The adsorption of cellulose acetate (CA), cellulose acetate propionate (CAP) and cellulose acetate butyrate (CAB) from solutions
prepared in acetone onto silicon wafers led to ultrathin films, which were characterized by ellipsometry, atomic force microscopy
(AFM) and contact angle measurements. The polysaccharides films were characterized in the air just after their formation and
after annealing at temperatures higher than their glass transition temperature or melt temperature. The films thickness close
to 2 nm and surface roughness did not vary significantly upon annealing. AFM images revealed the presence of small clumps
dispersed on a homogeneous layer, which covered completely the Si wafers. Such topographic details were also observed after
annealing. However, upon annealing the films surfaces changed from hydrophilic to hydrophobic, evidencing molecular re-orientation
at the solid–air interface. The adhesion of bovine serum albumin (BSA) and lipase onto the cellulose esters films was quantified
in order to evaluate the possibility of applying such films as selective support for biomolecules. 相似文献
Cholesteric materials display unique optical properties which can be exploited in opto-electronic applications such as light emitting diodes. The key feature is the position of the wavelength of the emitted light relative to the one of the selective reflection band. We have synthesized a set of cellulose derivatives displaying the cholesteric phase with the aim to investigate the correlation between chemical structure and properties. Phase transition temperatures, the chain packing, the wavelength of selective reflection but also absorption and fluorescence spectra were investigated as a function of the degree of substitution (DS), the nature of lateral substituents, the composition of doped systems and blends of different cellulose derivatives. Investigated were furthermore the degree of circular polarization of the emitted light for guest–host systems and for cellulose systems with chromophores linked by covalent bonds to the cellulose backbone as well as their performance in light emitting diodes. The conclusion is that the optical properties can be accounted for on the basis of the model of a one-dimensional photonic crystal. The limiting factor with respect to opto-electronic applications is the poor control of the uniformity of the helix formation and orientation. 相似文献
A method was proposed for differential determination of bound carboxylic acids in mixed cellulose esters containing residues of acetic and higher carboxylic (capric, lauric, myristic, palmitic) acids. 相似文献
New paths for the fast and reliable analysis of cellulose esters (CE) via subsequent functionalization and 1H NMR spectroscopy were studied. Perpropionylation of the CE is an inexpensive and efficient method. For cellulose diacetates used as representative ester well resolved 1H NMR spectra were obtained, which can be used for the calculation of the over all degree of substitution (DS) and the partial DS values at position 2, 3, and 6. No transesterification occurs during the subsequent acylation and a standard deviation of S2 = 1.32 x 10−4 was found for a series of experiments. In case of more complex ester structures especially with extended aliphatic moieties per-4-nitrobenzoylation need to be applied prior to NMR measurements. The spectra obtained can be completely assigned and applied for the calculation of DS values. 相似文献
The structure and sorption properties of gel films of bacterial cellulose were studied in its interaction with polyvinylpyrrolidone and silver nanoparticles stabilized by this compound. 相似文献
A series of blend films have been prepared from cellulose and corn protein in a NaOH/urea solution by a simple, low cost, and ‘green’ pathway. Their structure and properties are characterized by amino acid analysis, X‐ray diffraction, scanning electron microscopy, thermogravimetry, and tensile testing. The results reveal that a certain miscibility exists between cellulose and corn protein and their thermal stability and mechanical properties are improved significantly, compared with the protein materials, when the protein content is less than 18 wt.‐%. The protein, which contains tyrosine and histidine, could remain in the blend films after being washed for ten days, which indicates the strong hydrogen bonding between the hydroxy groups of cellulose and the hydroxyphenyl of tyrosine and imidazolyl of histidine in the protein. Furthermore, they exhibit good biocompatibility capable of supporting cell adhesion and proliferation.
Russian Journal of Applied Chemistry - Rheological properties of mixtures of dilute and moderately concentrated aqueous solutions of carboxymethyl cellulose with various degrees of ionization and... 相似文献
The solubility of flax fibers differing in the degree of purity in triethylamine N-oxide monohydrate was studied. The size and amount of the associates in equiconcentrated solutions were estimated from the turbidity spectra. Rheological properties of solutions of cotton and flax cellulose were compared. Hydrated cellulose films were obtained from solutions, and their physicomechanical properties were studied. The films were characterized by IR spectroscopy. 相似文献
Trends in the yields and properties of cellulose esters are studied as a function of wood esterification conditions. The yield, total extent of cellulose ester substitution, and degree of conversion depend on the duration and acylation temperature相似文献
In this work, ZnO nanoparticles loaded cellulose acetate (ZOLCA) films have been prepared and characterized by XRD, SPR and SEM analysis. The moisture permeation properties of the films have been investigated. The GAB isotherm model has been found to fit well on the moisture uptake data obtained at different temperatures. The monolayer sorption capacity χm was found to decrease from 0.059 to 0.0079 g water/g dry film with increase in temperature from 20 to 37°C. The isosteric heat of sorption, when studied in the lower water activity range of 0.04 to 0.10, was evaluated to be 46.55 to 87.29 kJ/mol. The water vapor permeability across the ZOLCA films was found to increase with temperature and activation energy of moisture sorption process was found to be 48.57 kJ/mol. These films have shown excellent antibacterial action against model bacteria E-Coli when investigated by qualitative and quantitative methods. Films exhibit great potential to be used as edible films to protect food stuff against microbial infections. 相似文献
Protocols for sputtering stoichiometric aluminum antimonide thin films were developed by calculating aluminum and antimony vapor condensation flux densities. Aluminum and antimony were sputtered separately. The high chemical reactivity of nanosized aluminum and antimony films made it possible to reduce the synthesis temperature considerably (far below the melting point of the compound). The synthesis involved thermal annealing. The reaction between aluminum and antimony films started at 470°С. Optimal AlSb formation parameters comprise annealing at 540°С for at least 10 h. Film synthesis steps were studied by X-ray powder diffraction, optical, electron, and atomic force microscopy. The composition was monitored by energy dispersive X-ray spectra. The films were found to have hole conductivity; the 300-K charge density and charge mobility in the films are 1 × 1019 cm–3 and 1 × 102 cm2/(V s), respectively. 相似文献
Summary: In this article we present some interesting properties of rodlike cellulose microcrystals (so‐called “whiskers”). These microcrystals can be obtained from different cellulose sources such as wood, cotton, or animal origin. When submitted to acid hydrolysis, the cellulose fibers yield stable aqueous suspensions because of the presence of negative charges on the surface of the microcrystallites during the hydrolysis process. The obtained microcrystals are rod‐shaped particles, the dimensions of which depend on the cellulose origin. For instance, the cotton whiskers have typical dimensions varying from 100 to 300 nm in length, L, and 8 to 10 nm in diameter, d, while those of the tunicate whiskers range from 100 nm to few micrometers in length and 10 to 20 nm in diameter. At very low concentrations, these whiskers are randomly suspended in water and form an isotropic phase. When the concentration reaches a critical value, the whiskers spontaneously display ordered phases showing interesting liquid crystal properties (nematic and chiral nematic). The chiral nematic orders can be retained after evaporation of the solvent (generally water), leaving iridescent films. The reflected color can be controlled by changing either the ionic strength or by applying an electric field. These colloidal particles have been investigated using several techniques including small‐angle neutron scattering (SANS), small angle X‐ray scattering, rheology, and more recently dynamic and static light scattering techniques (DLS and SLS) to highlight their static and dynamic behavior. Because of their geometry, important axis ratio (L/d), and high crystallinity, these rods have been also extensively used to process nanocomposites based on polymer matrices, to reinforce their mechanical properties. All these properties are discussed in this contribution.
Rodlike nanocrystals in aqueous suspension (left, Tunicate, 1 wt.‐%) and film (right), observed between cross‐polarizers. 相似文献
The regenerated cellulose (RC)biocomposite films were prepared using casting method where oil palm empty fruit bunch (OPEFB) and microcrystalline cellulose (MCC) were dissolved in N-dimethylacetamide/lithium chloride (DMAc/LiCl)solution. The increasing of OPEFB contents up to 2 wt% increased the tensile strength and modulus of elasticity of RC biocomposite films while the elongation at break decreased. However, at 3 and 4 wt% of OPEFB content, the tensile strength and modulus of elasticity decreased with increases OPEFB content, but elongation at break increased. The increment of tensile strength and modulus of elasticity at 2 wt% is due to the OPEFB fiber that partially dissolved and dispersed with the OPEFB matrix. The morphology studies illustrate that at 2 wt% of OPEFB content of biocomposite films surface consists less voids and agglomerations than at 4 wt%. This can be considered the RC filler was partially dispersed with the RC matrix in the biocomposite films. 相似文献