Rod-shaped Cellulose Nanocrystals Research Articles

On rheological properties of disc-shaped cellulose nanocrystals

The rheological properties of a substance depend greatly on its morphology, and rod-shaped cellulose nanocrystals (RCNCs) and cellulose nanofibrils (CNFs) have been extensively studied for their rheological properties. Nevertheless, the rheological properties of disc-shaped cellulose nanocrystals (DCNCs) with crystalline allomorph II derived from mercerized cellulose remain unknown yet. This work investigated the DCNCs' rheological properties in depth using steady-shear and oscillation measurements. At the same concentration, DCNC's suspension viscosity is lower than that of RCNC; RCNC has an instinct viscosity of 258.2, while DCNC has 187.9. Comparing RCNC suspensions with cellulose nanorods, DCNC has a lower aspect ratio and exhibits a distinct steady shear behavior. Under polarized film, DCNC suspension cannot self-assemble into chiral or liquid crystal phases, and with increasing concentrations, the system transitions from an isotropic phase to a gel phase. Oscillation sweeps demonstrate that the gel transition occurs at 7 %–8 %. Based on thixotropic recovery sweep outcomes, the high-stress oscillations enhance the network structure of DCNC suspensions, which is significantly different from that of RCNC suspensions. Results demonstrate the unique properties of DCNC, highlighting its application as a rheological modifier.

Rheology of cellulose nanocrystal and nanofibril suspensions

Nanocellulose is a sustainable nanomaterial and a versatile green platform that has attracted increasing attention. Although the wide applications of its aqueous suspensions are closely related to rheology, comprehensive studies of their rheological behavior, especially the yielding behavior, are still limited. Herein, to investigate the relationship between structure and rheological properties, the viscoelasticity, thixotropy and yielding behavior of two commonly used nanocelluloses, rod-shaped cellulose nanocrystals (CNCs) and filamentous cellulose nanofibrils (CNFs), were systematically investigated. The viscosity, viscoelasticity and thixotropic behavior of the suspensions were analyzed by steady-state shear, frequency sweep, creep-recovery, hysteresis loop, and three-interval thixotropic recovery tests. The yielding behaviors were evaluated through creep, steady-state shear, step shear rate, stress ramps, amplitude sweep, and large amplitude oscillatory shear tests. The rheological properties of the two typical suspensions showed a strong dependence on concentration and time. However, compared to CNC suspensions, CNF suspensions exhibited stronger thixotropy and higher yield stress due to the higher aspect ratio of CNF and the stronger structural skeleton of the suspensions as supported by Simha's equation and micromorphology analysis. This work provides a theoretical rheology basis for the practical applications of nanocellulose suspensions in various fields.

Liquid-crystalline assembly of spherical cellulose nanocrystals

Rod-shaped cellulose nanocrystals (CNCs), also called cellulose nanorods (CNRs), possess anisotropic properties that allow for their self-organization into chiral nematic liquid crystals. Interestingly, spherical cellulose nanocrystals (cellulose nanospheres, CNSs) have also been shown to form a chiral liquid-crystalline phase in recent years. Herein, to understand how the similar assembly takes places as particle dimension changes, the organization features of CNSs were investigated. Results of this study demonstrate that above a critical concentration in suspension, CNSs organize into a liquid-crystal phase consisting of periodically parallel-aligned layer structures. This structure persists after suspension drying. In comparison with CNRs, the alignment of CNSs exhibits a shorter layer distance, lower order degree, and weaker long-range orientation. To explain the early stages of tactoid formation, a “caterpillar-like” model was proposed, which was captured by freezing the CNS suspension in an intermediate aggregation state. This structure serves as the fundamental unit for further liquid-crystal assembly.

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.

Improved properties of polyvinyl alcohol films blended with aligned nanocellulose particles induced by a magnetic field

In this study, polyvinyl alcohol (PVA) films filled with nanocellulose particles were developed for food packaging. In particular, the effect of the weak magnetic field-induced alignment of the nanocellulose filler in PVA blended with rod-shaped cellulose nanocrystals (CNCs) and cellulose nanofibrils (CNFs) on the physicochemical properties of the respective blends was investigated. For the alignment of the nanocellulose particles (6% with respect to PVA), a film-forming solution of each blend was cast and a homogeneous magnetic field of the order of milli Tesla was applied during drying. Microscopic investigations were conducted to analyze the dispersion of the CNCs and CNFs in the PVA matrix. The influence of particle alignment was examined in terms of the microstructure, intermolecular interactions, crystallinity, and hydration state of the film, as well as water migration. The applied magnetic field induced the orientation of the nanocellulose fillers, leading to their improved dispersion in the PVA matrix. The uniform structure formed owing to the magnetically induced alignment of nanocellulose led to enhanced mechanical, barrier, and hydrophobic properties, as well as thermal stability of the two blends. The improvement was more evident for the CNC/PVA blend compared to the CNF/PVA one. The applied magnetic field decreased the fluidity of the film and increased the number of water molecules bound to PVA. When applied in the preservation of strawberries, the films exposed to a magnetic field facilitated better protection and firmness of the fruit.

Flexible Humidity Sensors Based on Multidimensional Titanium Dioxide/Cellulose Nanocrystals Composite Film.

A humidity sensor is a crucial device in daily life; therefore, in the present study, a novel humidity sensor was designed to increase its specific surface area to improve its humid sensing capacity and conductivity. Titanium dioxide nanoparticles (TiNP) consisting of zero-dimensional nanospheres and one-dimensional nanotubes were prepared by anodic oxidation. Rod-shaped cellulose nanocrystals (CNCs) with average length and diameter of 60 nm and 800 nm, respectively, were obtained by enzymatic hydrolysis and high pressure homogenization. TiNP/CNC composite films exhibited superior hydrophilicity and large specific surface areas based on Fourier transform infrared spectroscopy and nitrogen adsorption–desorption results. The humidity sensing characteristics of sensors based on TiNP/CNC flexible composite films with varying contents of TiNP were investigated under a relative humidity range of 11–97%. The 6% TiNP/CNC-based humidity sensor exhibited high humidity response, rapid response/recovery speed, and high stability. Furthermore, the humidity sensing mechanism of TiNP/CNC composite films was analyzed based on the density functional theory. TiNP/CNC-based humidity sensors could be applied in flexible and wearable electronics.

Cellulose nanocrystal/calcium alginate-based porous microspheres for rapid hemostasis and wound healing

Porous microsphere hemostatic materials, which possess rapid hemostatic, antibacterial, and wound healing-promotion properties, have key advantages over hemostatic dressings with a single hemostatic function. Using rod-shaped cellulose nanocrystals as the supporting framework, sodium alginate/cellulose nanocrystal porous microspheres (SA/CNC) were prepared using an inverse emulsion method. After SA/CNC self-assembly with the antibacterial polymer ε-polylysine, the hemostatic porous microspheres (PSLMs) showed high porosity, high liquid absorption capacity, and excellent coagulation properties. The in vitro and in vivo coagulation properties of PSLMs were evaluated and compared with those of the commercially available chitosan hemostatic powder. PSLMs had marked hemostatic effects in the following mouse hemorrhage models: caudal (81.20 s), liver (48.44 s), and femoral artery (71.66 s). After the introduction of ε-polylysine with excellent antibacterial properties to PSLMs, PSLMs effectively inhibited the activities of Escherichia coli, Staphylococcus aureus, and Pseudomonas aeruginosa.

Enhancing magnetic resonance imaging of bio-based nano-contrast via anchoring manganese on rod-shaped cellulose nanocrystals

Manganese-based nano materials used to enhance nano-contrasts in magnetic resonance imaging have low toxicity but suffer from a weak contrast imaging effect due to their low longitudinal relaxivity (r1). Moreover, the nanoparticle contrasts of manganese salt probably release manganese ions into the patient body during and after imaging process, causing potential toxicity problems. Thus, we took advantage of rod-shaped cellulose nanocrystals (CNCs) functionalized by diethylenetriamine pentaacetic dianhydride (coded as DCNCs) to anchor Mn2+ and improve its r1 for biocompatibility, highly chemical activity, and high specific area. Theoretical analysis indicated that the r1 could increase with the anchoring rate of Mn2+ on rod-shaped particles, and the large number of hydroxyl groups on CNCs made them able to carry as much as 5.9 mmol·g−1 of Mn2+. Then, we found the r1 increased linearly as the anchoring degree increased, up to 57.71 mM−1·s−1. The obtained DCNCs anchoring Mn2+ (Mn2+@DCNCs) nano-contrast showed low toxicity on RAW 264.7 and HUVEC, where the viability of the two cells was higher than 80%. Therefore, such a high r1 Mn2+-based material presents great advantage of commercial manganese and gadolinium contrasts, making the Mn2+@DCNCs of potential on diagnosing tumors and drug release.

Designing Highly Luminescent Cellulose Nanocrystals with Modulated Morphology for Multifunctional Bioimaging Materials.

Spherical cellulose nanocrystals (SCNs) and rod-shaped cellulose nanocrystals (RCNs) were extracted from different cellulose materials. The two shape forms of cellulose nanocrystals (CNs) were designed with a combination of isothiocyanate (FITC), and both the obtained FITC-SCNs and FITC-RCNs exhibited high fluorescence brightness. The surfaces of SCNs and RCNs were subjected to a secondary imino group by a Schiff reaction and then covalently bonded to the isothiocyanate group of FITC through a secondary imino group to obtain fluorescent cellulose nanocrystals (FITC-CNs). The absolute ζ-potential and dispersion stability of FITC-CNs (FITC-SCNs and FITC-RCNs) were improved, which also promoted the increase in the fluorescence quantum yield. FITC-RCNs had a fluorescence quantum yield of 30.7%, and FITC-SCNs had a morphological advantage (better dispersion, etc.), resulting in a higher fluorescence quantum yield of 35.9%. Cell cytotoxicity experiments demonstrated that the process of FITC-CNs entering mouse osteoblasts (MC3T3) did not destroy the cell membrane, showing good biocompatibility. On the other hand, FITC-CNs with good dispersibility can significantly enhance poly(vinyl alcohol) (PVA) and poly(lactic acid) (PLA); their mechanical properties were improved (the highest sample reached to 243%) and their fluorescent properties were imparted. This study provides a simple surface functionalization method to produce high-luminance fluorescent materials for bioimaging, multifunctional nanoenhancement/dispersion marking, and anticounterfeiting materials.

A Fenton-like System (Cu(II)/H2O2) for the Preparation of Cellulose Nanocrystals with a Slightly Modified Surface

A preparation process of cellulose nanocrystals using a Fenton-like system was presented. Rod-shaped cellulose nanocrystals were isolated after treatment in the H2O2/acetic acid/2–6 mol % copper acetate system. The morphology and sizes of rod-shaped particles were determined by AFM (atomic force microscopy) and cryo-EM (cryo-electron microscopy). X-ray diffraction proves that the prepared particles have a natural polymorphic modification of cellulose I with a high crystallinity index. Thermogravimetry data indicates a slight decrease in thermal stability of the particles when compared to starting cellulose, correlating with an increase in the number of carbonyl groups determined by chemical analysis. Using pK spectroscopy, active acid–base surface sites (pKi 5.5 and 7.9) were quantitatively determined. The cellulose nanoparticles formed stable hydrosols. Using photometry and dynamic light scattering, it has been established that the critical concentration of coagulation of sols is 76 mM KCl.

Enzymatically assisted isolation of high-quality cellulose nanoparticles from water hyacinth stems

High quality cellulose nanoparticles (CNP) were isolated from water hyacinth stem cellulose (Cel-WH) extracted via successive thermochemical and alkaline-peroxide treatments, and further enzymatically hydrolysed using the commercial cellulase complex, NS22086, at 50ºC. The maximum CNP concentration was reached after 120 min of enzymatic hydrolysis, with a hydrodynamic diameter in the order of 200−250 nm and an increase of 5% in crystallinity as compared with Cel-WH. The obtained rod-shaped cellulose nanocrystals, as revealed by atomic force microscopy (AFM), exhibited a nominal diameter of 15.6−29.4 nm, a length of 56−184.8 nm, and a height of 2.85−6.43 nm, indicating a low tendency to form aggregates. In the present study, it was found that water hyacinth stems are a valuable source for the isolation of high-quality CNP using an environmentally friendly procedure, with potential applications in nanomedicine and nanopharmacology.

Injectable and Magnetic Responsive Hydrogels with Bioinspired Ordered Structures.

Injectable hydrogels are particularly interesting for applications in minimally invasive tissue engineering and regenerative medicine strategies. However, the typical isotropic microstructure of these biomaterials limits their potential for the regeneration of ordered tissues. In the present work, we decorated rod-shaped cellulose nanocrystals with magnetic nanoparticles and coated these with polydopamine and polyethylene glycol polymer brushes to obtain chemical and colloidal stable nanoparticles. Then, these nanoparticles (0.1-0.5 wt %) were incorporated within gelatin hydrogels, creating injectable and magnetically responsive materials with potential for various biomedical applications. Nanoparticle alignment within the hydrogel matrix was achieved under exposure to uniform low magnetic fields (108 mT), resulting in biomaterials with directional microstructure and anisotropic mechanical properties. The biological performance of these nanocomposite hydrogels was studied using adipose tissue derived human stem cells. Cells encapsulated in the nanocomposite hydrogels showed high rates of viability demonstrating that the nanocomposite biomaterials are not cytotoxic. Remarkably, the microstructural patterns stemming from nanoparticle alignment induced the directional growth of seeded and, to a lower extent, encapsulated cells in the hydrogels, suggesting that this injectable system might find application in both cellular and acellular strategies targeting the regeneration of anisotropic tissues.

Transparency, moisture barrier property, and performance of the alternative solar cell encapsulants based on PU/PVDC blend reinforced with different types of cellulose nanocrystals

Two different types of cellulose nanocrystals, derived from water hyacinth fibers and microfibrillated cellulose (MFC), were prepared using an acid hydrolysis treatment. These cellulose nanocrystals (CNCs) were further used as barrier enhancing fillers for polyurethane (PU) blended with 25 wt% of poly(vinylidene dichloride) (PVDC). The aim of this study was to investigate the effects of types and concentration of CNCs on mechanical, optical and barrier properties of polymer composite films. The feasibility of applying the obtained composite films as an encapsulating material for enhancing the lifetime of dye sensitized solar cells (DSSC) was also of interest. The acid hydrolysis of the MFC-yielded rod-shaped cellulose nanocrystals (CNCm) while the acid-hydrolyzed water hyacinth led to a formation of spherical-shaped cellulose nanocrystals (CNCw). Regardless of the types of CNCs, the optical transparency of the composite films was maintained well above 60%. According to results in this study, the most efficient film with the lowest water vapor transmission rate of 0.0517 g m−2 day−1 was the PU/PVDC film reinforced with 0.1 wt% of CNCm. The encapsulants made from this composite could prolong the lifetime of the DSSC devices for up to 14 days, with the normalized PCE value of 0.78. Overall, this work showed that the considerations of the barrier properties of the polymer encapsulants alone are insufficient to ensure that the system would be effective. An interfacial adhesion between the encapsulants and the electrodes, as well as some side reactions between polymers and chemicals inside the fabricated cell, should also be taken into account.

Synthetic Strategies for the Fabrication of Cationic Surface-Modified Cellulose Nanocrystals

Cellulose nanocrystals (CNCs) are renewable nanosized materials with exceptional physicochemical properties that continue to garner a high level of attention in both industry and academia for their potential high-end material applications. These rod-shaped CNCs are appealing due to their non-toxic, carbohydrate-based chemical structure, large surface area, and the presence of ample surface hydroxyl groups for chemical surface modifications. CNCs, generally prepared from sulfuric acid-mediated hydrolysis of native cellulose, display an anionic surface that has been exploited for a number of applications. However, several recent studies showed the importance of CNCs’ surface charge reversal towards the design of functional cationic CNCs. Cationization of CNCs could further open up other innovative applications, in particular, bioapplications such as gene and drug delivery, vaccine adjuvants, and tissue engineering. This mini-review focuses mainly on the recent covalent synthetic methods for the design and fabrication of cationic CNCs as well as their potential bioapplications.

Human-based fibrillar nanocomposite hydrogels as bioinstructive matrices to tune stem cell behavior.

The extracellular matrix (ECM)-biomimetic fibrillar structure of platelet lysate (PL) gels along with their enriched milieu of biomolecules has drawn significant interest in regenerative medicine applications. However, PL-based gels have poor structural stability, which severely limits their performance as a bioinstructive biomaterial. Here, rod-shaped cellulose nanocrystals (CNC) are used as a novel approach to modulate the physical and biochemical microenvironment of PL gels enabling their effective use as injectable human-based cell scaffolds with a level of biomimicry that is difficult to recreate with synthetic biomaterials. The incorporation of CNC (0 to 0.61 wt%) into the PL fibrillar network during the coagulation cascade leads to decreased fiber branching, increased interfiber porosity (from 66 to 83%) and modulates fiber (from 1.4 ± 0.7 to 27 ± 12 kPa) and bulk hydrogel (from 18 ± 4 to 1256 ± 82 Pa) mechanical properties. As a result of these physicochemical alterations, nanocomposite PL hydrogels resist the typical extensive clot retraction (from 76 ± 1 to 24 ± 3 at day 7) and show favored retention of PL bioactive molecules. The feedback of these cues on the fate of human adipose-derived stem cells is evaluated, showing how it can be explored to modulate the commitment of encapsulated stem cells toward different genetic phenotypes without the need for additional external biological stimuli. These fibrillar nanocomposite hydrogels allow therefore the exploration of the outstanding biological properties of human-based PL as an efficient engineered ECM which can be tailored to trigger specific regenerative pathways in minimal invasive strategies.

Preparation and characterization of nanocellulose reinforced semi-interpenetrating polymer network of chitosan hydrogel

Semi-interpenetrating polymer network hydrogels with improved mechanical properties and remarkable sensitivity toward pH changes were prepared using chitosan reinforced with cellulose nanocrystals (CNCs). Glutaraldehyde was used as a crosslinker because of its high reactivity toward the amine groups of chitosan. In this study, rod-shaped CNCs that were approximately 200–300 nm in length and 40–50 nm in width were prepared from microcrystalline cellulose via sulfuric acid hydrolysis. CNC ratios of 0, 0.5, 1, 1.5, 2, and 2.5% were selected to study the effects of CNCs on the mechanical properties and swelling behavior of the chitosan hydrogel. The crosslinking reaction between chitosan and glutaraldehyde was confirmed by the presence of a –C=N stretching group at 1548 cm−1 in the Fourier transform infrared spectrum of chitosan hydrogel. The crosslinking degree of the chitosan hydrogel was 83.6%. The X-ray diffraction patterns confirmed that adding CNCs induced a combination of amorphous and crystalline regions in the hydrogel matrix. Mechanical tests showed that the maximum compression of the chitosan hydrogel increased from 25.9 ± 1 to 50.8 ± 3 kPa with increasing CNC content from 0 to 2.5%. CNC-chitosan hydrogels exhibited excellent pH sensitivity and producing the maximum swelling ratio under acidic condition (pH 4.01). On the basis of the results of this study, we assume that the improved mechanical properties and excellent pH sensitivity of the CNC-chitosan hydrogels will expand their application scopes in various fields, such as tissue engineering, pharmaceuticals, and drug delivery.

Temperature-Responsive Nanofibrillar Hydrogels for Cell Encapsulation.

Natural extracellular matrices often have a filamentous nature, however, only a limited number of artificial extracellular matrices have been designed from nanofibrillar building blocks. Here we report the preparation of temperature-responsive nanofibrillar hydrogels from rod-shaped cellulose nanocrystals (CNCs) functionalized with a copolymer of N-isopropylacrylamide and N,N'-dimethylaminoethyl methacrylate. The composition of the copolymer was tuned to achieve gelation of the suspension of copolymer-functionalized CNCs at 37 °C in cell culture medium and gel dissociation upon cooling it to room temperature. The mechanical properties and the structure of the hydrogel were controlled by changing copolymer composition and the CNC-to-copolymer mass ratio. The thermoreversible gels were used for the encapsulation and culture of fibroblasts and T cells and showed low cytotoxicity. Following cell culture, the cells were released from the gel by reducing the temperature, thus, enabling further cell characterization. These results pave the way for the generation of injectable temperature-responsive nanofibrillar hydrogels. The release of cells following their culture in the hydrogels would enable enhanced cell characterization and potential transfer in a different cell culture medium.

Interfacial properties of cellulose nanoparticles obtained from acid and enzymatic hydrolysis of cellulose

Rod-shaped cellulose nanocrystals obtained by acid hydrolysis of eucalyptus fibers (CNCa) presented high aspect ratio (estimated length and width of 180 and 5 nm, respectively) and zeta potential of −(17 ± 1) mV at pH 6. This typical morphology of cellulose nanocrystals was in contrast to nanoparticles obtained upon enzymatic hydrolysis of bacterial cellulose (CNCe), which were asymmetric and irregular due to surface-bound cellulases and presented a distinctive surface roughness. Interestingly, CNCe also displayed axial grooves, to yield a C-shape cross section that has not been reported before. The effect of the characteristic shape and surface chemistry of CNCa and of grooved CNCe was studied at oil/water interfaces and solid surfaces. Emulsions (20 % v/v oil) prepared with the CNCa were more stable than those prepared with CNCe, owing to their characteristic shape and surface chemistry. Hydrophilic (silica surfaces cationized by pre-adsorbed polycation) and hydrophobic (polystyrene films) solid surfaces were used as substrates for the adsorption of CNCe and CNCa for each type of surface. The ellipsometric data and AFM images indicated larger affinity of CNCe than CNCa for the hydrophobic surface. On the other hand, CNCa formed homogeneous monolayer on hydrophilic surfaces, whereas CNCe formed discontinuous films. Sequential adsorption behavior of CNCa on CNCe layers (or vice versa) suggested that the interaction between them is controlled by the orientation of enzymes bound to CNCe.

Flocculation of bacteria by depletion interactions due to rod-shaped cellulose nanocrystals

We report depletion induced flocculation and phase separation of bacteria due to the presence of rod-shaped nanoparticles by using confocal laser microscopy and turbidity measurements. To investigate the depletion effect of rod shaped nanoparticles in bacteria systems, cellulose nanocrystals with length, L=90±10nm, diameter, D=8±1nm and zeta potential of 51.5±0.8mV was used. The flocculation of the Gram-negative bacterium Pseudomanas aeruginosa (average length=1.2μm, width=0.2μm) was tested. The zeta potential of P. aeruginosa suspended in 10mM NaCl was −29.84±0.6mV. Bacterial flocculation was observed at the CNC concentration of less than 0.1% due to the depletion effect. We conclude from our results that rod shaped nanoparticles are very effective for the depletion flocculation of colloidal size bacteria and that phase separation of bacteria can occur at very low concentrations of rodlike CNC particles.

Suspension viscosities and shape parameter of cellulose nanocrystals (CNC)

The successful application of nanoscale materials requires an accurate description of the shape and size of the nanomaterial. Cellulose nanocrystals (CNC) are a plant-derived nanomaterial that is currently being investigated for a variety of applications. We have developed here a method to determine the shape parameter (length/diameter) of rod-like CNC particles using bulk viscosity measurements of CNC solutions. The cellulose nanocrystals were prepared by concentrated sulfuric acid hydrolysis of wood pulp. CNC particles in aqueous solutions carry negative electrical charges due to the sulfate surface groups and showed electroviscous effects. The viscosities of cellulose nanocrystals suspensions were measured at various NaCl electrolyte concentrations and intrinsic viscosities were calculated. The extrapolation of intrinsic viscosity to 1 nm Debye length was used to calculate intrinsic viscosity of hard rods without electroviscous effects. The corresponding shape factor calculated from Simha's equation was 41. Atomic force microscopy (AFM) was used to measure the shape parameter of individual CNC particles. Limited number of measurements yielded an average value of 30. Intrinsic viscosity measurements would be a reliable and relatively simple method to calculate the shape factor of rod-shaped cellulose nanocrystals after electroviscous effects are corrected.