Rod-like Cellulose Nanocrystals Research Articles

A Self-Healing Cellulose Nanocrystal-Poly(ethylene glycol) Nanocomposite Hydrogel via Diels–Alder Click Reaction

Self-healing hydrogels are particularly desirable for increased safety and functional lifetimes because of stress-induced deformation and propagation of cracks. In this paper, we report a tough, highly resilient, fast self-recoverable, and self-healing nanocomposite hydrogel, which builds an interpenetrated network encapsulating rod-like cellulose nanocrystals (CNCs) by flexible polymer chains of poly(ethylene glycol) (PEG). A thermally reversible covalent Diels–Alder click reaction between furyl-modified CNCs and maleimide-end-functionalized PEG was confirmed by Fourier transform infrared spectroscopy. Uniaxial tensile tests and unconfined compression tests displayed outstanding mechanical properties of the hydrogels with a high fracture elongation up to 690% and a fracture strength up to 0.3 MPa at a strain of 90%. Cyclic loading–unloading tests showed excellent self-recovery and antifatigue properties of the nanocomposite hydrogels. The self-healing capability of nanocomposite hydrogels assessed by ten...

Strong and Stiff: High-Performance Cellulose Nanocrystal/Poly(vinyl alcohol) Composite Fibers.

The mechanical properties of rodlike cellulose nanocrystals (CNCs) suggest great potential as bioderived reinforcement in (nano)composites. Poly(vinyl alcohol) (PVOH) is a useful industrial material and very compatible with CNC chemistry. High performance CNC/PVOH composite fibers were produced coaxial coagulation spinning, followed by hot-drawing. We showed that CNCs increase the alignment and crystallinity of PVOH, as well as providing direct reinforcement, leading to enhanced fiber strength and stiffness. At 40 wt % CNC loading, the strength and stiffness reached 880 MPa and 29.9 GPa, exceeding the properties of most other nanocellulose based composite fibers previously reported.

Rod-Like Nanoparticles with Striped and Helical Topography.

The behavior of nanoparticles in solution is largely dominated by their shape and interaction potential. Despite considerable progress in the preparation of patchy and compartmentalized particles, access to nanoparticles with complex surface patterns and topographies remains limited. Here, we show that polyanionic brushes tethered to rod-like cellulose nanocrystals (CNCs) spontaneously develop a striped or helical topography through interpolyelectrolyte complexation with polycationic diblock copolymers. Using cryogenic transmission electron microscopy (cryo-TEM) and tomography (cryo-ET), we follow the complexation process and analyze the delicate 3D topography on the CNC surface. The described approach is facile and modular and can be extended to other block chemistries, nanoparticles, and surfaces, thereby providing a versatile platform toward surface-patterned particles with complex topographies and spatially arranged functional groups.

Morphological influence of cellulose nanoparticles (CNs) from cottonseed hulls on rheological properties of polyvinyl alcohol/CN suspensions

The present work describes the isolation of cellulose nanoparticles (CNs) with different morphologies and their influence on rheological properties of CN and CN-poly (vinyl alcohol) (PVA) suspensions. Cottonseed hulls were used for the first time to extract three types of CNs, including fibrous cellulose nanofibers, rod-like cellulose nanocrystals and spherical cellulose nanoparticles through mechanical and chemical methods. Rheology results showed that the rheological behavior of the CN suspensions was strongly dependent on CN concentration and particle morphology. For PVA/CN systems, concentration of PVA/CN suspension, morphology of CNs, and weight ratio of CN to PVA were three main factors that influenced their rheology behaviors. This research reveals the importance of CN morphology and composition concentration on the rheological properties of PVA/CN, providing new insight in preparing high performance hydrogels, fibers and films base on PVA/CN suspension systems.

Physicochemical and Mechanical Properties of Gelatin Reinforced with Nanocellulose and Montmorillonite

Organic rodlike cellulose nanocrystals extracted from sisal fibers and inorganic montmorillonite based on silicate layers were employed to develop bionanocomposites based on gelatin matrix. Bionanocomposites with cellulose na... | Find, read and cite all the research you need on Tech Science Press

New Approach for Single-Step Extraction of Carboxylated Cellulose Nanocrystals for Their Use As Adsorbents and Flocculants

A simple approach was developed to isolate cellulose nanocrystals (CNCs) with carboxylic groups from microcrystalline cellulose (MCC). The effect of reaction time on the morphology, microstructure, and thermal stability of isolated CNCs was investigated. The rod-like CNCs with size of 200–250 nm in length and about 15–20 nm in width were obtained by one-step citric/hydrochloric acid (C6H8O7/HCl) hydrolysis of MCC. The CNCs extracted at 4 h showed the highest carboxylic group content which led to a high absolute zeta potential value up to 46.63 mV. Moreover, these CNCs may be used as cationic dye adsorbent (methylene blue) and efficient flocculants with excellent coagulation–flocculation capability to kaolin suspension with a turbidity removal of 99.5%.

A universal route for the simultaneous extraction and functionalization of cellulose nanocrystals from industrial and agricultural celluloses

A simple route was designed to extract the cellulose nanocrystals (CNCs) with formate groups from industrial and agricultural celluloses like microcrystalline cellulose (MCC), viscose fiber, ginger fiber, and bamboo fiber. The effect of reaction time on the microstructure and properties of the CNCs was investigated in detail, while microstructure and properties of different CNCs were compared. The rod-like CNCs (MCC) with hundreds of nanometers in length and about 10 nm in width, nanofibrillated CNCs (ginger fiber bamboo fiber) with average width of 30 nm and the length of 1 μm, and spherical CNCs (viscose fiber) with the width of 56 nm were obtained by one-step HCOOH/HCl hydrolysis. The CNCs with improved thermal stability showed the maximum degradation temperature (T max) of 368.9–388.2 °C due to the introduction of formate groups (reducibility) and the increased crystallinity. Such CNCs may be used as an effective template for the synthesis of nanohybrids or reinforcing material for high-performance nanocomposites.

Enhanced Mechanical Properties in Cellulose Nanocrystal-Poly(oligoethylene glycol methacrylate) Injectable Nanocomposite Hydrogels through Control of Physical and Chemical Cross-Linking.

While injectable hydrogels have several advantages in the context of biomedical use, their generally weak mechanical properties often limit their applications. Herein, we describe in situ-gelling nanocomposite hydrogels based on poly(oligoethylene glycol methacrylate) (POEGMA) and rigid rod-like cellulose nanocrystals (CNCs) that can overcome this challenge. By physically incorporating CNCs into hydrazone cross-linked POEGMA hydrogels, macroscopic properties including gelation rate, swelling kinetics, mechanical properties, and hydrogel stability can be readily tailored. Strong adsorption of aldehyde- and hydrazide-modified POEGMA precursor polymers onto the surface of CNCs promotes uniform dispersion of CNCs within the hydrogel, imparts physical cross-links throughout the network, and significantly improves mechanical strength overall, as demonstrated by quartz crystal microbalance gravimetry and rheometry. When POEGMA hydrogels containing mixtures of long and short ethylene oxide side chain precursor polymers were prepared, transmission electron microscopy reveals that phase segregation occurs with CNCs hypothesized to preferentially locate within the stronger adsorbing short side chain polymer domains. Incorporating as little as 5 wt % CNCs results in dramatic enhancements in mechanical properties (up to 35-fold increases in storage modulus) coupled with faster gelation rates, decreased swelling ratios, and increased stability versus hydrolysis. Furthermore, cell viability can be maintained within 3D culture using these hydrogels independent of the CNC content. These properties collectively make POEGMA-CNC nanocomposite hydrogels of potential interest for various biomedical applications including tissue engineering scaffolds for stiffer tissues or platforms for cell growth.

Spherical and rod-like dialdehyde cellulose nanocrystals by sodium periodate oxidation: Optimization with double response surface model and templates for silver nanoparticles

A novel double response surface model is used first time to optimize a regioselective process to prepare spherical di- aldehyde cellulose nanocrystals (SDACN) and rod-like dialdehyde cellulose nanocrystals (RDACN) via one-step sodium pe- riodate (NaIO4) oxidation. The influence of four preparation factors (solid-liquid ratio, NaIO4 concentration, reaction time and temperature) on the yields and aldehyde contents of the final products were evaluated. For comparison, rod-like cellulose nanocrystals (CN-M and CN-S) were prepared by hydrochloric/formic acid hydrolysis and sulfuric acid hydrolysis, respectively. The RDACN shows high crystallinity of 82%, while SDACN presents low crystallinity due to the high degree of oxidation. Thus, SDACN has poorer thermal stability than RDACN and CN-M, but higher than CN-S. Compared to CN-M, SDACN with higher aldehyde contents as templates is beneficial to deposit more Ag nanoparticles with diameters of 30±4 nm and the resultant nanohybrids exhibit good antibacterial activities against both Gram-negative E. coli and Gram-positive S. aureus.

Negative Diamagnetic Anisotropy and Birefringence of Cellulose Nanocrystals

We report magnetic birefringence measurements up to high fields (17.5 T) of dilute aqueous suspensions of rod-like cellulose nanocrystals with well characterized distributions of lengths, widths and thicknesses. We compare these data with three models, one with colinear (1), one with perpendicular cylindrically symmetric tensors for diamagnetic susceptibility and refractive index (2) and one with biaxial diamagnetic anisotropy (3). We find that taking into account polydispersities of length, width, and thickness is essential for accurate fitting and that model 1 is the most appropriate, presumably because of the twisting of the suspended nanocrystal along their long axis. The best-fitted susceptibility anisotropy was Δχz(xy) = χzz–(χxx+χyy)/2 = −2.44 × 10–6 when considering only the crystalline core of nanocrystals and, more appropriately, Δχz(xy) = −0.95 × 10–6 when including crystalline core and skin. The latter value is slightly higher than Δχz(xy) = −0.68(5) × 10–6 deduced from estimations using Pasca...

Free-Standing Optically Switchable Chiral Plasmonic Photonic Crystal Based on Self-Assembled Cellulose Nanorods and Gold Nanoparticles.

Photonic crystals incorporating with plasmonic nanoparticles have recently attracted considerable attention due to their novel optical properties and potential applications in future subwavelength optics, biosensing and data storage device. Here we demonstrate a free-standing chiral plasmonic film composed of entropy-driven self-co-assembly of gold nanoparticles (GNPs) and rod-like cellulose nanocrystals (CNCs). The CNCs-GNPs composite films not only preserve the photonic ordering of the CNCs matrix but also retain the plasmonic resonance of GNPs, leading to a distinct plasmon-induced chiroptical activity and a strong resonant plasmonic-photonic coupling that is confirmed by the stationary and ultrafast transient optical response. Switchable optical activity can be obtained by either varying the incidence angle of lights, or by taking advantage of the responsive feature of the CNCs matrix. Notably, an angle-dependent plasmon resonance in chiral nematic hybrid film has been observed for the first time, which differs drastically from that of the GNPs embed in three-dimensional photonic crystals, revealing a close relation with the structure of the host matrix. The current approach for fabricating device-scale, macroscopic chiral plasmonic materials from abundant CNCs with robust chiral nematic matrix may enable the mass production of functional optical metamaterials.

Redox-responsive polycation-functionalized cotton cellulose nanocrystals for effective cancer treatment.

Carbon nanotubes have excellent penetrability and encapsulation efficiency in the fields of drug and gene delivery. Because of their excellent physicochemical properties, biocompatible rodlike cellulose nanocrystals (CNCs) were reportedly expected to replace carbon nanotubes. In this work, CNCs from natural cotton wool were functionalized with disulfide bond-linked poly(2-(dimethylamino)ethyl methacrylate) (PDMAEMA) brushes for effective biomedical applications. A range of CNC-graft-PDMAEMA vectors (termed as CNC-SS-PDs) with various molecular weights of PDMAEMA were synthesized. Under reducible conditions, PDMAEMA chains can be easily cleaved from CNCs. The gene condensation ability, reduction sensitivity, cytotoxicity, gene transfection, and in vivo antitumor activities of CNC-SS-PDs were investigated in detail. The CNC-SS-PDs exhibited good transfection efficiencies and low cytotoxicities. The needlelike shape of CNCs had an important effect on enhancing transfection efficiency. The antitumor effect of CNC-SS-PDs was evaluated by a suicide gene/prodrug system (cytosine deaminase/5-fluorocytosine, CD/5-FC) in vitro and in vivo. This research demonstrates that the functionalization of CNCs with redox-responsive polycations is an effective method for developing novel gene delivery systems.

Droplets of cellulose nanocrystal suspensions on drying give iridescent 3-D “coffee-stain” rings

Films prepared from aqueous suspensions of cellulose nanocrystals (CNC) often display iridescent colors due to the reflection of light from the helicoidal orientation of the rod-like CNC in the film. Droplets of CNC suspension deposited on a plane surface evaporate to give films that display iridescent rings. Profilometry measurements across the rings show that the outer edge of the films is much thicker than the region in the center. This is ascribed to a “coffee-stain” effect; the CNC are transported to the outer edge for droplets where the contact line is pinned during evaporation. The gradient in concentration across the ring results in a color gradient, with the longer wavelengths decreasing towards the center of the sample, in accord with the hypothesis of a two-stage process for CNC chiral nematic color formation.

2-Hydroxypropyltrimethylammonium xylan adsorption onto rod-like cellulose nanocrystal

Chemical incompatibility and relatively weak interaction between lignocellulosic fibers and synthetic polymers have made studies of wood fiber-thermoplastic composite more challenging. In this study, adsorption of 2-hydroxypropyltrimethylammonium xylans onto rod-like cellulose nanocrystals are investigated by zeta-potential measurements, and polarized and depolarized dynamic light scattering as a factor for better understanding of lignocellulosic fibers and cellulose nanocrystals. Zeta-potential measurements show xylan derivative adsorption onto cellulose nanocrystals. Decay time distributions of the ternary system and binary system from dynamic light scattering show that aggregates exist in the binary system and they disappear in the ternary system. At low 2-hydroxypropyltrimethylammonium xylan concentrations relative to that of cellulose nanocrystal, xylan derivatives adsorbed onto some of the cellulose nanocrystal. Hence, more xylan derivatives adsorbed onto cellulose nanocrystal increased with increasing xylan derivative concentration. Also, the concentration dependence of the ratio of the rotational diffusion coefficient to the translational diffusion coefficient revealed a strong adsorptive interaction between xylan derivatives and the cellulose nanocrystals.

Bioplastic based on starch and cellulose nanocrystals from rice straw

Bioplastic based on starch as the matrix and cellulose nanocrystals from rice straw as reinforcing filler were prepared in this study. The isolation of cellulose nanocrystal (CNC) followed a series of steps: delignification, sulfuric acid hydrolysis, and sonication. The process afforded short, rod-like CNCs with particle diameter ranging from 10 to 12 nm and crystallinity index of 76.1%. Fourier transform infrared analysis of the CNCs also confirmed absorption patterns typical of cellulose and the removal of silica. Bioplastic with different starch-to-CNC ratios were prepared by solution casting and evaporation method. Scanning electron micrographs of the films showed uniform dispersion of CNC in the starch matrix. Mechanical tests revealed that both tensile strength and modulus significantly increased with increasing CNC load while percent elongation decreased. The moisture uptake of the films reinforced with CNC also decreased an indication of improvement in water resistance. However, the thermal stability of the films decreased by the addition of CNC.

Novel approach to extract thermally stable cellulose nanospheres with high yield

A facile approach for extracting cellulose nanospheres (SCNCs) was presented through hydrochloric acid hydrolysis of lyocell fibers under hydrothermal condition. The SCNCs showed spherical nanoparticles with an average diameter of 25nm. Compared to the lyocell fibers, high yield of up to 85.3%, crystallinity of 85.2% and the maximum degradation temperature (Tmax) of 347.2°C for the SCNCs were achieved. Moreover, the morphology, microstructure, and thermal stability of SCNCs and rod-like cellulose nanocrystals (RCNCs) were compared. It was found that the SCNCs was less thermally stable than RCNCs, whereas the better suspension stability of SCNCs was observed due to the particular nanospherical structure and the existence of ammonium groups on the SCNCs, and these ammonium groups could easily be removed through heat treatment.

Water-Responsive Mechanically Adaptive Nanocomposites Based on Styrene–Butadiene Rubber and Cellulose Nanocrystals—Processing Matters

Biomimetic, stimuli-responsive polymer nanocomposites based on a hydrophobic styrene-butadiene rubber (SBR) matrix and rigid, rod-like cellulose nanocrystals (CNCs) isolated from cotton were prepared by three different approaches, and their properties were studied and related to the composition, processing history, and exposure to water as a stimulus. The first processing approach involved mixing an aqueous SBR latex with aqueous CNC dispersions, and films were subsequently formed by solution-casting. The second method utilized the first protocol, but films were additionally compression-molded. The third method involved the formation of a CNC organogel via a solvent exchange with acetone, followed by infusing this gel, in which the CNCs form a percolating network with solutions of SBR in tetrahydrofuran. The thermomechanical properties of the materials were established by dynamic mechanical thermal analysis (DMTA). In the dry state, all nanocomposites show much higher tensile storage moduli, E', than the neat SBR or the SBR latex. E' increases with the CNC content and depends strongly on the processing method, which appears to influence the morphology of the SBR nanocomposites produced. The highest E' values were observed for the solution cast samples involving an SBR latex, where E' increased from 3 MPa for the neat SBR to ca. 740 MPa for the nanocomposite containing 20% v/v CNCs. Upon submersion in deionized water, a dramatic reduction of E' was observed, for example from 740 to 5 MPa for the solution-cast nanocomposite containing 20% v/v CNCs. This change is interpreted as a disengagement of the percolating CNC network, on account of modest aqueous swelling and competitive hydrogen bonding of water molecules with the CNCs. It is shown that the method of preparation also influenced the swelling behavior and kinetics of modulus switching, consistent with different arrangements of the CNCs, which serve as channels for water absorption and transport within the hydrophobic SBR matrix.

Simple approach to reinforce hydrogels with cellulose nanocrystals.

The physical crosslinking of colloidal nanoparticles via dynamic and directional non-covalent interactions has led to significant advances in composite hydrogels. In this paper, we report a simple approach to fabricate tough, stretchable and hysteretic isotropic nanocomposite hydrogels, where rod-like cellulose nanocrystals (CNCs) are encapsulated by flexible polymer chains of poly(N,N-dimethylacrylamide) (PDMA). The CNC-PDMA colloidal clusters build a homogeneously cross-linked network and lead to significant reinforcing effect of the composites. Hierarchically structured CNC-PDMA clusters, from isolated particles to an interpenetrated network, are observed by transmission electron microscopy measurements. Dynamic shear oscillation measurements are applied to demystify the differences in network rheological behaviors, which were compared with network behaviors of chemically cross-linked PDMA counterparts. Tensile tests indicate that the hybrid hydrogels possess higher mechanical properties and a more efficient energy dissipation mechanism. In particular, with only 0.8 wt% of CNC loading, a 4.8-fold increase in Young's modulus, 9.2-fold increase in tensile strength, and 5.8-fold increase in fracture strain are achieved, which is ascribed to a combination of CNC reinforcement in the soft matrix and CNC-PDMA colloidal cluster conformational rearrangement under stretching. Physical interactions within networks serve as reversible sacrificial bonds that dissociate upon deformation, exhibiting large hysteresis as an energy dissipation mechanism via cluster mobility. This result contrasts with the case of chemically cross-linked PDMA counterparts where the stress relaxation is slow due to the permanent cross-links and low resistance against crack propagation within the covalent network.

Analysis of cellulose nanocrystal rod lengths by dynamic light scattering and electron microscopy

A method to characterize the length (L) of rod-like cellulose nanocrystal (CNC) particles is described. It is based on dynamic light scattering (DLS) and electron microscopy. Measurement of translational diffusion coefficient from DLS along with diameter measurements from electron microscopy is used in Broersma translational diffusion coefficient equation to calculate the CNC particle L. For wood based CNC rods, diameter of 15 nm measured by scanning electron microscopy (SEM) and translational diffusion coefficient of 5.21 × 10−12 m2/s measured by DLS give particle L of 271 nm from Broersma’s relation. This one and other calculated L values for various rod-like particles are in good agreement with the L of the particles measured either by transmission or SEM.

Injectable Polysaccharide Hydrogels Reinforced with Cellulose Nanocrystals: Morphology, Rheology, Degradation, and Cytotoxicity

Injectable hydrogels based on carboxymethyl cellulose and dextran, reinforced with rigid rod-like cellulose nanocrystals (CNCs) and aldehyde-functionalized CNCs (CHO-CNCs), were prepared and characterized. The mechanical properties, internal morphology, and swelling of injectable hydrogels with unmodified and modified CNCs at various loadings were examined. In all cases, gelation occurred within seconds as the hydrogel components were extruded from a double-barrel syringe, and the CNCs were evenly distributed throughout the composite, as observed by scanning and transmission electron microscopy. When immersed in purified water or 10 mM PBS, all CNC-reinforced hydrogels maintained their original shape for more than 60 days. The maximum storage modulus was observed in hydrogels with 0.250 wt % of unmodified CNCs and 0.375 wt % of CHO-CNCs. CHO-CNCs acted as both a filler and a chemical cross-linker, making the CHO-CNC-reinforced hydrogels more elastic, more dimensionally stable, and capable of facilitating higher nanoparticle loadings compared to hydrogels with unmodified CNCs, without sacrificing mechanical strength. No significant cytotoxicity to NIH 3T3 fibroblast cells was observed for the hydrogels or their individual components. These properties make CNC-reinforced injectable hydrogels of potential interest for various biomedical applications such as drug delivery vehicles or tissue engineering matrices.