Sorption Properties of Gel Films of Bacterial Cellulose

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.     

Some Properties of Polyelectrolyte-G rafted Cellulose

Anionic and cationic polyelectrolytes were grafted on a bleached kraft pulp. Grafting an anionic polyelectrolyte (sodium poly-acrylate-polyacrylamide copolymer) resulted in modified fibers possessing outstanding affinity for water and saline solutions in the pH range where the polymer is ionized. Swelling is the result of both the grafting operation itself and of the presence of the ionized polyelectrolyte.

The swollen grafted fibers could be disintegrated under intense shear to give a colloidal solution exhibiting pseudoplastic thixo-tropic behavior. Electron microscopic examination revealed that during the shearing process the fiber had been disintegrated into its constitutive elements, long rodlike protofibrils, which are believed to be mainly responsible for the high viscosities observed.

Grafting a cationic polyelectrolyte (polydimethylamino ethyl methacrylate hydrochloride) produced fibers with lower but significant water swelling. The influence of pH on swelling was similar, although reversed, to that observed with the anionic grafted fibers. The presence of a large number of cationic groups in the porous cellulose fiber gel points to applications in ion-exchange and adsorption processes.     

A Study on the Preparation,Structure, and Properties of Microcrystalline Cellulose

Abstract

The preparation, structure, and properties of microcrystalline cellulose (MCC) from rice straw were investigated by IR, x-ray, viscometry, polarizing microscope, SEM, etc. The results are as follows:

1. The leveling-off degree of polymerization (LODP) obtained from rice straw is about 80–150. The dimensions of MCC granules are 20–30 μm length, 0.5–0.8 μm thick, and the crystallinity is about 80%.

2. The aqueous suspension of a certain concentration of MCC can form a gel under the effect of shear force. The viscosity of MCC gel increased with an increasing content of MCC in water. A sharper increase of viscosity occurred in the 3–6% range.

3. The addition of one or two valence salts into the MCC gel increased the viscosity.

4. The viscosity of MCC gel has its maximum value at pH 8.

5. The MCC gel as an emulsifying agent can form a stable emulsion in the oil/water system when the ratio of oil/water is below 6/4.     

Water Sorption Properties and Antimicrobial Action of Zinc Oxide Nanoparticles-Loaded Cellulose Acetate Films

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 χ_m 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.     

消臭抗菌纤维素纤维的制备、结构和性能

采用一种制备消臭、抗菌纤维素纤维的新方法，即先将纤维素纤维用多元羧酸进行化学修饰，然后在铜溶液中处理，生成铜螯合纤维素纤维，用红外光谱、电子自旋波谱表征了该纤维的配位结构，消臭和抗菌实验结果显示，这种功能性纤维对硫化氢，氢气、三甲胺的消臭率分别达到100％，92．1％和80．4％，对金黄色葡萄球菌，大肠杆菌和白色念珠菌的抑菌率分别为79．14％，93．59％和82．50％，用X射线衍射，电子自旋波谱分析了该纤维吸附硫化氢，氨气、三甲胺的机理。     

Some Properties of Polycaprolactone Composites with Cellulose Nanocrystals

Russian Journal of General Chemistry - Composites of polycaprolactone with cellulose nanocrystals were produced, and their morphological, thermal, and strength characteristics were examined. It was...     

The Structure of Cellulose by Conformational Analysis. Part 5. The Cellulose Ii Water Sorption IsothermXS

Exact values of the sorption energies of single molecules of water on all available sorption sites of crystalline cellulose II have been obtained by conformational analysis. The sorption energies are equated to the total energy (E_tot ) of interaction between the water molecule and all the suitable atomic groups of the cellulose. E_tot is composed of van der Waals, H-bond, and electrostatic energies. The interferences of water molecules on vicinal sorption sites were obtained. Sites in which such interference can occur were identified for crystalline cellulose II. Sorption energy in crystalline cellulose II appears to depend only on the interaction of water with surface sorption sites of the crystal. There appears to be favorable sorption on 1) sites exerting high attractive forces, and 2) sites which are exposed and protrude from the crystal surface. Sites recessed from the crystal surface are generally repulsive due to strong interactions with neighboring groups. All the sorption energies of the “monolayer” were calculated. Very strong sorption sites cannot always form a second layer because of strong steric hindrance from vicinal groups. Sorption capacities of crystalline cellulose II were calculated, and the isotherm of the schematic five chain crystallite used was constructed by theoretical means. The results obtained were briefly compared with those for cellulose I crystallites and amorphous cellulose. The inflection points of the isotherm and the variability of Dent's k ₁ constant for the water monolayer with relative humidity for the cellulose I and II isotherms were also calculated by theoretical means.     

Structure and Transport Properties of Films of Mixed Cellulose Esters

Cellulose acetomyristates of varied composition were studied. The sample volume abnormally increases in high-temperature stretching and after swelling in benzene. Cellulose acetomyristates can be used as membranes for separating aromatic and aliphatic hydrocarbons.     

均相与非均相法合成的纤维素乙酸酯结构与性能的比较研究

研究了离子液体中均相反应制备纤维素乙酸酯(CA_(Homo))与非均相反应制备纤维素乙酸酯(CA_(Hete))的化学结构,进而比较了化学结构差别对纤维素乙酸酯性能的影响.均相与非均相法制备的CA化学结构存在显著差异,CA_(Homo)相比CA_(Hete)具有更好的均匀性,且CA_(Homo)和CA_(Hete)的取代基分布不同,CA_(Homo)的乙酰基取代顺序为C-6C-3C-2,CA_(Hete)的乙酰基取代顺序为C-3C-2C-6.同时对CA_(Homo)和CA_(Hete)的结晶行为、溶解性和热性能进行研究,结果表明,不同化学结构对CA的这些宏观性能影响较小,CA_(Homo)和CA_(Hete)均为无定型结构,可溶解于极性有机溶剂中,玻璃化转变温度和热稳定性相近.因此,通过离子液体均相制备的CA与现有非均相法制备的CA具有相似的物理性能,但均相法制备的CA结构均匀性更好.     

Effect of Structural and Electrolytic Properties of Carboxyl-Containing Cellulose Cationites on the Sorption of Cephalexin from Aqueous Solutions

Sorption of antibiotic cephalexin from aqueous solutions by monocarboxyl cellulose (MCC) samples with various content of carboxyl groups and structure (the degree of crystallinity) is studied. It is disclosed that the sorption occurs mainly due to electrostatic interactions via the proton transfer from carboxyl group of MCC to the carboxylate ion of cephalexin. The sorption is characterized by Langmuir isotherms and described by the equation of localized stoichiometric sorption. Sorption of cephalexin increases with the content of carboxyl groups in the sorbent phase, which is explained by the peculiarities of the dissociation of MCC carboxyl groups. Structural characteristics of MCC samples do not substantially influence the sorption of antibiotic. Dependence of the sorption value on the pH of equilibrium solution has a maximum at pH 3.5, which is explained by the specific features of the electrolytic dissociation of cephalexin and MCC.     

Kinetics of Antibiotic Sorption by Monocarboxyl Cellulose

Kinetics of the sorption of lincomycin and gentamicin from aqueous solutions of their salts and bases, as well as a cephalosporin group antibiotic cephalexin having the zwitterionic nature, by monocarboxyl cellulose is studied. It is disclosed that the sorption of the studied antibiotics is characterized by a combined diffusion type of kinetics. Effective diffusion coefficients (D _eff) are determined, and it is shown that they correspond to the times (t _1/2) of half-equilibrium establishment and increase with passing from lincomycin to gentamicin and, further, to cephalexin. The D _eff and t _1/2 values are found to depend on solution pH and the degree of cellulose sorbent swelling.     

Rodlike Cellulose Microcrystals: Structure,Properties, and Applications

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.     

Study of Sorption Properties of Amorphous Zirconium Phosphate

Amorphous zirconium phosphate ion-exchanger has been prepared in our laboratory according to the procedure given by Gal and Gal. The Chemical composition has been determined. Some chemical properties; stabilities and sorption of mono- to hexavalent cations have been studied in detail. It was found that washing the zirconium phosphate ion exchanger with alcohol before drying would increase the exchange capacity of amorphous zirconium phosphate.     

水可分散体羧甲基纤维素醋酸丁酸酯结构与性能研究

采用大浴比碱化、醚化与半均相酯化的合成方式,制备出纤维素混合醚酯——羧甲基纤维素醋酸丁酸酯（CMCAB）。利用^1H—NMR、FTIR、XRD、TG和DSC等技术对CMCAB结构与热性能进行分析与表征,并对其溶液表面性能、水分散体流变性能进行了研究。结果表明,CMCAB分子链上亲水性羧基分布均匀;CMCAB结晶度低、热...     

Structure and Properties of Bacterial Cellulose Produced Using a Trickling Bed Reactor

Structure and properties of bacterial cellulose (BC) produced by trickling fermentation were studied. The following indexes, such as extrinsic shapes, microstructure, chemical structure, purity, water holding capacity, porosity, and thermogravimetric characteristics, are recommended for assessing the structure and properties of bacterial cellulose. With the comparison to bacterial cellulose produced by static fermentation and shaking fermentation, the results showed that for different BC cultivation methods, the extrinsic shapes, synthetic mode, and microstructure were different. The basic consistency of the infrared spectrogram from three kinds of bacterial cellulose reflected that the chemical structures were very similar. But the –OH associating degree of trickling fermentation BC was higher, and the polymerization degree, purity, water holding capacity, porosity, and thermal stability of trickling fermentation BC were also higher than those of static fermentation BC and shaking fermentation BC. But the crystallinity and crystal grain size of trickling fermentation BC were less than those of static fermentation BC and greater than those of shaking fermentation BC and plant fiber. These above structure and properties of trickling fermentation BC could reference bacterial cellulose’s application in food and material field.     

A Highly Connected Porous Coordination Polymer with Unusual Channel Structure and Sorption Properties

Making connections : A hydroxy‐centered trinuclear nickel cluster has been employed to construct a highly connected, highly symmetric framework with a uninodal nine‐connected topology. An array of triakis tetrahedra leads to a biporous intersecting‐channel system (see picture).

     

Preparation of Arabinoxylan and its Sorption on Bacterial Cellulose During Cultivation

The sorption of arabinoxylan (AX) on bacterial cellulose was investigated by adding AX to the culture medium of Gluconacetobacter xylinus. The starting AX material was produced by alkaline extraction of oat spelts. To investigate the impact of varying AX quality, the residual lignin was reduced by ClO₂ bleaching. Furthermore, bleached and unbleached xylans were subjected to xylanase hydrolysis in order to produce fractions of varying molar mass. Of all samples only the water soluble fractions were used for sorption experiments. A reduced molar mass resulted in a lower sorption of AX to the cellulose, while the lignin content increased the sorption of AX on bacterial cellulose. The sorption of AX resulted in a reduction of bacterial cellulose crystallinity and cellulose Iα content. In combined treatments of AX with xyloglucan and β-glucan no synergistic effect of those polysaccharides on the AX sorption was found.     

致孔剂聚乙二醇对纤维素中空纤维膜结构与性能的影响

以离子液体氯代1-烯丙基-3-甲基咪唑（[AMI M]Cl）为溶剂纺制纤维素中空纤维膜,考察了聚乙二醇（PEG）分子量及其质量分数对中空纤维膜结构与性能的影响。采用场发射扫描电子显微镜（FESEM）对膜内、外表面形态结构进行了观察,测试了中空纤维膜的水通量、截留率等渗透性能以及最大拉伸强度、断裂伸长率等力学性能。结果表...     

若干新型结构和新的成键方式的金属羰基簇合物

本文介绍了几位作者所合成并用X射线单晶结构分析表征的五类新型Fe,Co,Ru羰基簇合物。讨论其成键方式与结构特点。并介绍某些具有双键的配位基以不同的断裂方式提供不同的分子片配位于原子簇骨架的情况。