Materials based on carbon-filled porous layers of PVC cyclam derivatives cross-linked with the surfaces of asbestos fabric fibers

The synthesis of bilayer materials with porous upper layers composed of PVC hydroxyethylcyclam derivatives filled with carbon and a layer consisting of hydroxyethylcyclam, cross-linked via Si–O–C groups with the silica chains of a developed surface of asbestos fabric, is described. The aza-crown groups in these materials are bound with aqua complexes of H₂SO₄ or NaOH. The structure of the materials is examined, their adsorption characteristics are determined, and the rate of motion of H⁺ or OH^– ions in electrochemical bridges is measured, while the formation of H₂ and O₂ in their cathodic and anodic polarization is determined as a function of voltage. It is shown that the upper layer of these materials is adsorption-active and electronand H⁺- or OH^–- conductive, while the bottom layer is only H⁺- or OH^–- conductive; through it, the upper layer is supplied with the H⁺ or OH^– ions needed for the regeneration of the aqua complexes broken down to H₂ and O₂ on carbon particles.     

Disperse dyes based on 2-aminothiazole derivatives for cellulose triacetate fabric

A range of azo disperse dyes was prepared by coupling diazotized 2-amino-4-(p-nitrophenyl)-5-nitrothiazole with various substituted arylamines. Spectral properties in the infrared and visible range of the dyes obtained were investigated. All the dyes, when applied on cellulose triacetate fabric as 2% shade, showed fairly good to very good light fastness and very good to excellent fastness to washing, perspiration, rubbing and sublimation. All the dyes gave a wide range of reddish brown to indigo shades with very good depth and levelness on fabric. The purity of dyes was checked by thin layer chromatography. The percentage dyebath exhaustion and fixation on fabric was reasonably good and acceptable.     

Photoluminescence from C60-coupled porous structures formed on Fe+-implanted silicon

111-oriented p-type Si wafer with a resistivity of 1-5 Omega cm was implanted with Fe+ and then annealed at 1100 degrees C in N2 for 60 min, followed by anodization in a solution of HF to form porous structure with beta-FeSi2 nanocrystallites. Photoluminescence (PL) spectral measurements show that a strong PL peak appears in the range of 610-670 nm. The position of the PL peak remains unchanged, but its intensity increases with the storage time in air until about three months and then saturates. C60 molecules were chemically coupled on the porous structure through a kind of silane coupling agent to form a nanocomposite. It is revealed that the stable PL peak monotonically shifts to a pinning wavelength at 570 nm. Experimental results from PL, PL excitation, Raman scattering, and x-ray diffraction measurements clearly show that the pinned PL originates from optical transition in C60-related defect states, whereas the photoexcited carriers occur in the beta-FeSi2 nanocrystallites formed during anodization. This work opens a new way to tailor nanometer environment for seeking optimal luminescent properties.     

Construction by molecular dynamics modeling and simulations of the porous structures formed by dextran polymer chains attached on the surface of the pores of a base matrix: characterization of porous structures

Significant increases in the separation of bioactive molecules by using ion-exchange chromatography are realized by utilizing porous adsorbent particles in which the affinity group/ligand is linked to the base matrix of the porous particle via a polymeric extender. To study and understand the behavior of such systems, the M3B model is modified and used in molecular dynamics (MD) simulation studies to construct porous dextran layers on the surface of a base matrix, where the dextran polymer chains and the surface are covered by water. Two different porous polymer layers having 25 and 40 monomers per main polymer chain of dextran, respectively, are constructed, and their three-dimensional (3D) porous structures are characterized with respect to porosity, pore size distribution, and number of conducting pathways along the direction of net transport. It is found that the more desirable practical implications with respect to structural properties exhibited by the porous polymer layer having 40 monomers per main polymer chain, are mainly due to the higher flexibility of the polymer chains of this system, especially in the upper region of the porous structure. The characterization and analysis of the porous structures have suggested a useful definition for the physical meaning and implications of the pore connectivity of a real porous medium that is significantly different than the artificial physical meaning associated with the pore connectivity parameter employed in pore network models and whose physical limitations are discussed; furthermore, the methodology developed for the characterization of the three-dimensional structures of real porous media could be used to analyze the experimental data obtained from high-resolution noninvasive three-dimensional methods like high-resolution optical microscopy. The MD modeling and simulations methodology presented here could be used, considering that the type and size of affinity group/ligand as well as the size of the biomolecule to be adsorbed onto the affinity group/ligand are known, to construct different porous dextran layers by varying the length of the polymeric chain of dextran, the number of attachment points to the base matrix, the degree of side branching, and the number of main polymeric chains immobilized per unit surface area of base matrix. After the characterization of the porous structures of the different porous dextran layers is performed, then only a few promising structures would be selected for studying the immobilization of adsorption sites on the pore surfaces and the subsequent adsorption of the bioactive molecules onto the immobilized affinity groups/ligands.     

Synthesis and proton conductivity of adsorption-saturated and solvated porous hydroxyethylated cyclam layers on the surface of PVC-coated cellulose fabric

Porous layers of associates of adsorption-saturated and benzene- and hexane-solvated chloride and sulfate of hydroxyethylated cyclams with acid aqua complexes were synthesized on the surface of PVC-coated cellulose fabric. The porous structure of the layers includes a system of internal pores connected with the external pores via the diamine rings of the common walls of the hydroxyethylated cyclam nets; the internal pores are filled with the associates; the solvent molecules are adsorbed on the developed surface of the layers or solvate it. The H⁺ motion rate in a layer placed in solvent vapors or liquid solvents was measured; the layers were found to be nonlinear H⁺ conductors. The potential of H⁺ transition from the acid solution into the layer, the H⁺ mobility constant, and the field variation constant of the H⁺ mobility of the layer depend on the layer composition. The adsorption and solvation are accompanied by the formation of host-guest molecular complexes between the diamine rings of the cyclam nets and the benzene or hexane molecules, affecting the resistance of the associates to the incorporation of H⁺ ions and the H⁺ mobility in the associates.     

Homogeneous and porous modified bacterial cellulose achieved by in situ modification with low amounts of carboxymethyl cellulose

To improve the rehydration ability of bacterial cellulose (BC), many macromolecules have been used as modifiers in previous reports. However, the aggregation of additives in the BC matrix appears to be inevitable. We investigated different parts of a BC pellicle, which was achieved by in situ modification with carboxymethyl cellulose (CMC) in culture with Gluconacetobacter xylinus ATCC53582 or Enterobacter sp. FY-07. We observed a concentration gradient of CMC in the BC pellicle from G. xylinus ATCC53582, but not with Enterobacter sp. FY-07. Low concentrations of CMC (0.01 %, m/v) are sufficient to modify BC in situ in culture with Enterobacter sp. FY-07, in which CMC could sufficiently contact with the newly formed BC. The crystallinity of the modified BC decreased by more than 39.8 %, and its rehydration ability and water holding capacity increased by 43.3 and 31.0 %, respectively. Unlike the pellicle of modified BC achieved from obligate aerobes, such as G. xylinus ATCC53582, that produced by Enterobacter sp. FY-07 exhibited better homogeneity and porosity.     

Design, synthesis, and application of a library of supramolecular structures formed by N-lipidated peptides immobilized on cellulose. Artificial receptors

An array of supramolecular structures formed from N-lipidated peptides attached to cellulose via aminophenylamino-1,3,5-triazine was synthesized. The structures thus prepared were prone to self-organization and to formation of monolayer of "holes" and "pockets" in dynamic equilibrium, structures which were capable of binding small guest molecules very efficiently recognizing the shape, size, and polarity of ligands, thus resembling artificial receptors. Because of the high flexibility of N-lipidated peptides, it is expected that the host adjusts its shape to wrap guest molecules most efficiently. The selectivity and rate of binding was studied by using triphenylmethyl dyes. It was found that the selectivity of binding depends on the structure of the peptide and the N-lipidic fragment of the receptor and varies with the structure of the analyte. Even tiny structural changes in guest molecules were detected by monitoring the alteration of the binding pattern.     

Determination by the enzyme thermistor of cellobiose formed on degradation of cellulose

A calorimetric assay procedure for the determination of cellobiose has been developed. The cellobiose is hydrolyzed by β-glucosidase and the glucose formed is measured calorimetrically by an enzyme thermistor containing co-immobilized glucose oxidase and catalase. The system was optimized with regard to the arrangement of the enzymes, the pH-dependence of the separate enzymic steps, and of the total system. By placing the β-glucosidase in a precolumn that could be switched in and out of the flow through the enzyme thermistor, both cellobiose and glucose present in the sample could be determined. The performance with standard solutions and with crude samples from cellulose degradation experiments was investigated.     

Rheology of PVC Plastisol--V: storage modulus and network formed by particle contact

Our previous work with PVC plastisols showed that pseudo-plastic behavior under increasing frequency of dynamic measurement was a result of the development of an immobilized layer. Subsequently, the dynamic viscosity and the storage modulus of the mobile phase were evaluated. The samples consisted of fine and coarse particles, of which the fine/coarse ratio was varied. The present work relates the storage modulus at different frequencies to the fine/coarse ratio through a model network consisting of particle-particle contacts. The contacts are of three kinds, fine-fine (f-f), fine-coarse (f-c), and coarse-coarse (c-c). The average number of contact points per particle has been evaluated for the above kinds of contacts at different frequencies. Also, a number of particles participating in the network have been evaluated as a relative measure. At lower frequency relatively larger numbers of f-f contact points exist per particle but fewer numbers of particles participate in the network. Therefore, the network is rather loose. The f-c contact shows a similar trend but fewer contact points per particle at all frequency levels. The c-c contact is limited to a pair formation, i.e., only 0.5 contact point per particle on average. However, c-c contact contributes significantly to the magnitude of the modulus, because of the size of the particle. At the higher frequency there are fewer f-f contacts, but a larger number of particles are participating in the network. The trend with the f-c contact is very similar. The c-c contact increases significantly at the higher frequencies.     

三氟甲基侧取代氧、氮、硫杂大环化合物的合成和 分子结构

合成了四个三氟甲基侧取代氧、氮、硫杂大环化合物,通过IR、^1HNMR、RS和元素分析作了表征;用AM1方法计算它们的电子结构,并根据计算结果给出了它们的几何构型。     

Layer-by-layer assembled thin films based on fully biobased polysaccharides: chitosan and phosphorylated cellulose for flame-retardant cotton fabric

Polyelectrolytes multilayer (PEM) films based on fully biobased polysaccharides, chitosan and phosphorylated cellulose (PCL) were deposited on the surface of cotton fabric by the layer-by-layer assembly method. Altering the concentration of PCL could modify the final loading on the surface of cotton fabrics. A higher PCL concentration (2 wt%) could result in more loading. Attenuated total reflection Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy and energy-dispersive X-ray analysis directly showed that chitosan and PCL were successfully deposited onto the surface of cotton fabric. In the vertical flame test, the cotton fabric with 20 bilayers at the higher PCL concentration (2 wt%) could extinguish the flame. Microcombustion calorimetry results showed that all coated cotton fabrics reduced the peak heat release rate (HRR) and total heat release (THR) relative to the pure one, especially for (CH0.5/PCL2)₂₀, which showed the greatest reduction in peak HRR and THR. Thermogravimetric analysis results showed that the char residue at temperatures ranging from 400 to 700 °C was enhanced compared to that in the pure cotton fabric, especially in the case of higher PCL concentration (2 wt%). The work first provided a PEM film based on fully biobased polysaccharide, chitosan and PCL on cotton fabric to enhance its flame retardancy and thermal stability via the layer-by-layer assembly method.     

Microstructural and mechanical properties of porous biocomposite scaffolds based on polyvinyl alcohol,nano-hydroxyapatite and cellulose nanocrystals

In this study, in situ synthesis of polyvinyl alcohol (PVA)/nano-hydroxyapatite (n-HA)/cellulose nanocrystals (CNC) organic–inorganic biocomposite porous scaffolds is reported. The effect of the CNC content on the properties of the biocomposite scaffold was investigated and characterized using field-emission scanning electron microscopy, Fourier-transform infrared spectroscopy (FTIR), X-ray diffraction (XRD) analysis, porosity and compressive strength measurements, thermal studies, and in vitro biomineralization and degradation studies. The morphological study showed highly porous structures with good pore interconnectivity in which n-HA was homogeneously dispersed. XRD analysis showed a decrease in the crystalline fraction and crystallite size of nano-hydroxyapatite with introduction of PVA and with increasing content of CNC. It was observed that the porosity decreased to some extent with increasing CNC content, while increases in the compressive strength (from 0.85 to 2.09 MPa) and elastic modulus (from 4.68 to 16.01 MPa) were found as the CNC content was increased. In vitro biomineralization study revealed the formation of apatite on PVA/n-HA/CNC biocomposite scaffolds when soaked for 7 and 14 days in simulated body fluid (SBF) solution. The obtained porous scaffolds offering good mechanical performance may provide a promising alternative scaffolding matrix for use in the field of bone tissue engineering.     

Covalent assembly of metal nanoparticles on cellulose fabric and its antimicrobial activity

We develop an antimicrobial active robust metal-cellulose nanohybrid by covalent assembly of metal nanoparticles on cellulose fabric using a simple impregnation of thiol-modified cellulose fabric in colloidal silver (Ag) or palladium (Pd) nanoparticle solutions. The combined results of high resolution transmission electron microscopy (HR-TEM), field emission scanning electron microscopy (FE-SEM), energy-dispersive X-ray spectroscopy (EDXS) and inductively coupled plasma atomic emission spectrometry (ICP-AES) reveal that the nanoparticles are highly loaded and dispersed in the thiol-modified cellulose fabric, and X-ray photoelectron spectroscopy (XPS) analysis reveals that the nanoparticles are immobilized in the fabric by a strong and stable covalent bond with thiol functional group. This robust covalent linkage between the nanoparticles and the fabric leads to a remarkable suppression of the release of metal nanoparticles from the fabric. In addition, the metal-cellulose nanohybrids show high antimicrobial activity in excess of 99.9 % growth inhibition of the microorganism. Thus, we anticipate that our metal-cellulose nanohybrid may not only protect cell damage caused by penetration and fixation of metal nanoparticles into the human body but also act as a sustainable biomedical textile.     

Molecular structures of compounds formed by benzo-15-crown-5 with calcium salts

X-ray structural and spectroscopic results are given on the compound formed by benzo-15-crown-5 with calcium perchlorate, Ca(ClO₄)₂·C₁₄H₂₀O₅·2H₂O; the combination does not involve any substantial change in the dihedral angles in the macrocycle, as the coordination sphere is constructed as a result of supplementing the positions occupied by the macrocycle oxygen atoms with three other atoms (oxygen atoms from the perchlorate group and two water molecules). The results are compared with published data on the structures of the compounds formed by benzo-15-crown-5 with NaClO₄, Mg(NCS)₂, CuCl₂, Ca(NCS)₂ and Ca(3,5-dinitrobenzoate)₂.Translated from Teoreticheskaya i Éksperimental' naya Khimiya, Vol. 24, No. 2, pp. 242–247, March–April 1988.     

Long-term stabilization of foams and emulsions with in-situ formed microparticles from hydrophobic cellulose

We report a simple method to produce foams and emulsions of extraordinary stability by using hydrophobic cellulose microparticles, which are formed in situ by a liquid-liquid dispersion technique. The hydrophobic cellulose derivative, hypromellose phthalate (HP), was initially dissolved in water-miscible solvents such as acetone and ethanol/water mixtures. As these HP stock solutions were sheared in aqueous media, micron sized cellulose particles formed by the solvent attrition. We also designed and investigated an effective and simple process for making HP particles without any organic solvents, where both the solvent and antisolvent were aqueous buffer solutions at different pH. Consequently, the HP particles adsorbed onto the water/air or water/oil interfaces created during shear blending, resulting in highly stable foams or foam/emulsions. The formation of HP particles and their ability for short-term and long-term stabilization of interfaces strongly depended on the HP concentration in stock solutions, as well as the solvent chemistry of both stock solutions and continuous phase media. Some foams and emulsion samples formed in the presence of ca. 1 wt% HP were stable for months. This new class of nontoxic inexpensive cellulose-based particle stabilizers has the potential to substitute conventional synthetic surfactants, especially in edible, pharmaceutical and biodegradable products.     

Gas permeation properties of A-type zeolite membrane formed on porous substrate by hydrothermal synthesis

A-type zeolite membranes were synthesized on a porous support tube by a hydrothermal process. The membranes were polycrystalline, and the thickness was in the range of 0.4–3.8 μm. They were stable against repeated temperature changes over the range 35–300°C. Permeances of the membranes, determined using He, H₂O, H₂, CO₂, O₂, N₂, CH₄ and C₃H₈, were dependent on the size of permeate, and the maximum H₂/N₂ separation factor was 4.8 for a mixed H₂–N₂ feed. This suggests the permeation was, at least in part, affected by a molecular sieving mechanism, although the membranes contained some pores larger than the structural pores of the zeolite.     

Aggregation of inclusion complexes formed by noncovalent columnar structures based on α- and γ-cyclodextrins and poly(alkylene glycols)

Kinetic analysis of the aggregation of complexes formed by columnar types of α- and γ-cyclodextrins (α-CD_col and γ-CD_col) and poly(alkylene glycols) is performed by the dynamic light scattering method. For comparison, analogous studies were conducted for systems containing initial α- and γ-cyclodextrins (α-CD and γ-CD). Upon the aggregation of systems containing α-CD, the number of nuclei with critical sizes slowly increases at the initial part of kinetic curve throughout the solution bulk; when some limiting concentration and sizes of formed aggregates are achieved, the system is transformed into the gel-like state. The aggregation of γ-CD_col-poly(ethylene glycol) system proceeds into two stages. At the first fast stage, aggregates are formed by particles representing single-strand inclusion complexes composed of one γ-CD_col molecule and two units of ethylene oxide. At the second, much slower stage, aggregates are formed by two-strand complexes composed of one γ-CD_col molecule and four units of ethylene oxide. It follows from the comparison of aggregative properties of γ-CD_col-poly(ethylene glycol) and γ-CD_col-poly(propylene glycol) systems that the rate of aggregation is much higher in the second case.     

Size-selective absorption and adsorption in anionic pigmented porous coating structures: case study cationic starch polymer versus nanofibrillated cellulose

The use of nano- or microfibrillar cellulose (NFC or MFC) in papermaking is generally hampered by high cost and potentially wasteful use in typical wet end applications. The solubility and fines nature of the material makes it inefficient to retain, and when retained it is generally inefficiently applied within the spatial distribution of the paper fibre matrix. The benefits of capturing the important NFC in a layer structure, to enhance surface and stiffness properties of paper, board and laminates whereby NFC is entrapped at the surface of a fibrous web by forming an in situ composite, were previously shown for the exemplified case of modified porous calcium carbonate, as might be used in an inkjet coating application (Ridgway and Gane in Cellulose 19(2):547–560, 2011). The NFC is seen to integrate itself within the larger interparticle porous structure providing excellent holdout and thin layer continuity, essential in developing an efficient concentration of the NFC at the surface of the substrate. The effect is likened to the well-known I-beam construction. The concept need not be confined to porous pigments, as any pigment coating structure that absorbs and holds the NFC, thus creating an in situ composite, could be used. The aim of this study is to look at a range of different pigments and investigate how these could be used as coating structures by measuring the effect on the pore structure before and after absorbing NFC. This is achieved by using model porous tablet blocks made from the respective anionic coating formulations. The penetration of cationic starch solution, as might be applied for surface sizing on paper, is studied for comparison. The use of cationic starch is considered in the industry to provide reasonably effective surface concentrations due to the electrostatically driven adsorption to the anionic pore surfaces. The effect of water alone on the coating structure has also been measured to allow for structural relaxation, considered to be mainly related to the swelling properties of the anionic polyacrylic coating pigment dispersant. The results illustrate the size-exclusion properties of the pore structure in relation to the material being absorbed and partial resistance to bulk penetration by pore wall adsorption in the case of oppositely charged species. The distribution of the absorbate throughout the pore network can be derived using mercury intrusion porosimetry and electron microscopy, and is deemed critical in respect to controlling the end performance properties, be they, for example, barrier, strength-enhancing applications, or both.     

Chromonic liquid crystals formed by CI Acid Red 266 and related structures

Chromonic liquid crystals are currently receiving increased attention because they have applications in a wide range of products. In this study, we have compared the chromonic mesophase behaviour of four azo dyes with similar chemical structures. Our objective is to determine if there is an obvious link between mesophase formation and dye chemical structure. Orange G does not form mesophases over the concentration range examined (saturated solution > ~20–30 wt%). The other three compounds all form nematic (N) and hexagonal (H) mesophases, but over very different concentration ranges. X-ray diffraction shows that the ordered Edicol Sunset Yellow (ESY) aggregates present in the mesophases have a single molecule cross section, while those of CI Acid Red have a cross section equivalent to six to eight molecules, probably organised in a ‘water-filled pipes’ structure. NMR quadrupole splittings of ²H₂O demonstrate that water binding to the aggregates is similar to that found for surfactant lyotropic mesophases. The sodium (²³Na) quadrupole splittings for Orange II and CI Acid Red are similar to the values found for surfactant hexagonal phases, suggesting that most sodium ions are ‘bound’ to the aggregates. This is unlike the behaviour of ESY where only one of the two sodium ions is bound.