in drying droplets

HypothesisRadial capillary flow in evaporating droplets carry suspended nanoparticles to its periphery where they are deposited and form a coffee-ring. Rod-like nanoparticles seeking to minimize their capillary energy will align with their long-axis parallel to the contact line. Particles exhibiting electrostatic repulsion, such as cellulose nanocrystals (CNCs), establish a competition between capillary flow-induced impingement against a growing coffee-ring and entropic minimization leading to enhanced particle mobility. Therefore, balancing these effects by manipulating the local particle concentration in drying droplets should result in deposition with a controlled orientation of CNCs. ExperimentsThe dynamic local order in aqueous suspensions of CNCs in evaporating sessile droplets was investigated through time-resolved polarized light microscopy. The spatial distribution of alignment in deposited CNCs was explored as a function of nanoparticle concentration, droplet volume, initial degree of anisotropy, and substrate hydrophobicity. Computational analysis of the rotational Péclet number during evaporation was also investigated to evaluate any effects of shear-induced alignment. FindingsMultiple modes of orientation were identified suggesting local control over CNC orientation and subsequent properties can be attained via droplet-based patterning methods. Specifically, high local particle concentrations led to tangential alignment and lower local particle concentrations resulted in new evidence for radial alignment near the center of dried droplets.

Hemocompatibility, biodegradability and acute toxicity of acetylated cellulose nanocrystals of different types in comparison

Promotion of promising cellulose nanocrystals (CNC) is largely dependent on the relationship between their morphology, surface chemical composition, and supramolecular structure with toxicity, hemocompatibility, and biodegradability. This paper outlines comparative and integrated analysis of the mentioned biocompatibility aspects of partially acetylated rod-, and disc-lake morphology of CNC with crystalline cellulose allomorphs I and II. These data have also included the study of CNC obtained from the sulfuric acid solutions. The aqueous solution of all types of tested CNC has not been toxic to mice after oral administration. Morphology of internal organs has not changed. However, in case of disc-like particles, the kidney mass coefficient noticeably changed. CNC have neither triggered platelet aggregation nor destroyed the red cell membrane. Intravenous administration to rabbits has not affected the plasma clotting time. Rod-like CNC are more resistant, and the disc-like particles are more susceptible to degradation under the influence of cellulases.