Fabrication of PMMA nanocomposite biomaterials reinforced by cellulose nanocrystals extracted from rice husk for dental applications

The primary objective of global studies is to develop the properties and durability of polymers for various applications.When it comes to dental disability,denture base materials must have sufficient mechanical and tribological performance in order to withstand the forces experienced in the mouth.This work aims to investigate the effects of the addition of low content of cellulose nanocrystals(CNC)on the mechanical and tribological performance of the polymethyl methacrylate(PMMA)nanocomposites.Different weight percent of CNC(0,0.2,0.4,0.6,and 0.8 wt%)were added to the PMMA matrix followed by ball milling to evenly distribute the nanoparticles reinforced phase in the matrix phase.The findings emphasize the significant impact of CNC integration on the performance of PMMA nanocomposites.By increasing the content of the CNC nanoparticles,the mechanical properties of PMMA were improved.In addition,the tribological outcomes demonstrated a significant reduction in the friction coefficient besides an enhancement in the wear resistance as the weight percentage of nanoparticles increased.The surface of the worn samples was investigated by utilizing SEM to identify the wear mechanisms corresponding to the different compositions.In addition,a finite elment model(FEM)was developed to ascertain the thickness of the worn layer and the generated stressed on the surfaces of the nanocomposite throughout the friction process.

Isolative Synthesis and Characterization of Cellulose and Cellulose Nanocrystals from Typha angustifolia

The application potential of cellulosic materials in natural composites and other fields needs to be explored to develop innovative, sustainable, lightweight, functional biomass materials that are also environmentally friendly. This study investigated Typha angustifolia (Typha sp.) as a potential new raw material for extracting cellulose nanocrystals (CNCs) for application in wastewater treatment composites. Alkaline treatments and bleaching were used to remove cellulose from the stem fibres. The CNCs were then isolated from the recovered cellulose using acid hydrolysis. The study showed a few distinct functional groups (O-H, -C-H, =C-H and C-O, and C-O-C) in the Fourier Transform Infrared (FTIR) spectra. A scanning electron microscope (SEM) revealed the smooth surface of CPC and CNCs, which resulted from removing lignin and hemicellulose from powdered Typha angustifolia. Based on the crystalline index, the powdered Typha angustifolia, CPC, and CNCs were 42.86%, 66.94% and 77.41%. The loss of the amorphous section of the Typha sp. fibre resulted in a decrease in particle size. It may be inferred from the features of a Typha sp. CNC that CNCs may be employed as reinforcement in composites for wastewater treatment.

Surface-functionalized cellulose nanocrystals(CNC)and synergisms with surfactant for enhanced oil recovery in low-permeability reservoirs

Nanocellulose,a natural polymeric nanomaterial,has attracted significant attention in enhanced oil recovery(EOR)applications due to its abundance,nanoscale,high oil-water interfacial adsorption ef-ficiency.In this study,surface-functionalized cellulose nanocrystals(SF-CNCs)were prepared via hy-drochloric acid hydrolysis and chemical modification,with adaptable nanosize and considerable dispersion stability in low-permeability reservoirs.The SF-CNCs were structurally characterized by FT-IR,Cryo-TEM,which have a diameter of 5-10 nm and a length of 100-200 nm.The SF-CNC dispersions possessed higher stability and stronger salt-tolerance than those of corresponding CNC dispersions,due to the strong hydrophilicity of the sulfonic acid group.It was synergistically used with a non-ionic surfactant(APG1214)to formulate a combined flooding system(0.1 wt%SF-CNC+0.2 wt%APG1214).The combined flooding system exhibits strong emulsification stability,low oil-water interfacial tension of o.03 mN/m,and the ability to alter the wettability for oil-wetting rocks.Furthermore,the combined system was_able to provide an optimum EOR efficiency of 20.2%in low-permeability cores with 30.13×10^(-3)μm^(2).Notably.it can enlarge the sweep volume and increase the displacement efficiency simultaneously.Overall,the newly formulated nanocellulose/surfactant combined system exhibits a remarkable EoR performance in low-permeability reservoirs.

Interconnected and high cycling stability polypyrrole supercapacitors using cellulose nanocrystals and commonly used inorganic salts as dopants

Polypyrrole(PPy)is wildly used as electrode material in supercapacitors due to its high conductivity,low cost,ease of handling,and ease of fabrication.However,limited capacitance and poor cycling stability hinder its practical application.After developing carboxylated cellulose nanocrystals(CNC-COO^(-))as immobile dopants for PPy to improve its cycling stability,we investigated the effect of different commonly used salts(KCl,NaCl,KBr,and NaClO_(4))as dopants during electrode fabrication by electropolymerization.The film’s capacitance increased from 160.6 to 183.4 F g^(-1)after adding a combination of KCl and NaClO_(4) into the electrodeposition electrolyte.More importantly,the porous and interconnected PPy/CNC-COO^(-)-Cl-(Cl O_(4)^(-))_0.5 electrode film exhibited an excellent capacitance of 125.0 F g^(-1)(0.78 F cm^(-2))at a high current density of 2.0 Ag^(-1)(20 m A cm^(-2),allowing charging in less than 1 min),increasing almost 204%over PPy/CNC-COO-films.A symmetric PPy/CNC-COO^(-)-Cl-(ClO_(4)^(-))_0.5 supercapacitor retained its full capacitance after 5000 cycles,and displayed a high energy density of 5.2 Wh kg^(-1)at a power density of 25.4 W kg^(-1)(34.5μWh cm^(-2) at 1752.3μW cm^(-2)).These results reveal that the porous structure formed by doping with CNC-COO-and inorganic salts opens up more active reaction areas to store charges in PPy-based films as the stiff and ribbon-like CNC-COO-as permanent dopants improve the strength and stability of PPy-based films.Our demonstration provides a simple and practical way to deposit PPy based supercapacitors with high capacitance,fast charging,and excellent cycling stability.

Edible Coatings Based on Apple Pectin,Cellulose Nanocrystals,and Essential Oil of Lemongrass:Improving the Quality and Shelf Life of Strawberries(Fragaria Ananassa)

In this work,nine different types of edible coating based on pectin,cellulose nanocrystals,glycerol,and essential oil of lemongrass were prepared and used to coat strawberries with a film formed directly on the surface of the coated fruit.The effects of the different edible coatings on refrigerated fruits in terms of weight loss,titratable acidity,total soluble solids,pH,and anthocyanin content was evaluated after 2 days,4 days,6 days,and 8 days of storage.Application of the edible coatings reduced the weight loss of the coated strawberries and the anthocyanin content.The total soluble solids content of or uncoated fruit increase more markedly than that of coated fruit.In contrast,pH was maintained for both coated and uncoated strawberries.The edible coatings were effective in minimizing of the weight loss,without worsening the physical chemistry attributes.The treatments T5 and T9 presented the best results.

Surface Chemical Modification of Cellulose Nanocrystals and Its Application in Biomaterials

Cellulose nanocrystals(CNCs) have been widely applied in biomaterials and show great biocompatibility and mechanical strength. In this review, the chemical reactions applied in CNC surface modification and their application in CNC based biomaterials are introduced. Furthermore, the conjugation of different functional molecules and nanostructures to the surface of CNCs are discussed, with focus on the binding modes, reaction conditions, and reaction mechanisms. With this introduction, we hope to provide a clear view of the strategies for surface modification of CNCs and their application in biomaterials, thus providing an overall picture of promising CNC-based biomaterials and their production.

Isolation of Thermally Stable Cellulose Nanocrystals from Spent Coffee Grounds via Phosphoric Acid Hydrolysis

As the world's population exponentially grows,so does the need for the production of food,with cereal production growing annually from an estimated 1.0 billion to 2.5 billion tons within the last few decades.This rapid growth in food production results in an ever increasing amount of agricultural wastes,of which already occupies nearly 50%of the total landfill area.For example,is the billions of dry tons of cellulose-containing spent coffee grounds disposed in landfills annually.This paper seeks to provide a method for isolating cellulose nanocrystals(CNCs)from spent coffee grounds,in order to recycle and utilize the cellulosic waste material which would otherwise have no applications.CNCs have already been shown to have vast applications in the polymer engineering field,mainly utilized for their high strength to weight ratio for reinforcement of polymer-based nanocomposites.A successful method of purifying and hydrolyzing the spent coffee grounds in order to isolate usable CNCs was established.The CNCs were then characterized using current techniques to determine important chemical and physical properties.A few crucial properties determined were aspect ratio of 12±3,crystallinity of 74.2%,surface charge density of(48.4±6.2)mM/kg cellulose,and the ability to successfully reinforce a polymer based nanocomposite.These characteristics compare well to other literature data and common commercial sources of CNCs.

Preparation of Dicarboxyl Cellulose Nanocrystals from Agricultural Wastes by Sequential Periodate-Chlorite Oxidation

Agricultural waste straw is the renewable resource with the highest annual yield in the world.In value-added applications of agricultural waste,dicarboxyl cellulose nanocrystals(DCCs)are prepared from rice,wheat,and corn straw by sequential periodate-chlorite oxidation.In this study,DCCs from rice,wheat,and corn straw were characterized by transmission electron microscopy(TEM),Fourier transform infrared spectrometer,X-ray diffractometer(XRD),and thermal gravimetric analysis(TGA).The carboxyl content of the DCCs was also investigated.XRD results show that the crystallinity index decreased after sequential periodate-chlorite oxidation;however,the cellulose I structure was maintained.TEM results show that rod-shaped DCCs with an average length and width of 287.0 nm and 9.9 nm,respectively,were successfully prepared by sequential periodate-chlorite oxidation.The carboxyl content of the DCCs was around 3.9 mmol/g,and not affected by the type of straw.Experiments to study the removal of copper ions in aqueous medium were performed with the prepared DCCs.The adsorption capacities of copper ions were 131,162,and 144 mg/g for DCCs prepared from rice,wheat,and corn straws,respectively.The results show that DCCs prepared from rice,wheat,and corn straws by sequential periodatechlorite oxidation have potential for the removal of copper ions from aqueous medium.

Green Modification of Cellulose Nanocrystals and Their Reinforcement in Nanocomposites of Polylactic Acid

Cellulose nanocrystals （CNCs） of rod-like shape were prepared from degreased cotton using sulfuric acid hydrolysis. The obtained CNC suspension was neutralized using a sodium hydroxide solution to remove the residual sulfuric acid and improve the thermal stability of the CNC particles. Then, poly（ethylene oxide） （PEO） was employed to modify the nanocrystals through entanglement and physical adsorption. The goal was to further improve the thermal stability and weaken the hydrophilicity of CNCs. Original and modifed CNCs were dosed into a polylactic acid （PLA） matrix to prepare nanocomposites using a hot compression process. Results of the thermogravimetric analysis showed that the initial thermal decomposition temperature of the modifed CNCs showed a 120℃ improvement compared to the original CNCs. That is, the thermal stability of the modified CNCs improved because of their shielding and wrapping by a PEO layer on their surface. Results from scanning electron microscopy and ultraviolet-visible spectrophotometry showed that the compatibility of the modifed CNCs with organic PLA improved, which was attributed to the compatibility of the PEO chains adsorbed on the surface of the CNCs. Finally, the results of tensile tests indicated a significant improvement in terms of breaking strength and elongation at the break point.

Cellulose Nanocrystals-based Chiroptical Materials

Chiroptical materials are widely used in photonic devices,enantioselective catalysis and bio-sensors.Cellulose-base chiroptical materials with multilength scale structural hierarchy and unique light manipulation ability found in nature provide inspiration for materials design.Cellulose nanocrystals(CNC)display twisted rod morphology and hierarchical chirality.Leveraging the evaporation-induced self-assembly of negatively charged CNC,a broad realm of CNC-based chiroptical materials featuring one-dimensional photonic bandgap and novel chiroptical properties have been developed,which are of scientific and technological significance.Here we presented a brief overview on CNC-based chiroptical materials by evaporation-induced self-assembly,showed energy and chirality transfer in a host-guest environment leading to photonic bandgap modulation of optoelectronic properties,outlined novel chiroptical phenomena and their underlying principles,and demonstrated the application potentials of the CNC-based chiroptical materials.

Injectable self-healing nanocellulose hydrogels crosslinked by aluminum:Cellulose nanocrystals vs.cellulose nanofibrils

With excellent biocompatibility and unique physiochemical properties,nanocelluloses including cellulose nanocrystals(CNCs)and cellulose nanofibrils(CNFs)are promising candidates for preparing biomedical hydrogels.CNCs and CNFs are different in morphology and surface charges.Herein,CNCs and two CNFs(CNFs-C,Carboxylated CNFs;CNFs-P,Phosphorylated CNFs)were synthesized and applied to fabricate hydrogels through metal crosslinking.Aluminum crosslinking was found to be the best choice for enhancing the strength.This study systematically compared the morphologies,storage modulus,loss factor,continuous shear ramp,self-healing,swelling,in vitro degradation and injectable properties of the fabricated hydrogels,Further,a radar chart is summarized as guidelines to direct the rational selection to meet the specific requirements of further biomedical applications.At the same nanocellulose concentration and after Al^(3+)crosslinking,CNCs hydrogels had strong water holding capacity twice as much as that of CNFs hydrogels.While CNFs hydrogels showed higher hardness and stronger resistance to degradation than that of CNCs.These results provide detailed insights into nanocellulose hydrogels,making it possible to use these guidelines to select hydrogels for desired performance.

The Application of Cellulose Nanocrystals Modified with Succinic Anhydride under the Microwave Irradiation for Preparation of Polylactic Acid Nanocomposites

The aim of this work was to use cellulose nanocrystals that were obtained by hydrolysis in phosphoric acid solution and further modified with succinic anhydride in the microwave field for PLA reinforcement.A series of allbionanocomposites containing unmodified and surface modified cellulose nanocrystals with CNC content in the range of 1–3%_(w.t.) were obtained by melt blending and tested by XRD,SEM,DSC and DMA to investigate the effect of surface esterification of CNCs on the structure,morphology,dynamic mechanical properties of bionanocomposites,as well as phase transitions of PLA in the presence of cellulosic nanofiller.DMA investigations showed the highest increase of storage modulus by ca.7%(335 MPa at 25℃)in the glassy state of PLA for 2%_(w.t.)of unmodified CNC.Though,addition of 2%_(w.t.)of succinylated CNCs caused the highest increase of the onset of glass transition temperature(by 6.2℃)thus widening the temperature range of biocomposite application.The increase of glass transition temperature indicates the strongest interfacial interactions due to improved miscibility of surface modified nanocrystals and thus good dispersion of additive in PLA matrix providing high interface.

Synergistic effects of chloride anions and carboxylated cellulose nanocrystals on the assembly of thick three-dimensional high-performance polypyrrole-based electrodes

Porous three-dimensional (3D) structures generally improve the performance of electrodes by increasing their active surface area and the diffusion speed of electrolyte ions during charging/discharging.Threedimensional polypyrrole (PPy) based films were created by electrodepositing PPy in the presence of varying amounts of chloride anions (Cl^(-)) and polyanionic ribbonlike nanoparticles (carboxylated cellulose nanocrystals (CNC-COO-)) as scaffold material.The assembly mechanism of the 3D PPy electrodes combines the effect of different nucleation and growth mechanisms during electropolymerization and deposition of the formed PPy with CNC-COO-and with Cl^(-).The highest area capacitance of these electrode materials was 1.39 F cm^(-2)(150.2 F g^(-1)) at a current density of 1 m A cm^(-2)(0.1 A g^(-1)).More importantly,at a high current density of 20 m A cm^(-2)(2.2 A g^(-1)),the thick (ca.130μm),3D,and high mass loading(9.2 mg cm^(-2)) Cl^(-):CNC-COO-/PPy films exhibited an excellent areal capacitance of 0.85 F cm^(-2)(70.8 F g^(-1)),increasing about 16%over CNC-COO-/PPy films prepared without Cl^(-)present during electrodeposition.In addition,an aqueous Cl^(-):CNC-COO-/PPy (with Cl^(-):CNC-COO-=2.0) symmetric supercapacitor had an outstanding energy density of 41.15μWh cm^(-2)(4.46 Wh kg^(-1)) and excellent cycling stability,while even improving on its original areal capacitance (to 111.2%of its original capacitance) after cycling3000 cycles at 8 m A cm^(-2),indicating their potential in energy storage devices.

Rheological and DSC Studies on the Interaction between κ-Carrageenan and Cellulose Nanocrystals (CNC)

Rheometer and differential scanning calorimetry （DSC） have been used to probe the mechanism of gelation in gels formed by mixture of k-carrageenan and cellulose nanocrystals （CNC）. The results indicated that an association occurred between CNC chains and aggregated k-carrageenan helices.

Effects of cellulose nanocrystals on the acid resistance of cementitious composites

Acid mine drainage presents an important threat to cementitious structures.This study is aimed at investigating the effect of cellulose nanocrystals(CNCs)on the acid resistance of cementitious composites.CNCs were added to mortar mixtures as additives at cement volume ratios of 0.2vol%,0.4vol%,1.0vol%,and 1.5vol%.After 28 d of standard curing,the samples were immersed in a sulfuric acid with a pH value of 2 for 75 d.The unconfined compressive strength(UCS)test,the density,water absorption,void volume test,and thermogravimetric analysis were carried out to investigate the properties of CNC mixtures before sulfuric acid immersion.It was found that the addition of CNC reduced the volume of permeable voids and increased the hydration degree and mechanical strength of the samples.Changes in mass and length were monitored during immersion to evaluate the acid resistance of mixtures.The mixture with 0.4vol%CNC showed a reduced mass change and length change indicating its improved acid resistance.

Poly(Butylene Adipate-Co-Terephthalate)and Poly(ε-Caprolactone)and Their Bionanocomposites with Cellulose Nanocrystals:Thermo-Mechanical Properties and Cell Viability Study

Although nanocomposites have recently attracted special interest in the tissue engineering area,due to their potential to reinforce scaffolds for hard tissues applications,a number of variables must be set prior to any clinical application.This manuscript addresses the evaluation of thermo-mechanical properties and of cell proliferation of cellulose nanocrystals(CNC),poly(butylene adipate-co-terephthalate)(PBAT),poly(ε-caprolactone)(PCL)films and their bionanocomposites with 2 wt% of CNC obtained by casting technique.Cellulose nanocrystals extracted from Balsa wood by acid hydrolysis were used as a reinforcing phase in PBAT and PCL matrix films.The films and pure CNC at different concentrations were cultured with osteoblasts MG-63 and the cell proliferation was assessed by AlamarBlue?assay.The thermal-mechanical properties of the films were evaluated by dynamic-mechanical thermal analysis(DMTA).It was found by DMTA that the CNC acted as reinforcing agent.The addition of CNCs in the PBAT and PCL matrices induced higher storage moduli due to the reinforcement effects of CNCs.The cell viability results showed that neat CNC favored osteoblast proliferation and both PBAT and PCL films incorporated with CNC were biocompatible and supported cell proliferation along time.The nature of the polymeric matrix or the presence of CNC practically did not affect the cell proliferation,confirming they have no in vitro toxicity.Such features make cellulose nanocrystals a suitable candidate for the reinforcement of biodegradable scaffolds for tissue engineering and biomedical applications.

Adsorption Behavior of Reducing End-Modified Cellulose Nanocrystals:A Kinetic Study Using Quartz Crystal Microbalance

In this work,we studied the adsorption of modified cellulose nanocrystals onto solid surfaces by quartz crystal microbalance with dissipation monitoring(QCM-D).Cellulose nanocrystals obtained from tunicate(CNC)were modified at reducing end by amidation reactions.Two different functionalities were investigated:a polyamine dendrimer(CNC-NH_(2)),which interacts with gold surface by the amine groups;and a biotin moiety(CNC-Biot),which has a strong affinity for the protein streptavidin(SAV).QCM-D results revealed different adsorption behaviors between modified and unmodified CNCs.Hence,unmodified CNCs covered almost all the surface forming a rigid and flat layer whereas reducing end modified CNCs remained rather upright forming a hydrated and viscoelastic layer with lower surface coverage.The analysis of adsorption kinetics allowed the calculation of an apparent collision rate factor,which resulted 10-fold higher for unmodified CNCs compared to reducing end modified CNCs,therefore,demonstrating the different adsorption behavior.

Composite Biomaterials Based on Poly(L-Lactic Acid)and Functionalized Cellulose Nanocrystals

The biocomposite films were prepared from poly(L-lactic acid)and cellulose nanocrystals.To improve interfacial compatibility of hydrophilic cellulose nanocrystals with hydrophobic matrix polymer as well as to provide the osteoconductive properties,cellulose was functionalized with poly(glutamic acid).The modified cellulose nanocrystals were better distributed and less aggregated within the matrix,which was testified by scanning electron,optical and polarized light microscopy.According to mechanical tests,composites filled with nanocrystals modified with PGlu demonstrated higher values of Young’s modulus,elongation at break and tensile strength.Incubation of composite materials in model buffer solutions for 30 weeks followed with staining of Ca^(2+)deposits with Alizarin Red S assay testified better mineralization of materials containing PGlu-modified cellulose nanocrystals as filler.As the result of in vivo experiment,the developed composite materials showed less level of inflammation in comparison with pure polymer matrix and composites filled with non-functionalized cellulose nanocrystals.

The Application of Cellulose Nanocrystals in Pickering Emulsion as the Particle Stabilizer

Pickering emulsions stabilized by solid particles have attracted considerable interest by the food,pharmaceutical,and cosmetic industries.Cellulose nanocrystals(CNCs),with their high aspect ratio,renewability,degradability and biocompatibility,proved to be excellent Pickering stabilizers.This paper will initially review the purification and extraction methods used for targeted cellulose nanocrystals.This will be followed by a discussion of factors influencing the stability of Pickering emulsions containing cellulose nanocrystals.The applications of Pickering emulsions stabilized with cellulose naocrystals will be briefly discussed as well as research ideas for their future uses.

Polycaprolactone (PCL) Chains Grafting on the Surface of Cellulose Nanocrystals (CNCs) during <i>In Situ</i>Polymerization of <i>ε</i>-Caprolactone at Room Temperature

This work aimed at investigating the feasibility of surface modification of cellulose nanocrystals (CNCs) using in situ ring opening polymerization of ε-caprolactone (ε-CL) at room temperature. Residues of flax and milkweed (Asclepias syriaca) stem fibers were used as a source of cellulose to obtain and isolate CNCs. The cationic ring opening polymerization (CROP) of the monomer ε-CL was used to covalently graft polycaprolactone (PCL) chains at the CNCs surface. Silver hexafluoroantimonate (AgSbF6) was used in combination with the extracted CNCs to initiate, at room temperature, the polymerization and the grafting reactions with no other stimulus. Fourier-Transform InfraRed (FTIR), X-ray Photoelectron Spectrometry (XPS), UV/visible absorption and Gel Permeation Chromatography (GPC) analyses evidenced the presence of PCL chains covalently grafted at CNCs surface, the formation of Ag(0) particles as well as low or moderate molecular weight free PCL chains.