Properties of Aqueous Solutions of Mixtures of Methyl Cellulose and Hydroxypropyl Cellulose

Rheological properties of dilute and moderately concentrated aqueous solutions of mixtures of methyl cellulose and hydroxypropyl cellulose and gelation in these solutions were studied. Using the solvent vapor sorption, the compatibility of the polymer pair was examined and the composition range in which the thermodynamic compatibility is realized was determined.     

Properties of the methyl cellulose-polyvinylpyrrolidone binary system in solution and in the solid state

Rheological properties of dilute and moderately concentrated aqueous solutions of methyl cellulose-polyvinylpyrrolidone blends, as well as the conditions of gelation in them, were studied. Films were obtained from solutions of the polymer blends, and their physicomechanical properties were examined. The range of the compositions corresponding to thermodynamic compatibility of methyl cellulose with polyvinylpyrrolidone was identified by the solvent vapor sorption method and by thermomechanical examinations of the films.     

Properties of aqueous solutions of methyl cellulose-polyvinyl alcohol blends

Rheological properties of dilute and moderately concentrated aqueous solutions of methyl cellulose-polyvinyl alcohol blends, as well as the conditions of gelation in these solutions were studied. The compatibility of the polymers was examined by the solvent vapor sorption method; the range of the compositions corresponding to thermodynamic compatibility of methyl cellulose and polyvinyl alcohol was identified.     

Comparative Study of Solutions and Gels of Sodium Carboxymethyl Cellulose Produced from Cotton and Wood Cellulose

Viscosity and gelation characteristics of aqueous solutions of sodium carboxymethyl cellulose produced from cotton and wood cellulose were studied.     

Behavior of Methyl and Propyl Methyl Cellulose Solutions in Longitudinal and Convergent Flows

A mixed ether, propyl methyl cellulose with varied number of propyl groups, was synthesized from commercial water-soluble methyl cellulose. The effect of the number of side propyl groups on the dynamics of aqueous methyl and propyl methyl cellulose solutions in longitudinal and convergent flows was studied. The conditions under which solutions transform into the induced anisotropic state were determined.     

Thermal gelation of cellulose in a NaOH/thiourea aqueous solution

Utilizing a novel solvent of cellulose, 6 wt % NaOH/5 wt % thiourea aqueous solution, for the first time, we prepared the thermally induced cellulose gel. We investigated the thermal gelation of cellulose solutions with rheometry and the structure of the gel with 13C NMR, wide-angle X-ray diffraction, environmental scanning electron microscopy, and atomic force microscopy. The cellulose solutions revealed an increase in both the storage modulus (G') and the loss modulus (G") with an increase in the temperature during gelation. The temperature at the turning point, where G' overrides G" because of the onset of gelation, decreased from 38.6 to 20.1 degrees C with an increase of cellulose concentration from 4 to 6 wt %. Given enough time, G' of all solutions can exceed G" at a certain temperature slightly lower than the gelation temperature, indicating that the occurrence of the gelation is also a function of time. Each of the assigned peaks of NMR of the cellulose gel is similar to that of the cellulose solution, suggesting that the gelation resulted from a physical cross-linking. The gels were composed of relatively stable network units with an average diameter of about 47 nm. At either a higher temperature (at 60 degrees C for 30 s) or a longer gelation time (at 30 degrees C for 157 s), the gel in the 5 wt % cellulose solution could form. A schematic gelation process was proposed to illustrate the sol-gel transition: the random self-association of the cellulose chains having the exposed hydroxyl in the aqueous solution promotes the physical cross-linking networks.     

Properties of solutions and films of blends of water-soluble cellulose ethers with Zosterin

Viscosity characteristics of dilute and moderately concentrated solutions of blends of methyl cellulose, hydroxyethyl cellulose, and carboxymethyl cellulose with Zosterin were studied. Composite films were prepared from solutions of the polymer blends; their IR spectra and physicomechanical and thermomechanical properties were studied. The region of thermodynamic compatibility of cellulose ethers with Zosterin was determined by solvent vapor sorption.     

Characteristics of Aqueous Solutions of Methyl Cellulose-Polymethacrylamidoglucose Mixtures

The characteristics of dilute (0.1%) and moderately concentrated (2%) aqueous solutions of methyl cellulose, polymethacrylamidoglucose, and their blends, and also the composition of films based on them were studied by viscosimetry, rheology, and IR spectroscopy. The effect of the mixture composition on the conditions of gel formation in methyl cellulose solutions was studied.     

Influence of processing parameters on regeneration kinetics and morphology of porous cellulose from cellulose–NaOH–water solutions

The kinetics of cellulose regeneration in acetic acid bath from cellulose–8% NaOH–water solutions and gels is studied as a function of gelation conditions, acid concentration and bath temperature. The diffusion coefficient of NaOH from cellulose solution or gel into regenerating bath was calculated. It does not depend either on gelation mode or on acid concentration. On the contrary, cellulose regeneration from non-gelled solutions is slower than from a gel. The increase in bath temperature induces diffusion coefficient increase obeying Arrhenius law. Scanning electron microscopy images of regenerated swollen-in-water freeze-dried cellulose and of the same samples dried in supercritical CO₂ show highly porous morphology. CEMEF is a Member of the European Polysaccharide Network of Excellence (EPNOE), .     

Temperature-concentration conditions of liquid-crystalline-phase formation in cellulose ethers and esters in trifluoroacetic acid

The temperature-concentration conditions of formation and regions of liquid-crystalline-phase existence in concentrated solutions of methyl cellulose, hydroxypropylmethyl cellulose, cellulose diacetate, and cellulose triacetate in trifluoroacetic acid are studied via optical methods. It is shown that the type of anisotropic structures is largely determined by the pitch of the cholesteric helix. An increase in the strength of acetate films corresponding to the maximum optical anisotropy in the two-phase region of transition of cellulose acetates solutions to the LC phase is found.     

Properties of solutions and films of blends of water-soluble cellulose ethers with poviargol

Rheological properties of moderately concentrated aqueous solutions of blends of methyl cellulose and carboxymethyl cellulose with Poviargol antiseptic (nanodispersed silver stabilized with polyvinylpyrrolidone) were studied. Composite films were prepared from solutions of the polymer blends, and the physicomechanical and thermomechanical properties of the films were examined. The region of thermodynamic compatibility of cellulose ethers with Poviargol was determined by the method based on sorption of solvent vapor.     

Influence of lignin on cellulose-NaOH-water mixtures properties and on Aerocellulose morphology

Microcrystalline cellulose and organosolv lignin, both dissolved in 8%NaOH-water, were mixed with the objective to study the influence of lignin on the properties of cellulose solutions and on the morphology of dry porous materials. Mixture viscosity and gelation were investigated. Cellulose-lignin gels were regenerated in aqueous acid baths and dried under supercritical CO₂ to obtain Aerocellulose, an aerogel-like material. The presence of lignin in the mixture speeded up gelation. During regeneration part of lignin was washed out. This created large pores and channels in the dry materials. The overall results obtained showed that cellulose and lignin are not compatible in the solvent used.     

Properties of blends of methyl cellulose and carboxymethyl cellulose with different degrees of ionization in solutions and solids

The rheological properties of dilute and moderately concentrated aqueous solutions of methyl cellulose with carboxymethyl cellulose having different degrees of ionization, were examined. The solvent vapor sorption method was applied to examine the compatibility of the polymers in the solid state and elucidate how the amount of nonionized carboxy groups in carboxymethyl cellulose affects its compatibility with methyl cellulose.     

Properties of mixed aqueous solutions of methyl cellulose with polyethylene oxide and of composite films prepared from them

Rheological properties of mixed dilute and moderately concentrated aqueous solutions of methyl cellulose with polyethylene oxide were studied. Composite films were prepared from these solutions, and their physicomechanical properties and structural organization were examined.     

Investigation of the structure of cellulose in LiCl/DMAc solution and its gelation behavior by small-angle X-ray scattering measurements

Cellulose gels were prepared from cellulose in lithium chloride/N,N-dimethylacetamide (LiCl/DMAc) solution. When the cellulose concentration in the solution is above the one at which cellulose molecules overlap, cellulose gels were formed. While the gel prepared by the addition of water was turbid, the one prepared by the ion exchange was colorless, transparent, and optically anisotropic. In order to explain this gelation behavior of cellulose, small-angle X-ray scattering (SAXS) measurements of the cellulose solutions and the gels were performed. The SAXS profiles of the cellulose solutions and the gels suggested that the large-scale fluctuation of the molecular chain density in the solution can be the origin of the molecular aggregates formed in the gel. Furthermore, the differences in the structure of the gels at the macroscopic and the molecular level were discussed in terms of the phase separation and the molecular association.     

Structure of Aqueous Methyl and Propyl Methyl Cellulose Solutions in the Initial Stage of Gelation

Evolution of the supramolecular associate structure of moderately concentrated aqueous methyl and propyl methyl cellulose solutions, as dependent on the degree of substitution by propyl groups, is studied by the polarized light scattering using the Debye-Bueche-Stein theory.     

Properties of Some Chitosan-containing Blends and Films Therefrom

Mixed solutions of chitosan and polymers with different chain rigidities (polyvinyl alcohol and methyl cellulose) in 2% acetic acid, at various component ratios, were studied viscometrically. The compatibility of the components in solutions and in the solid phase was assessed, and the mechanical characteristics of films prepared from these blends were determined.     

Preparation of cellulose hydrogels via self-assembly in DMAc/LiCl solutions and study of their properties

Cellulose-based hydrogels have been prepared from solutions of hardwood and flax lignocelluloses and cotton cellulose in an N,N-dimethylacetamide–lithium chloride (DMAc/LiCl) mixture by regeneration and subsequent self-assembly of cellulose chains. The main physicochemical characteristics of the hydrogels have been investigated. It has been shown that they can retain large amounts of water (up to 2500 wt %) and have high porosity and specific surface area. The studied hydrogels are classical stable 3D structures; however, unlike other hydrogels, they possess high stability in aqueous medium and irreversibility of gelation.     

Characteristics of composite films based on methyl cellulose and poly(N-vinylformamide) prepared from solutions in water and dimethyl sulfoxide

The stress-strain characteristics of composite films based on methyl cellulose and poly(vinylformamide) prepared from solutions of polymer blends in water and dimethyl sulfoxide are studied. The temperature of relaxation transitions in the mixed films and the concentration interval where the polymers are compatible are defined via the thermomechanical method and dynamic mechanical analysis. The effect of the nature of a solvent on the mechanism of crystallization of methyl cellulose, the stress—strain characteristics of the composite films, and the compatibility between the polymers is investigated.     

Characterization of Highly Porous Materials from Cellulose Carbamate

Highly porous cellulose was formed by gelation of cellulose carbamate solutions in caustic soda. Two methods for gel preparation were optimized for the formation of beads and bulky materials – the chemical precipitation from dilute sulfuric acid and the thermal gelation by annealing at elevated temperatures. Various methods were used for characterizing of the pores of low density materials: scanning electron microscopy, small angle X-ray scattering, mercury intrusion and nitrogen sorption. These methods were optimized and used for characterizing the complete pore system from micro to macro pores. The effects of different preparation (cellulose carbamate concentration in caustic soda) and processing (precipitation, drying and pyrolysis) on the pore structure were studied by the set of complementary methods. Aerocell samples with a minimum density of 0.06 g/cm³ were prepared from cellulose carbamate. They are characterized by a broad pore size distribution ranging from 0.5 nm to 1 mm, specific internal surfaces of up to 660 m²/g and total pore volumes of up to 18 cm³/g.