Surface Modification Of Cellulose Nanocrystals Research Articles

Inverse Pickering emulsion stabilized by modified cellulose nanocrystals for drilling fluid application

With the rise in oil consumption, the production and exploration of oil have increasingly targeted unconventional reservoirs. Oil-based drilling fluids (ODFs) are well-suitable for unconventional reservoirs because of their superior wellbore stability, strong lubrication, and great resistance to contamination. Inverse (water-in-oil, W/O) emulsions have the ability to lower the oil content in conventional ODFs through the addition of water, leading to more cost-effectiveness and eco-friendliness. However, inverse emulsions require the introduction of a large amount of surfactants to stabilize the oil/water interface, which led to environmental pollution. To address these issues, surface modified cellulose nanocrystals (C14-CNCs) were prepared through acylation modification and then used as solid stabilizers to prepare a high-performance inverse Pickering emulsion-based drilling fluid (IPEDF), in which sunflower seed biodiesel was chosen as the oil phase, and organobentonite (i.e., low polarity SD-1 and high polarity SD-2) was used as a viscosifier and filtration loss reducer. The stability and structure of Pickering emulsion can be controlled by altering the hydrophilicity of C14-CNCs through adjusting the reaction time of acylation. Through optimization of the polarity of organobentonite and the hydrophilicity of C14-CNCs, the as-formulated IPEDF exhibits superior shear-thinning behavior, thixotropy, and filtration property. This work provides a promising avenue for using biomass-derived nanomaterials as stabilizers for the high-performance inverse Pickering emulsion drilling fluids.

Functional electrospun polylactic acid core-shell thermochromic fibers with modified cellulose nanocrystals for enhanced temperature-responsive applications

Core-shell electrospun fibers with thermochromic materials are suitable for temperature sensing due to their customizable properties. However, the beneficial effect of bio-based thermochromic fibers incorporating sustainable nanomaterials needs to be further demonstrated, especially regarding their thermal stability and mechanical properties. In this study, core-shell structured nanofibers were produced through a co-axial electrospinning process using polylactic acid (PLA) and surface-modified cellulose nanocrystals (mCNCs) as the shell, and crystal violet lactone (CVL), bisphenol A, and 1-dodecanol as the core. Chemical characterization confirmed the successful grafting of vinyl siloxane within mCNCs, enhancing CNC dispersion in the PLA matrix. The thermochromic fibers exhibited smooth, uniform surfaces, with minimal impact of mCNCs on the glass transition temperature (Tg). Compared with neat electrospun PLA fibers, mCNC-added fibers showed improved thermal stability. Although the core material negatively affected mechanical properties, mCNCs enhanced tensile strength and Young’s modulus. The fibers demonstrated rapid and sensitive responses to temperature changes from 0 to 20 ˚C, indicating their potential as effective temperature sensors with improved properties.

Grafting Kinetics and Compatibility Simulation in Surface Modification of Cellulose Nanocrystals with Poly(lactic acid) for Composites

Grafting Kinetics and Compatibility Simulation in Surface Modification of Cellulose Nanocrystals with Poly(lactic acid) for Composites

How surface modification of cellulose nanocrystals affects the crystallization process of poly (β-hydroxybutyrate)

Hydroxyl groups on the surface of cellulose nanocrystals (CNC) are modified by chemical methods, CNC and the modified CNC are used as fillers to prepare PHB/cellulose nanocomposites. The absorption peak of carbonyl group of the modified CNC (CNC-CL and CNC-LA) appears in the FT-IR spectra, which proves that the modifications are successful. Thermal stability of CNC-CL and CNC-LA is better than that of pure CNC. Pure CNC is beneficial to the nucleation of PHB, while CNC-CL and CNC-LA inhibit the nucleation of PHB. The spherulite size of PHB and its nanocomposites increases linearly over time, and the maximum growth rate of PHB spherulite exists at 90 °C. Rheological analysis shows that viscous deformation plays the dominant role in PHB, PHBC and PHBC-CL samples, while the elastic deformation is dominant in PHBC-LA. According to the rheological data, the dispersion of CNC-CL and CNC-LA in PHB is better than that of CNC. This work demonstrates the impact of modified CNC on the crystallization and viscoelastic properties of PHB. Moreover, the interface enhancement effect of modified CNC on PHB/CNC nanomaterials is revealed from the crystallization and rheology perspectives.

Mechanochemical modification of cellulose nanocrystals by tosylation and nucleophilic substitution

A mechanochemical solvent-free method enables facile access to surface modified cellulose nanocrystals, through activation and versatile nucleophilic substitution.

A Review of Modified Cellulose Nanocrystals and their Applications

Abstract: Cellulose is one of the most abundant natural polymers developed in the ecosystem and has been used in many applications for industrial products since ancient times. Although the main sources of cellulose are wood plant, fibers and, additional sources can also be discovered, such as algae, fungi, bacteria, and even some marine organisms (such as tunicates). Mechanical or chemical processes are used to transform cellulosic materials into cellulose nanocrystals due to their efficacy, high aspect ratio, low density, renewability, and non-toxicity. They have drawn a lot of attention in a variety of industries. Here, we discuss various applications and properties in particular mechanical, rheological, liquid crystalline nature, and adhesives to introduce cellulose nanocrystals hydrophilic, colloidal stable, and rigid rod-shaped bio-based nanomaterial with high strength and high surface area. Under various circumstances, it improves the characteristics of various compounds. The grafting of polymers on the surface of cellulose nanocrystals has attracted significant interest in both academia and industry due to the rapidly expanding number of potential applications of surface-modified cellulose nanocrystals, which range from building blocks in nanocomposites and responsive nanomaterials to antimicrobial agents. Furthermore, we explore the most popular polymerization methods, such as surface-initiated ring-opening polymerization, surface-initiated free radical polymerization, surface-initiated atom transferred radical polymerization and surface-initiated controlled radical polymerization that are employed to graft polymers from the surface and reducing end groups of cellulose nanocrystals. In this review, we examine the available literature and provide a summary of recent applications of cellulose nanocrystals, including biomedical application, drug delivery, biosensor, tissue engineering, antibacterial activity, wound healings, etc.

Surface modification of cellulose nanocrystals by physically adsorbing lactoferrin as pickering stabilizers: Emulsion stabilization and in vitro lipid digestion

Surface modification is a prerequisite procedure for using cellulose nanocrystals (CNCs) in food and other industries. This study reports a simple and safe procedure for CNCs surface modification using physically absorbing food protein (lactoferrin, LF) that could improve the emulsification performance and modulating emulsion lipid digestion in vitro. Modification of CNCs by LF was characterized by adsorption percentage (%), zeta-potential, atom force microscopy, and contact angle. The modification occurred electrostatically between negatively CNCs and positively LF. LF-modified CNCs are more hydrophobic and aggregation-prone depending on the ratio of protein to CNCs and pH. Emulsions stabilized by LF-modified CNCs which are characterized by visual appearance, microstructure, droplet size, and stability against lipid oxidation. Modification of CNCs by LF could improve the emulsification performance of CNCs and show high stability against lipid oxidation. In vitro gastrointestinal digestion of emulsions stabilized by LF-modified CNCs was also investigated by Free fatty acid released (FFA, %) and microstructure. Overall, emulsions stabilized by CNCs particles have lower lipid digestion extent than that of tween 20. The findings would have potential applications in fabrication of novel functional emulsions in food and other industries.

Surface Modification of Cellulose Nanocrystals (CNCs) to Form a Biocompatible, Stable, and Hydrophilic Substrate for MRI

This study focused on surface modification of cellulose nanocrystals (CNCs) to create a biocompatible, stable, and hydrophilic substrate suitable for use as a coating agent to develop a dual-contrast composite material. The CNCs were prepared using acid hydrolysis. Hydrolysis was completed using 64% sulfuric acid at 45 °C for 1 h, which was combined with polyethylene glycol and sodium hydroxide (PEG/NaOH). The yield of samples exhibited prominent physicochemical properties. Zeta (ζ) potential analysis showed that the CNCs sample had excellent colloidal stability with a highly negative surface charge. Transmission electron microscopy (TEM) analysis confirmed that the CNCs sample had a rod-like morphology. On the other hand, field-emission scanning electron microscopy (FESEM) analysis showed that the acid hydrolysis process caused a significant reduction in particle size and changed surface morphology. In addition, cellulose nanocrystals with polyethylene glycol and sodium hydroxide (CNCs-PEG/NaOH) have many noteworthy properties such as colloidal stability, small hydrodynamic size, and water dispersibility. Furthermore, the MTT assay test on Hep G2 cells demonstrated good biocompatibility of the CNCs-PEG/NaOH and did not exhibit any cytotoxic effects. Hence, CNCs-PEG/NaOH holds the potential to serve as a dual-contrast agent for MRI techniques and other biomedical applications.

Cover Feature: Chirality Transfer from an Innately Chiral Nanocrystal Core to a Nematic Liquid Crystal 2: Lyotropic Chromonic Liquid Crystals (ChemPhysChem 3/2023)

The Cover Feature illustrates the formation of homochiral nematic lyotropic chromonic liquid crystal tactoids formed by disodium cromoglycate in water by the addition of cromoglycate surface-modified cellulose nanocrystals (CNCs) as chiral solutes. Using CNCs with an inherently chiral core reveals that biorenewable chiral solutes can serve as suitably powerful and increasingly multipurpose chiral additives. More information can be found in the Research Article by Diana P. N. Gonçalves, Timothy Ogolla, and Torsten Hegmann.

Effect of decoration route on the nanomechanical, adhesive, and force response of nanocelluloses-An in situ force spectroscopy study.

Although cellulose derivatives are widely applied in high-tech materials, the relation between their force responses and their surface chemical properties in a biological environment as a function of pH is unknown. Here, interaction forces of surface modified cellulose nanocrystals (CNCs), lignin residual cellulose nanocrystals (LCNCs), and 2,2,6,6-tetramethylpiperidine-1-oxyl radical (TEMPO)-oxidized cellulose nanofibres (TCNFs) with OSO3-, COO- and lignin chemical groups were measured using in situ peak force quantitative nanomechanical mapping and force spectroscopy in salt solution at two pH values. We found that the forces acting between the tip and CNC or LCNC are steric dominated showing long range and slow decay as a result of their low surface charge density. High Mw lignin contributed to the increased repulsion range for LCNCs compared to CNCs. The repulsion measured for TCNFs at the very short range was electrostatic force dominating showing a steep decay attributed to its high surface charge density. In the case of TCNFs, electrostatic double layer force was also evidenced by the attraction measured at secondary minima. In all the three cases the electro steric interactions are pH dependent. Dissipation maps verified that the force behavior for each material was related to structural conformation restriction of the groups at compression. The slow decayed repulsion of CNCs or LCNCs is related to a weak restriction of conformational change due to small surface groups or high molecular weight bound polymers forming flat layers, whereas the steep repulsion of TCNFs is attributed to a strong conformation restriction of carboxylic groups occurred by forming extended structure. Our results suggest that the force responses of the materials were dominated by surface charges and structural differences. TCNFs showed superior nanomechanical and repulsion properties over CNCs or LCNCs at neutral pH.

Chirality Transfer from an Innately Chiral Nanocrystal Core to a Nematic Liquid Crystal 2: Lyotropic Chromonic Liquid Crystals.

The importance of and the difference between molecular versus structural core chirality of substances that form nanomaterials, and their ability to transmit and amplify their chirality to and within a surrounding condensed medium is yet to be exactly understood. Here we demonstrate that neat as well as disodium cromoglycate (DSCG) surface-modified cellulose nanocrystals (CNCs) with both molecular and morphological core chirality can induce homochirality in racemic nematic lyotropic chromonic liquid crystal (rac-N-LCLC) tactoids. In comparison to the parent chiral organic building blocks, D-glucose, endowed only with molecular chirality, both CNCs showed a superior chirality transfer ability. Here, particularly the structurally compatible DSCG-modified CNCs prove to be highly effective since the surface DSCG moieties can insert into the DSCG stacks that constitute the racemic tactoids. Overall, this presents a highly efficient pathway for chiral induction in an aqueous medium and thus for understanding the origins of biological homochirality in a suitable experimental system.

Martini 3 model of surface modified cellulose nanocrystals: investigation of aqueous colloidal stability

The Martini coarse-grained force field is one of the most popular coarse-grained models for molecular dynamics (MD) modelling in biology, chemistry, and material science. Recently, a new force field version, Martini 3, had been reported with improved interaction balance and many new bead types. Here, we present a new cellulose nanocrystal (CNC) model based on Martini 3. The calculated CNC structures, lattice parameters, and mechanical properties reproduce experimental measurements well and provide an improvement over previous CNC models. Then, surface modifications with COO− groups and interactions with Na+ ions were fitted based on the atomistic MD results to reproduce the interactions between surface-modified CNCs. Finally, the colloidal stability and dispersion properties were studied with varied NaCl concentrations and a good agreement with experimental results was found. Our work brings new progress toward CNC modelling to describe different surface modifications and colloidal solutions that were not available in previous coarse-grained models.Graphical abstract

Surface modifications of cellulose nanocrystals: Processes, properties, and applications

The interest in nanocellulose has recently increased in many fields due to its natural abundance, exceptional mechanical/optical properties, and better biocompatibility. During the production of cellulose nanocrystals (CNCs) via sulfuric acid hydrolysis, sulfate groups are introduced, which decrease the thermal stability of CNCs and, thus, have a profound negative effect on the potential application of CNCs in nanocomposites. Also, mechanical methods exhibit poor morphological properties in CNCs with a reduced degree of crystallinity. Therefore, to improve the processability and performance of CNCs and extend their industrial applications and quality, nano-cellulose undergoes surface modifications by physical and chemical means. Surface modifications of CNCs lower the surface energy, increase hydrophobicity, improve interfacial adhesion, enhance their compatibility between nanocomposite components, and improve their dispersion and interaction. Surface-modified CNCs have wide applications in medicine, catalysis, optics, remediation processes, electronics, textiles, pulp, paper, etc. Other applications of CNCs are: supporting catalysts and sensors, as diaphragms in earphones; for tissue engineering, scaffolds, for toughened paper, as polymer nanocomposites for developing membranes, in flexible panels for flat panel displays, in the optical application and biomimetic foams, and as rheology modifiers. This review provides the latest advances in surface modification of CNCs and the relevant processes, properties, and applications. • Acid hydrolysis of cellulose introduces sulfate groups on cellulose nanocrystals (CNCs) surface, limiting their applications. • Surface modification is an effective method to mitigate the shortcomings of CNCs. • Recent advancements in physical and chemical surface modifications are summarized. • The applications of CNCs, including polymer nanocomposites, are intensively studied.

Highly crystallized and tough polylactic acid through addition of surface modified cellulose nanocrystals

AbstractTo prepare a fully organic polylactic acid (PLA)‐based bio‐nanocomposite, cellulose nanocrystals (CNCs) were grafted by PLA through ring‐opening polymerization (ROP) of L‐lactide monomers onto CNCs. The grafting process was evaluated by 1HNMR and FTIR spectroscopic methods. The effect of surface‐modified CNCs (M‐CNCs) was investigated on thermal, mechanical, rheological, and dynamic mechanical thermal properties of PLA. The M‐CNCs were successfully dispersed in the PLA matrix. Isothermal and non‐isothermal DSC studies revealed that M‐CNCs caused an intensive increase in crystallization kinetics and therefore nucleation density and crystallization extent. DSC, XRD, and DMTA analyses indicated the formation of different crystal structures [α, α', β] in PLA after addition of M‐CNCs. Rheological analysis was carried out for microstructural investigation of the nanocomposites. Interestingly, after the addition of M‐CNCs not only the tensile strength and modulus of the samples increased but also the toughness of PLA was considerably improved.

Cellulose nanocrystals modification by grafting from ring opening polymerization of a cyclic carbonate

Surface modification of cellulose nanocrystals (CNC) by organocatalysed grafting from ring-opening polymerization (ROP) of trimethylene carbonate was investigated. Organocatalysts including an amidine (DBU), a guanidine (TBD), an amino-pyridine (DMAP) and a phosphazene (BEMP) were successfully assessed for this purpose, with performances in the order TBD > BEMP > DMAP, DBU. The grafting ratio can be tuned by varying the experimental parameters, with the highest grafting of 74 % by weight obtained under mild conditions, i.e at room temperature in tetrahydrofuran with a low amount of catalyst. This value is much higher than that of typical ring opening polymerizations of cyclic esters initiated from the surface of cellulose nanoparticles. Additionally, DSC analysis of the modified material revealed the presence of a glass transition temperature, indicative of a sufficient graft length to display polymeric behaviour. This is, to our knowledge, the first example of cellulose nanocrystals grafted with polycarbonate chains.

Fabrication of cellulose nanocrystals (CNCs) in choline chloride-citric acid (ChCl-CA) solvent to lodge antimicrobial activity

Surface-modified cellulose nanocrystals (CNCs) have gained substantial interest in industry. The renewability and abundance of the raw material to prepare CNCs make them a promising green material. In this study, two types of CNCs were prepared by sulfuric acid (H2SO4) and stepwise H2SO4 and choline chloride-citric acid (ChCl-CA) deep eutectic solvent-like (DES) treatments. The DES treatment led to esterification and further degradation of the CNCs. The obtained nanoparticles were distributed in size range of 50 nm to 500 nm and 20 nm to 70 nm for the H2SO4 and stepwise treatments, respectively. The effects of the nanoparticles on the mechanical properties, thermal stability, and antibacterial activity of poly(vinyl alcohol) (PVOH) were determined using a universal mechanical testing machine, thermogravimetric analysis (TGA), and the agar diffusion method. The results indicated that nanoparticles had good compatibility in PVOH at a concentration below 10%. The CNCs had greater effect on the mechanical properties and the thermal stability of films than the esterified CNCs. However, the CA modified CNCs showed more favorable antibacterial activity than the CNCs from H2SO4 treatment. Taking the mechanical properties, the thermal stability, and the antibacterial activity into consideration, 5% was selected as a suitable concentration for composite film preparation.

Properties of Poly(3-hydroxybutyrate-co-3-hydroxyvalerate)/Polycaprolactone Polymer Mixtures Reinforced by Cellulose Nanocrystals: Experimental and Simulation Studies.

Poly(3-hydroxybutyrate-co-3-hydroxyvalerate)/polycaprolactone (PHBV/PCL) polymer mixtures reinforced by cellulose nanocrystals (CNCs) have been obtained. To improve the CNC compatibility with the hydrophobic PHBV/PCL matrix, the CNC surface was modified by amphiphilic polymers, i.e., polyvinylpyrrolidone (PVP) and polyacrylamide (PAM). The polymer composites were characterized by FTIR, DSC, TG, XRD, microscopy, BET surface area, and tensile testing. The morphological, sorption, thermal, and mechanical properties of the obtained composites have been studied. It was found out that with an increase in the CNC content in the composites, the porosity of the films increased, which was reflected in an increase in their specific surface areas and water sorption. An analysis of the IR spectra confirms that hydrogen bonds can be formed between the CNC hydroxyl- and the –CO– groups of PCL and PHBV. The thermal decomposition of CNC in the PHBV/PCL/CNC composites starts at a much higher temperature than the decomposition of pure CNC. It was revealed that CNCs can either induce crystallization and the polymer crystallite growth or act as a compatibilizer of a mixture of the polymers causing their amorphization. The CNC addition significantly reduces the elongation and strength of the composites, but changes Young’s modulus insignificantly, i.e., the mechanical properties of the composites are retained under conditions of small linear deformations. A molecular-dynamics simulation of several systems, starting from simplest binary (solvent-polymer) and finishing with multi-component (CNC—polymer mixture—solvent) systems, has been made. It is concluded that the surface modification of CNCs with amphiphilic polymers makes it possible to obtain the CNC composites with hydrophobic polymer matrices.

Surface modification of cellulose nanocrystals via SI-AGET ATRP and application in waterborne coating for removing of formaldehyde

The hazardous indoor air pollutants of formaldehyde (HCHO) are harmful for human health. Nowadays, it is important to design and fabricate green and efficient HCHO removal materials for HCHO removal from polluted indoor air. In this manuscript, cellulose nanocrystals (CNCs) as green nanomaterials were successfully surface-initiated by 2-(methacryloyloxy)ethyl acetoacetate (MEAA) as functional monomer via surface-initiated Activator Generated by Electron Transfer Atom Transfer Radical Polymerization (SI-AGET ATRP) for the application in removal of HCHO. The employment of CNCs/Poly(2-(methacryloyloxy)ethyl acetoacetate) (CNCs@PMEAA) as nanocomposites were further implanted self-healing waterborne coating for an effective way to remove HCHO. From the result, the HCHO removal efficiency reached 97.5% of CNCs@PMEAA-type coating within 300 min at room temperature, which was much higher than that of the conventional coating (82.8%). This study provides some promising green methods for designing nanocomposite's waterborne coating to remove HCHO at room temperature.

Cellulose nanocrystals supported—PolyHIPE foams for low‐temperature latent heat storage applications

AbstractParaffin‐based shape‐stabilized composite phase change materials (PCM) containing surface modified cellulose nanocrystals (CNCs) for thermal energy storage applications were prepared. In this respect, a three‐step experimental procedure consisting nanoparticle modification, macroporous foam synthesis, and composite PCM preparation was implemented. While CNCs were modified via freeze‐templating, high internal phase emulsion (HIPE) templating was used for the synthesis of polymeric foams ‐ known as polyHIPEs. Meanwhile a simple method was applied to impregnate n‐hexadecane (HD), which is a paraffin‐based PCM within the polyHIPE foam matrix. It was demonstrated that surface modified CNCs can be efficiently used to prepare polyHIPE foams with improved properties. It was also shown that the impregnation of HD into the ‐polyHIPE foam matrix supported by CTAB‐CNCs can be achieved with an incorporation rate of up to 55.7%. Moreover, the phase transition temperature and thermal energy storage capacity of the obtained composite PCM was determined as 22.7°C and 117 J/g, respectively.

Surface modification of cellulose nanocrystals towards new materials development

AbstractCellulose nanocrystals (CNCs) are a kind of sustainable nanoparticle from biomass, which are widely used as reinforcing filler and assembly building block for high‐performance composites and function materials including biomaterial, optics, and so forth. Here, their unique advantages in material applications were reviewed based on their rod‐like morphology, crystalline structure, dimension‐related effects, and multi‐level order structure. Then, we focused on the molecular engineering of CNCs, including the structure and physicochemical properties of their surface, along with surface modification methods and steric effects. We further discussed the performance‐improvement and functionalization methods based on multi‐component complex systems, together with the effects of surface molecular engineering on the performance and functions. Meanwhile, methods of optimizing orientation in uniaxial arrays were discussed along with those of enhancing photoluminescence efficiency via surface chemical modification and substance coordination. In the end, we prospected the design, development, and construction methods of new CNCs materials.