Surface Of Cellulose Nanowhiskers Research Articles

A Flexible, Low-Cost, Disposable Non-Enzymatic Electrochemical Sensor Based on MnO2/Cellulose Nanostructure

In this investigation, a new class of polysaccharide (cellulose nanowhiskers ) in the presence of manganese oxide nanoparticles (MnO2 NPs) to produce hybrid materials was synthesized and used as a new sensor platform with high and fast electrochemical responses. A simple method of synthesis for producing different cellulosic nanostructures has been evaluated and characterized by Fourier-transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), scanning electron microscope (SEM),cyclic voltammogram (CV) and electrochemical impedance spectra (EIS). The FTIR analysis data approved the formation of cellulose and MnO2 nanostructures. The uniform distribution of MnO2 nanostructure over the cellulose nanowhiskers surface has been approved by using SEM. In addition, From CV and EIS characterization MnO2/Cellulose hybrid materials have electrocatalytic properties and promising applications in biosensors and non-enzymatic sensors fields. The MnO2/cellulose non-enzymatic sensor have been used for hydrogen peroxide choronoamperometric detection with high sensitivity 0.70 μA μM−1, a linear concentration range from 0.2 − 400 μM, lower of detection limit (LOD) of 0.04 μM (S/N = 3) and R2 of 0.98. The sensor was used for hydrogen peroxide detection in real samples with a high percentage of recovery from 93 to 110 %.

Hybrid materials for bone tissue engineering from biomimetic growth of hydroxiapatite on cellulose nanowhiskers

Cellulose nanowhiskers (CNWs) with different surface composition were used to generate the biomimetic growth hydroxyapatite (HAp). Hybrids materials primarily consist of CNWs with HAp content below 24%. CNWs were produced by different inorganic acid hydrolyses to generate cellulose particles with surface groups to induce HAp mineralization. In the present study, we evaluate the use of CNWs prepared from hydrochloric acid, sulfuric acid and phosphoric acid. HAp growth was obtained from the biomimetic method using a simulated body fluid concentration of 1.5M (SBF). The sulfonate and phosphonate groups on the CNW surface have a direct impact on the nucleation and growth of HAp. HAp/CNW were also compared with the physical mixture method using HAp nanoparticles prepared by chemical precipitation. The bioactivity and biocompatibility of the hybrid materials were assessed by cell viability studies using fibroblast cells (L929). The materials obtained from the biomimetic method have superior biocompatibility/bioactivity compared to the material synthesized by the wet chemical precipitation method with an incubation period of 24h.

Use of surfactants in cellulose nanowhisker/epoxy nanocomposites: effect on filler dispersion and system properties

Cellulose nanowhiskers (CNWs) prepared via TEMPO mediated oxidation are used as biodegradable filler in an epoxy matrix. Since CNWs are hydrophilic and epoxy is hydrophobic, amphiphilic block copolymer surfactants are employed to improve the interactions between the filler and the matrix. The surfactants used are Pluronics, a family of triblock copolymers containing two poly(ethylene oxide) blocks and one poly(propylene oxide) block. In this study, Pluronic L61 and L121 with molecular weight of 2000 and 4400 g/mol and hydrophilic to lipophilic balance of 3 and 1 respectively, are used and their effect on the dispersion of CNWs in epoxy is discussed. The hydrophilic tails of Pluronics interact with the hydroxyl and carboxylic groups on the CNW surface and then these surfactant-treated CNWs are directly incorporated into epoxy by high speed mixing. The dispersion state of the surfactant-treated CNWs in epoxy is assessed by rheological measurements and the mechanical properties of the resulting composites are characterized by tensile test and dynamic mechanical thermal analysis. The Pluronic L61 treated CNW/epoxy composites show the highest storage modulus at high temperatures (about 77 % increases) indicative of improved interfacial interactions between the CNWs and the epoxy matrix. Also, an increase of around 10 °C in the glass–rubbery transition temperature of the L61 treated CNW/epoxy composite leads to potential application at higher service temperatures.

Dendronization of cellulose nanowhisker with cationic hyperbranched dendritic polyamidoamine.

Polyamidoamine (PAMAM) dendrimers with active amino group up to the third generation were grafted onto the surface of cellulose nanocrystals (CNCs) by a divergent method. Cellulose nanowhiskers (CNW) are gaining interest as a "green" nanomaterial with exceptional chemical and mechanical properties for high-performance nanocomposite materials. Cellulose nanowhiskers are usually isolated from cotton by sulfuric acid hydrolysis and hydrochloric acid hydrolysis. The grafting of PAMAM dendrimer on CNW surface was monitored using FTIR, (1)H NMR, DLS and AFM. The results of FTIR and (1)H NMR confirmed the formation of PAMAM on the CNW. AFM images indicated the PAMAM synthesis on CNW through the nano-scale structures of macromolecules. The Zeta-potential value of polymer was found to be around +25 mV, and according to the collected data, the effective diameter of the CNW-g-PAMAM particles measured through DLS technique was found to be 73 nm.

Effect of cellulose nanowhiskers on surface morphology, mechanical properties, and cell adhesion of melt-drawn polylactic Acid fibers.

Polylactic acid (PLA) fibers were produced with an average diameter of 11.2 (± 0.9) μm via a melt-drawing process. The surface of the PLA fibers was coated with blends of cellulose nanowhiskers (CNWs) (65 to 95 wt %) and polyvinyl acetate (PVAc). The CNWs bound to the smooth PLA fiber surface imparted roughness, with the degree of roughness depending on the coating blend used. The fiber tensile modulus increased 45% to 7 GPa after coating with 75 wt % CNWs compared with the uncoated PLA fibers, and a significant increase in the fiber moisture absorption properties at different humidity levels was also determined. Cytocompatibility studies using NIH-3T3 mouse fibroblast cells cultured onto CNWs-coated PLA surface revealed improved cell adhesion compared with the PLA control, making this CNW surface treatment applicable for biomedical and tissue engineering applications. Initial studies also showed complete cell coverage within 2 days.

The transparency and mechanical properties of cellulose acetate nanocomposites using cellulose nanowhiskers as fillers

Cellulose nanowhiskers (CNWs) were chemically modified by acetylating to obtain acetylated cellulose nanowhiskers (ACNWs) which could be well dispersed in acetone. The chemical modification was limited only on the surface of CNWs which was confirmed by transmission electron microscopy (TEM) and X-ray diffraction (XRD). Surface substitution degree of ACNWs was evaluated to be 0.45 through X-ray photoelectron spectroscopy (XPS). Fully bioresource-based nanocomposite films were manufactured by incorporation of ACNWs into cellulose acetate (CA) using a casting/evaporation technique. Scanning electron microscope (SEM) demonstrated that ACNWs dispersed well in the CA matrix, which resulted in high transparency of all CA nanocomposites. The tensile strength, Young’s modulus and strain at break of all CA nanocomposites exhibited simultaneous increase in comparison with neat CA matrix. At the content of 4.5 wt% ACNWs, the tensile strength, Young’s modulus and strain at break of the CA nanocomposite film were increased by 9, 39, and 44 % respectively.

Polyester-Grafted Cellulose Nanowhiskers: A New Approach for Tuning the Microstructure of Immiscible Polyester Blends

Cellulose nanowhiskers (CNW), extracted from ramie fibers by sulfuric acid hydrolysis, were used as substrates to compatibilize binary polyester blends containing 50/50 (w/w) polycaprolactone (PCL) and polylactide (PLA). To tailor their interfacial energy and fine-tune their adhesion with the components of the blend, CNW were subjected to different surface polyester grafting by the means of ring-opening polymerization. PCL and PLA homopolyesters as well as P(CL-b-LA) diblock copolymers were successfully grafted on the surface of CNW and the resulting substrates were loaded into the PCL/PLA blend by melt-blending. Morphological and rheological analyses were conducted in order to evaluate the ability of these nanoparticles to enhance the compatibility of PCL/PLA blends. Our results showed that unmodified CNW as well as (co)polyester-grafted CNW improved, at different levels, the compatibility of PCL/PLA blends by preventing from coalescence the dispersed domains. (co)polyester-grafted CNW also enhance the mechanical properties of the blend, which can be explained by the formation of cocontinuous phase morphology at the interface. Our findings suggest that (co)polyester-grafted CNW, especially CNW-g-P(CL-b-LA) diblock copolymers, can serve as a suitable nanofiller to tune the compatibility of PCL/PLA blends and their related microstructures.

Surface-modification of cellulose nanowhiskers and their use as nanoreinforcers into polylactide: A sustainably-integrated approach

In this study, bionanocomposites based on renewable cellulose nanowhiskers (CNWs) as nanofillers and renewable poly(l-lactide) (PLA) as polymeric matrix were successfully and straightforwardly prepared using melt-extrusion technique. Due to the affinity difference between hydrophobic PLA and hydrophilic CNWs, the surface of CNWs was directly modified in aqueous suspension (pH=5.4 – citrate buffer) at ambient temperature in the presence of functional trialkoxysilanes bearing various organic moieties (alkyl, amino, and (meth)acryloxy). The surface-functionalization of CNWs was first investigated using methacryloxy-based trialkoxysilane as model. The influence of parameters such as the amount of silane agents and the post-treatment conditions were optimized on the surface-modification of methacryloxy-modified CNWs. FT-IR, TEM, WAXS and XPS analyses provided further evidences about the efficiency of the surface-modifications of CNWs. In a subsequent step, the chemically modified CNWs were successfully incorporated into PLA by melt-extrusion in the absence of solvent, without any alterations of their nanostructure after melt-processing. The thermal/mechanical properties of the resulting bionanocomposites were determined and shown to be enhanced when silanized CNWs were used as nanofillers.

From Interfacial Ring-Opening Polymerization to Melt Processing of Cellulose Nanowhisker-Filled Polylactide-Based Nanocomposites

In the present work, cellulose nanowhiskers (CNWs), extracted from ramie fibers, were incorporated in polylactide (PLA)-based composites. Prior to the blending, PLA chains were chemically grafted on the surface of CNW to enhance the compatibilization between CNW and the hydrophobic polyester matrix. Ring-opening polymerization of l-lactide was initiated from the hydroxyl groups available at the CNW surface to yield CNW-g-PLA nanohybrids. PLA-based nanocomposites were prepared by melt blending to ensure a green concept of the study thereby limiting the use of organic solvents. The influence of PLA-grafted cellulose nanoparticles on the mechanical and thermal properties of the ensuing nanocomposites was deeply investigated. The thermal behavior and mechanical properties of the nanocomposites were determined using differential scanning calorimetry (DSC) and dynamical mechanical and thermal analysis (DMTA), respectively. It was clearly evidenced that the chemical grafting of CNW enhances their compatibility with the polymeric matrix and thus improves the final properties of the nanocomposites. Large modification of the crystalline properties such as the crystallization half-time was evidenced according to the nature of the PLA matrix and the content of nanofillers.

Preparation and characterization of cellulose nanowhiskers from cotton fibres by controlled microbial hydrolysis

The cellulolytic fungus Trichoderma reesei was used to prepare cellulose nanowhiskers (CNW) by controlled hydrolysis of microcrystalline cellulose (MCC). The penetration of fungus into the ordered regions of MCC resulted in reduction (10%) of its crystallinity. The zeta potential of fungal hydrolyzed CNW was similar to that of native MCC while that of CNW prepared by acid hydrolysis was five times higher due to its surface sulfation. Also, fungal hydrolyzed CNW resulted in monodomain structure under polarized light microscopy (PLM) while it was polydomain for that of acid hydrolyzed CNW. Atomic force microscopic (AFM) analysis confirmed the preferential orientation (anisotropy) of CNW on drying. Preparation of CNW by concentrated sulfuric acid hydrolysis process is energy intensive, environmentally hazardous and the surface of CNW is chemically modified (sulfated). But fungal hydrolysis resulted in CNW without any surface modification and such nanostructures show promise for applications in eco-friendly composites and pharmaceuticals.

Thermal and mechanical properties of poly(3-hydroxybutyrate-co-3-hydroxyvalerate)/cellulose nanowhiskers composites

Bacterial polyester poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) was reinforced with cellulose nanowhiskers (CNW) in 1–5wt.% concentrations using a solvent casting method. The CNW was prepared from microcrystalline cellulose (MCC) using sulfuric acid hydrolysis. The influence of CNW on the PHBV crystallization, thermal, dynamic mechanical and mechanical properties were evaluated using polarized optical microscope (POM), differential scanning calorimeter (DSC), dynamic mechanical analysis (DMA), tensile and bulge tests, respectively. POM test results demonstrated that CNW was an effective PHBV nucleation agent. Tensile strength, Young’s modulus and toughness of PHBV increased with the increasing concentration of CNW. DMA results showed an increased tan δ peak temperature and broadened transition peak, indicating restrained PHBV molecular mobility in the vicinity of the CNW surface. Storage modulus of the PHBV also increased with the addition of CNW, especially at the temperatures higher than the PHBV glass transition temperature. These results indicated that the CNW could substantially increase the mechanical properties of PHBV and this increase could be attributed to the strong interactions between these two phases.

Review: current international research into cellulose nanofibres and nanocomposites

This paper provides an overview of recent progress made in the area of cellulose nanofibre-based nanocomposites. An introduction into the methods used to isolate cellulose nanofibres (nanowhiskers, nanofibrils) is given, with details of their structure. Following this, the article is split into sections dealing with processing and characterisation of cellulose nanocomposites and new developments in the area, with particular emphasis on applications. The types of cellulose nanofibres covered are those extracted from plants by acid hydrolysis (nanowhiskers), mechanical treatment and those that occur naturally (tunicate nanowhiskers) or under culturing conditions (bacterial cellulose nanofibrils). Research highlighted in the article are the use of cellulose nanowhiskers for shape memory nanocomposites, analysis of the interfacial properties of cellulose nanowhisker and nanofibril-based composites using Raman spectroscopy, switchable interfaces that mimic sea cucumbers, polymerisation from the surface of cellulose nanowhiskers by atom transfer radical polymerisation and ring opening polymerisation, and methods to analyse the dispersion of nanowhiskers. The applications and new advances covered in this review are the use of cellulose nanofibres to reinforce adhesives, to make optically transparent paper for electronic displays, to create DNA-hybrid materials, to generate hierarchical composites and for use in foams, aerogels and starch nanocomposites and the use of all-cellulose nanocomposites for enhanced coupling between matrix and fibre. A comprehensive coverage of the literature is given and some suggestions on where the field is likely to advance in the future are discussed.