Spruce galactoglucomannans (GGM) and konjac glucomannan (KGM) were mixed with cellulose nanowhiskers (CNW) to form composite
films. Remarkable effects of CNW on the appearance of the films were detected when viewed with regular and polarizing optical
microscopes and with a scanning electron microscope. Addition of CNW to KGM-based films induced the formation of fiberlike
structures with lengths of several millimeters. In GGM-based films, rodlike structures with lengths of several tens of micrometers
were formed. The degree of crystallinity of mannan in the plasticized KGM-based films increased slightly when CNW were added,
from 25 to 30%. The tensile strength of the KGM-based films not containing glycerol increased with increasing CNW content
from 57 to 74 MPa, but that of glycerol-plasticized KGM and GGM films was not affected. Interestingly, the notable differences
in the film structure did not appear to be related to the thermal properties of the films. 相似文献
Cellulose - The self-assembly of cellulose nanowhiskers (CNWs) in confined geometries provides a powerful method for the fabrication of novel structures. Herein, ordered honeycomb microporous films... 相似文献
Bionanocomposites with improved properties based on two microbial polysaccharides, pullulan and bacterial cellulose, were
prepared and characterized. The novel materials were obtained through a simple green approach by casting water-based suspensions
of pullulan and bacterial cellulose and characterized by TGA, RDX, tensile assays, SEM and AFM. The effect of the addition
of glycerol, as a plasticizer, on the properties of the materials was also evaluated. All bionanocomposites showed considerable
improvement in thermal stability and mechanical properties, compared to the unfilled pullulan films, evidenced by the significant
increase in the degradation temperature (up to 40 °C) and on both Young’s modulus and tensile strength (increments of up to
100 and 50%, for films without glycerol and up to 8,000 and 7,000% for those plasticized with glycerol). Moreover, these bionanocomposite
films are highly translucent and could be labelled as sustainable materials since they were prepared entirely from renewable
resources and could find applications in areas as organic electronics, dry food packaging and in the biomedical field. 相似文献
In this study, the detailed characterisation of silver (Ag) nanoparticles/polymer nanocomposite chemical structure and morphology of grating has been carried out. Scanning electron microscopy measurements show spherical shape of Ag nanoparticles (40–80 nm in diameter) prepared in chloroform by reduction of silver nitrate. In the positive photoresist based on 2-diazo-2H-naphthalen-1-one (DNQ)–novolac, Ag nanoparticles were deposited from organic colloidal solution. The content of nanoparticles in the polymer matrix was varied by increasing the concentration of Ag colloidal solution. Grating was formed by contact lithography. The quantification of Ag nanoparticles and chemical analysis of Ag/DNQ-novolac-based nanocomposite was performed by means of energy dispersive X-ray analyzer and SEM/EDS. In order to study the effect of Ag nanoparticles on the DNQ-novolac-based nanocomposite structure, investigations with Fourier transform infrared spectroscopy were conducted. Ag nanoparticles cause changes associated with substituent-sensitive out-of-plane C–H bending vibrations of aromatic ring. Ag/DNQ-novolac-based nanocomposite film surface morphology and grating topography imaging were performed using atomic force microscopy. Added Ag nanoparticles change the geometrical parameters of the gratings. The split of corrugations was achieved in Ag/DNQ-novolac-patterned films. Their morphology can be tailored by altering the content of Ag nanoparticles. 相似文献
The mechanical properties, morphologies, and gas barriers of hybrid films of cellulose with two different organoclays are
compared. Dodecyltriphenyl-phosphonium-mica (C12PPh-mica) and hexadecyl-mica (C16-mica) were used as reinforcing fillers in the fabrication of the cellulose hybrid films. The cellulose hybrid films were
synthesized from N-methyl-morpholine-N-oxide (NMMO) solutions with the two organo-micas, and solvent-cast at room temperature under vacuum, yielding 15–20 μm thick
films of cellulose hybrids with various clay contents. We found that the addition of only a small amount of organoclay is
sufficient to improve the mechanical properties and gas barriers of the cellulose hybrid films. Even polymers with low organoclay
contents (1–7 wt %) were found to exhibit much higher strength and modulus values than pure cellulose. The addition of C12PPh-mica was more effective than that of C16-mica with regards to the initial tensile modulus, whereas the addition of C16-mica was more effective than that of C12PPh-mica with regards to the gas barrier of the cellulose matrix. The intercalations of the polymer chains in the clays were
examined with wide-angle X-ray diffraction (XRD) and electron microscopy (SEM and TEM). 相似文献
Cellulosic nanocomposite membranes were prepared by incorporation of cellulose nanocrystals (CNCs) into a hydroxypropyl cellulose (HPC) matrix using a mixing/evaporation technique. CNCs were obtained from filter paper using the sulfuric acid hydrolysis method with the aid of ultrasonication. The relationship between the microstructure and mechanical properties of the CNCs/HPC nanocomposite membranes was studied. Scanning electron microscopy showed that the CNCs were well dispersed in the HPC matrix, and the fracture surface demonstrated a fibrous characteristic. With increasing CNCs content, the tensile strength and Young’s modulus of the CNCs/HPC nanocomposite membranes gradually increased. At 5 wt% content of CNCs, the strength was increased by 525 % and the Young’s modulus by 124 % compared with pure HPC membrane. Moreover, the effect of the phase change of HPC on the mechanical properties of the CNCs5wt%/HPC nanocomposite membranes and the corresponding mechanism were also studied. 相似文献
This study introduces an effective route to fabricate chitosan (CS)-based film. The films were prepared through cross-linking reaction between CS and hydroxyethyl cellulose (HEC) using epichlorohydrin (ECH) as the cross-linker and simultaneously in-situ loading with CuO nanoparticles. FT-IR and loading efficiency results indicated the occurrence of inter- and intra-molecular cross-linking reaction between CS and HEC. XRD and EDS analyses showed that the CuO nanoparticles were evenly deposited onto CS film matrixes. SEM characterization showed that the films were of compact, dense and uniform cross morphologies, as well as obvious voids. The films also exhibited desired swelling ratio and water vapor permeability. The enhanced tensile strength was obtained with a maximum value of 77.02?±?3.26 MPa, while the stretch-ability slightly decreased. The thermal stability of the films decreased after cross-linking with HEC. The antibacterial ability of the films was generally improved with the increase of HEC and ECH contents.
Graphical abstract
Preparation and properties of epichlorohydrin-cross-linked chitosan/hydroxyethyl cellulose based CuO nanocomposite films
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. 相似文献
Recyclable and transparent nanocomposite films based on bacterial cellulose (BC) and hemiaminal dynamic covalent network polymer (HDCN) have been synthesized by in situ polymerization of 4,4′-diaminodiphenyl ether (ODA) with paraformaldehyde. Transparency and structural and mechanical properties of such nanocomposite films are investigated. It was found that BC/HDCN nanocomposite films exhibits a high optical transparency (86 % at 550 nm). Scanning electron microscopy reveals excellent compatibility of the reinforcement of BC nanofibers and HDCN matrix, which leads to the improvement of 20 and 200 % in tensile strength and storage modulus, respectively, as compared to neat HDCN films. BC hydrogels are readily recoverable from nanocomposite films by the sulphuric acid treatment and ODA monomer is deposited and also recycled. 相似文献
Nanocomposite hybrid films containing silicon and titanium compounds in the polymer matrix are prepared through the sol-gel method via the hydrolytic polycondensation of Si and Ti alkoxides (tetraethoxysilane and titanium tetrabutoxide) in the THF solution of a hydrophobic polymer, ethyl cellulose. Their structure and properties are studied with the use of a complex of physicochemical methods. During the hydrolysis of tetraethoxysilane and the subsequent polycondensation of the reaction products, silicon atoms are incorporated into the polymer and form -O-Si-O-bonds involving hydroxyl groups of ethyl cellulose. In the sol-gel method, titanium alkoxide yields nanosized particles of titanium dioxide that play the role of fillers in the polymer matrix. Titanium-containing films show solubility in THF and, after prolonged contact with the solvent, precipitate titanium dioxide from the solution. Hybrid films containing silicon are insoluble owing to the formation of a chemical network between polymer molecules and Si-OH groups of the products of hydrolysis of silicon alkoxide, as confirmed by the IR data. It is shown that the amounts and types of alkoxides and the diameters of the structures formed in the polymer matrix via the sol-gel procedure affect the hydrophilicity levels of ethyl cellulose hybrid films and their abilities to swell in water and aqueous solutions of organic dyes (brilliant blue and methylene blue). Ethyl cellulose hybrid films are hydrophilic, and they facilitate the removal of dye molecules from aqueous solutions. The best properties are featured by the films containing nanosized particles of titanium dioxide in the polymer matrix. 相似文献
Bio-based continuous fibers were prepared by melt spinning cellulose acetate butyrate (CAB), cellulose nanocrystals (CNC) and triethyl citrate. A CNC organo-gel dispersion technique was used and the prepared materials (2 and 10 wt% CNC) were melt spun using a twin-screw micro-compounder and drawn to a ratio of 1.5. The microscopy studies showed that the addition of CNC in CAB resulted in defect-free and smooth fiber surfaces. An addition of 10 wt% CNC enhanced the storage modulus and increased the tensile strength and Young’s modulus. Fiber drawing improved the mechanical properties further. In addition, a micromechanical model of the composite material was used to estimate the stiffness and showed that theoretical values were exceeded for the lower concentration of CNC but not reached for the higher concentration. In conclusion, this dispersion technique combined with melt spinning can be used to produce all-cellulose nanocomposites fibers and that both the increase in CNC volume fraction and the fiber drawing increased the mechanical performance. 相似文献
Cellulose nanowhiskers (CNWs) were chemically modified with dodecenyl succinic anhydride to obtain hydrophobic CNWs called DCNWs. Surface modification was confirmed by infrared spectroscopy, transmission electron microscopy, and X-ray diffraction. The surface substitution degree determined by X-ray photoelectron spectroscopy was 0.30. Nanocomposites were prepared by incorporating different amounts of DCNWs pre-dispersed in a small amount of acetone into an epoxy matrix. Scanning electron microscope demonstrated that DCNWs dispersed well in the epoxy matrix. A strong interaction was proved between the DCNWs and epoxy matrix, as results of which the nanocomposites exhibited an obvious increase in Tg by about 30 °C, simultaneous increases in tensile strength, Young’s modulus, and strain at break; and an improvement in the hydrothermal properties. Compared with the neat epoxy, the nanocomposite containing 3.5 wt% of DCNWs exhibited an increase in tensile strength by 82 %, Young’s modulus by 21 %, and a strain at break by 198 %. 相似文献
Nanocrystalline cellulose (NCC) is a promising nanofiller for reinforcing chitosan (CTS) film. The flocculation of the NCC suspension in acidic CTS solution is the key problem that makes many properties such as the tensile strength bad. A derivative of nanocellulose, namely cationic dialdehyde cellulose (CDAC), is synthesized in the current study to avoid the flocculation. A CDAC suspension is prepared in a successive oxidation-reductive amination process of NCC. The oxidation of NCC led to smaller rod-like nanocrystals with a reduced crystallinity. The suspension with 1.0% CDAC is well mixed with 1.0% CTS solution. Besides, the tensile strength and anti-swelling properties of CDAC-filled CTS nanocomposite films are improved because of the uniform distribution of CDAC in the CTS matrix plus the intermolecular chemical cross-linking between CDAC and CTS. The tensile strength of CTS-based nanocomposite film with 12% CDAC is about 58.4% higher than that of the pure CTS film. 相似文献
Indiscriminate adsorption of nanoparticles (NPs) significantly complicates the preparation of mesoscale NP patterns considered as enabling technology for many devices and processes. Instead of selected chemical functionalization of the substrate surface prior to the assembly of nanocolloids, the required optical properties - in our case, high quantum yield luminescence - are imparted to the layer-by-layer assembled films by spatially selected photoactivation. The films are made by sequential adsorption of a positively charged polyelectrolyte and a negatively charged CdSe/CdS aqueous dispersion with an initial quantum yield of 0.5-2%. The photoactivation process takes place in the presence of oxygen and may be accompanied by photoetching. A 50-500-fold increase in the luminescence intensity of CdSe/CdS citrate-stabilized particles (quantum yield 25-45%) after visible light illumination provides excellent pattern contrast. Micron scale luminescence patterns were produced from NPs of various CdSe core diameters with red, yellow, and green emission. It was also demonstrated that different emission colors such as orange and green can be combined in one image by taking advantage of spatially selective photoetching. The presented optical patterning technique significantly simplifies the preparation of luminescence patterns as compared to conventional methods. The high signal-to-noise ratio associated with it is essential for optical devices, information processing, and biophotonics. The most immediate use of this approach is expected in cryptography and cell monitoring. 相似文献