Water-soluble Cellulose Ether Research Articles

A Covalently Cross-Linked Hyaluronic Acid/Carboxymethyl Cellulose Composite Hydrogel as a Potential Filler for Soft Tissue Augmentation.

The use of fillers for soft tissue augmentation is an approach to restore the structure in surgically or traumatically created tissue voids. Hyaluronic acid (HA), is one of the main components of the extracellular matrix, and it is widely employed in the design of materials with features similar to human tissues. HA-based fillers already find extensive use in soft tissue applications, but are burdened with inherent drawbacks, such as poor thermal stability. A well-known strategy to improve the HA properties is to reticulate it with 1,4-Butanediol diglycidyl ether (BDDE). The aim of this work was to improve the design of HA hydrogels as fillers, by developing a crosslinking HA method with carboxymethyl cellulose (CMC) by means of BDDE. CMC is a water soluble cellulose ether, whose insertion into the hydrogel can lead to increased thermal stability. HA/CMC hydrogels at different ratios were prepared, and their rheological properties and thermal stability were investigated. The hydrogel with an HA/CMC ratio of 1/1 resulted in the highest values of viscoelastic moduli before and after thermal treatment. The morphology of the hydrogel was examined via SEM. Biocompatibility response, performed with the Alamar blue assay on fibroblast cells, showed a safety percentage of around 90% until 72 h.

Viscoelasticity and Solution Stability of Cyanoethylcellulose with Different Molecular Weights in Aqueous Solution.

Water-soluble cellulose ethers are widely used as stabilizers, thickeners, and viscosity modifiers in many industries. Understanding rheological behavior of the polymers is of great significance to the effective control of their applications. In this work, a series of cyanoethylcellulose (CEC) samples with different molecular weights were prepared with cellulose and acrylonitrile in NaOH/urea aqueous solution under the homogeneous reaction. The rheological properties of water-soluble CECs as a function of concentration and molecular weight were investigated using shear viscosity and dynamic rheological measurements. Viscoelastic behaviors have been successfully described by the Carreau model, the Ostwald-de-Waele equation, and the Cox–Merz rule. The entanglement concentrations were determined to be 0.6, 0.85, and 1.5 wt% for CEC-11, CEC-7, and CEC-3, respectively. All of the solutions exhibited viscous behavior rather than a clear sol-gel transition in all tested concentrations. The heterogeneous nature of CEC in an aqueous solution was determined from the Cox–Merz rule due to the coexistence of single chain complexes and aggregates. In addition, the CEC aqueous solutions showed good thermal and time stability, and the transition with temperature was reversible.

Controlled Release of Glucose from Orally Delivered Temperature- and pH-Responsive Polysaccharide Microparticle Dispersions

Dual-responsive polysaccharide microgel dispersions were synthesized by the self-assembly of a temperature-responsive water-soluble cellulose ether, hydroxypropyl cellulose (HPC), and a pH-responsi...

Use of viscous pore fluids in dynamic centrifuge modelling

The scaling laws that arise from dynamic centrifuge modelling contain an inconsistency regarding the scaling of time between dynamic and diffusion events. This problem can be resolved by reducing the permeability of the soil, with the help of high-viscosity pore fluids. Hydroxypropyl methylcellulose is a water-soluble cellulose ether that is widely used to create such fluids. In this paper, the effects that concentration, temperature, ageing and shearing rate have on the viscosity of hydroxypropyl methylcellulose solutions are examined and equations that quantify them are presented. This information is meant to act as a guideline for the preparation of high-viscosity pore fluids for dynamic centrifuge tests.

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

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

The Structure and Properties of Sulfo-Butylated Celluluse Ether (SBC) Based Water-Reducing Agents

Abandoned cellulose was treated with acid to prepare Micro-Crystalline Cellulose (MCC) holding affirmative polymerization, which was then treated with 1,4–butanesultone (BS) to synthesize water-soluble Sulfo-Butylated Cellulose ether (SBC). The structure of the SBC was characterized by means of FT-IR, 1H NMR, SEM, and XRD, and its relationship to function was investigated based on the polymerization of MCC and Degree of Substitution (DS). SEM images of hardened cement were also studied. The results indicated that when the polymerization of the MCC was smaller than 96 and the DS greater than 0.375, SBC exhibited water-reduction. When sulfonated cellulose was mixed into the cement paste, its retarding effect slowed hydration early in the aging process, so that later the structure of hardened cement paste became more uniform and compact than that of control.

Impact of water-soluble cellulose ethers on polymer-modified mortars

Cellulose ethers (CEs) are employed in many polymer-modified mortars, such as cement renders, masonry mortars, tile adhesives, repair mortars, skim coats, and self-levelling mortars. The addition of CEs to mortars causes the retardation of cement hydration and modifies the microstructural characteristics and the properties of these mortars. The present work attempts to provide a comprehensive review of the current state of knowledge on the effects of CEs and critically identifies gaps in the knowledge. A fundamental scientific understanding concerning the chemistry and hydration of cement, chemical natures, and relevant properties of CEs are discussed. The behaviours and mechanisms of CE adsorption on cement are assessed. The influences of CEs on the kinetics of cement hydration, mechanisms of retardation, and microstructural evolution of the mortars also are reviewed. Finally, the impact of CEs on the properties of fresh and hardened mortars as well as the approaches used to mitigate the negative impacts of CEs are discussed.

Novel polymer–polyphenol beads for encapsulation and microreactor applications

Novel structures with controllable morphology made from natural materials hold promise for several applications in pharmaceuticals, foods and biotechnology field. In this paper, we utilized the strong interactions between epigallocatechin gallate (EGCG), a polyphenol obtained from green tea, and water soluble cellulose ethers like methyl cellulose (MCE) and hydroxyl propyl methylcellulose (HPMC) to fabricate novel beads with controllable core–shell morphology. The novel polymer–polyphenol beads were prepared by simply adding polymer solution dropwise into an aqueous solution of polyphenol. Effect of process variables like concentration and viscosity grades of polymer, reaction time and concentration of EGCG on bead formation was evaluated. Spherical milky white beads with average diameters ranging from 600–2500 µm were obtained that retained shape after freeze drying. Internal structure of beads was studied using automated light microscopy and cold stage scanning electron microscopy (Cryo-SEM). Percent loading of EGCG in the beads was above 25% w/w in all the cases. The release study in simulated intestinal fluid revealed burst release of EGCG (20% in first 5 minutes) followed by sustained release with more than 90% release at the end of 300 minutes. The antioxidant power of EGCG in the beads was effectively maintained in the alkaline conditions with 5–6 fold activity as compared to free EGCG. Further, the temperature triggered release characteristic of beads was explored by encapsulating eucalyptus oil and studying the release of oil using hot stage microscopy. Enzyme immobilisation application of beads was demonstrated by immobilising α-amylase onto the beads and studying its enzyme activity after several washings.

Calculation of infrared spectra for conformers of a dimeric fragment of the 2,6-hydroxyethylcellulose macromolecule in aqueous solution

Based on both a complete calculation of normal vibration frequencies and absolute IR absorption band inten- sities of a dimeric fragment of the 2,6-hydroxyethylcellulose macromolecule and a comparison of the results with the corresponding experimental data, a detailed interpretation of the IR spectrum (1200-960 cm -1 ) of this polymer is given for the first time. Its conformational characteristics in aqueous solution at 20 and 70 o C were determined by the molecular dynamics method. It is shown that the changes observed in IR spectra of hydroxyethylcellulose in aqueous solutions upon heating may be connected with conformational transitions of the ether side groups. analysis, absolute intensities, spectrum interpretation. Introduction. Water-soluble ethers of cellulose (hydroxyethyl-, carboxymethyl-, methyl-derivatives) are widely used in various industrial sectors. Structural features, in particular, the number and location of ether groups on the pyranose ring and their rotational isomerization are responsible for the valuable properties of these compounds. Vibra- tional spectra (IR and Raman) can reveal even the most subtle structural changes in these macromolcules. Therefore, they are exceedingly effective for studying the structural organization of water-soluble ethers of cellulose (1-4). The reversible changes in the spectra that occur on changing the temperature of the polymers are not related to any chemi- cal transformations in the structure of these compounds and can be explained (5) by a change of the rotational iso- meric (conformational) structure of the macromolecules (6, 7). Studies of the conformational features of the side groups in water-soluble ethers of polysaccharides should establish structureproperty relationships for these practically important compounds. The goal of the present work was to determine the structure of side groups in a dimeric fragment of the water-soluble cellulose ether macromolecule 2,6-hydroxyethylcellulose (2,6-HEC) in aqueous solution at various tem- peratures, to calculate the frequencies and potential energy distribution (PED) of normal vibrations and absolute inten- sities of IR absorption bands, and to model the optical density spectrum of the most stable conformers of the ether groups of this fragment. Experimental Method. The stated problem was solved using a combined approach (8) to modeling IR spec- tra of organic compounds that used both molecular mechanics and quantum chemistry methods to calculate the fre- quencies of normal vibrations and absolute intensities of IR absorption bands, respectively, of polyatomic molecules. The algorithm for calculating the absolute intensities within the framework of the applied approach (as for using the valence force field approximation (8, 9)) consisted of calculating the derivatives of the electron-density P matrix over Decartes shifts of atoms and the matrix of derivatives ∂r ⁄ ∂Qi from Decartes shifts of atoms over normal coordinates and multiplying the resulting matrices. Shifts of atoms in Decartes coordinates in each normal vibration were calcu- lated using molecular mechanics (solution of the direct spectral problem). Matrices of charges on atomic nuclei, elec- tron densities, and bond orders were calculated using the CNDO/2 quantum-chemical method. The derivatives of these

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.

Towards elucidation of the drug release mechanism from compressed hydrophilic matrices made of cellulose ethers. II. Evaluation of a possible swelling-controlled drug release mechanism using dimensionless analysis

A swelling-controlled mechanism, based on the simple fitting of drug release data to a power law, is frequently invoked to explain deviations from Fickian diffusion. Therefore, the purpose of this work was to evaluate whether such a mechanism is possible in the case of compressed hydrophilic matrices made of cellulose ethers, using parameters that were independently obtained, either in Part I (Ferrero et al., [1]) or in the present study. The derivatives used were hydroxypropyl methyl celluloses, hydroxyethyl celluloses and hydroxypropyl celluloses of varying molecular mass. We investigated polymer chain relaxation (by mechanical testing and oscillatory rheology), the release characteristics of the model drug sodium salicylate, as well as the swelling behavior of the compressed tablets (front movements and water uptake). Assessment of a possible swelling-controlled release (relaxation-controlled, penetrant-activated) mechanism was based on the use of the Deborah number, De, and that of the swelling interface number, Sw. Two extreme polymer fractions were considered for the evaluation of De and Sw, namely those fractions that were assumed to be present at the swelling front and at the eroding front. Analysis of drug release data using the Korsmeyer–Peppas model resulted in diffusional exponent n values that were consistently greater than 0.44 (for the cylindrical geometry used here), which could thus indicate anomalous (coupled diffusion–relaxation) drug transport behavior. However, from the observed De values ≪ 1 (at both fronts), which are indicative of water Fickian diffusion in the rubbery polymer matrix, and the Sw values ≫ 1 (at the swelling front), which correspond to drug Fickian diffusion, we infer that a swelling-controlled drug release mechanism should be dismissed for such water-soluble hydrophilic cellulose ethers, i.e. polymer chain relaxation is not the rate-limiting step in the drug release process from this type of hydrophilic polymer. In fact, Sw values close to unity were calculated for the erosion front, but this is not a sufficient criterion for a swelling-controlled release mechanism. In addition, the dimensionless numbers calculated for the erosion front should be considered cautiously and conservatively since relaxation of the macromolecules is very unlikely to still occur when the latter are in the process of detaching from the polymer matrix. In addition, it was experimentally confirmed from the front positions that erosion is the phenomenon operating with this type of swellable polymer, concomitantly with Fickian diffusion. As surface erosion follows the same kinetics as the relaxational process, the coupled diffusion/erosion mechanism accounts for diffusional exponent n values greater than 0.50, 0.45 and 0.43 for the slab (film), the cylindrical (disk) and the spherical geometry, respectively, as calculated from drug release data using the power law equation.

Calcium carbonate growth in the presence of water soluble cellulose ethers

Calcium carbonate precipitation was performed in the presence of methyl cellulose (MC) and two kinds of hydroxyethyl cellulose (HEC FD-10000, HEC FD-30000). The results demonstrated that the final product morphology and structure of CaCO 3 crystals are highly sensitive to the concentration of the cellulose ethers aqueous solution. By precisely controlling their concentrations, all these three cellulose ethers solutions have the ability of protecting metastable vaterite from thermodynamically transforming into stable calcite. The intermediate products investigation showed to some extent the phase transformation of calcium carbonate in its growing process from metastable vaterite to calcite and indicated that the calcium carbonate crystal growth in HEC solutions occurs through dissolution and reprecipitation process. Calcium carbonate growth in both presence of HEC and ethanol or Mg 2+ was also examined. This work demonstrates the potential of water soluble cellulose ethers in controlling biominerals crystallization and growth. The results are revelatory for biomineralization and fabricating new organic–inorganic hybrids based on cellulose derivatives.

Synthesis and anaerobic biodegradation of indomethacin-conjugated cellulose ethers used for colon-specific drug delivery

Water soluble cellulose ethers, including methylcellulose and two hydroxyethylcelluloses with different molecular weights, were conjugate with indomethacin at room temperature. The chemical structures of the conjugates were characterized by FTIR, 1H NMR and UV–vis spectroscopy. The results confirmed that different amounts of IND residues were covalently bonded to cellulose ether backbones through ester linkages. Their anaerobic biodegradation in colonic fermentation was investigated by gel permeation chromatography, gas chromatography and UV–vis spectroscopy. These conjugates were found to have different biodegradabilities, depending on the cellulose ether used and the amount of conjugated indomethacin residues. In vitro release experiments showed that hydroxyethylcellulose-based conjugates with low IND residues content could exhibit a sustained drug release behavior in colonic fermentation and were stable in the simulated media of the stomach and small intestine. Therefore, they are promising candidates for future applications in colon-specific drug delivery.

Gelcasting of metal powders in nontoxic cellulose ethers system

A nontoxic gel system for gelcasting complex-shape metal green body was investigated. The process was based on the heat-initiated gelation characteristic of water-soluble cellulose ether (CE) or its hydroxyalkyl derivative in hydrotropic solution. In gelcasting, a highly loaded but very fluid suspension consisting of iron powder, water, antioxidant, dispersant and gelformer, was poured into a non-porous mould and gelled at 60 °C. The apparent viscosity of the suspension and factors influencing it were analyzed. The green bodies with bending strength of about 2.5 MPa had a smooth surface and homogeneous microstructure. After sintering, dense and uniform iron parts were successfully obtained.

Changes in the rheological properties of mixtures of water-soluble cellulose ethers under mechanical treatment

Changes in the rheological properties of mixtures of water-soluble cellulose ethers under mechanical treatment

Calculation of conformations and vibrational spectra of a monomeric fragment of the 2,6-carboxymethyl cellulose molecule

A theoretical conformational analysis has been carried out for the side substituents of a fragment of the molecule for 2,6-carboxymethyl cellulose (a water-soluble cellulose ether), and the frequencies and the potential energy distribution of the normal vibrations have been calculated for the most stable conformers of the ether groups of this fragment in the approximation of the molecular mechanics method. It has been shown that the most stable conformers are those that have the conformations gg, t, g−, g−, g−-for the groups of atoms on the bonds C5-C6, C6-O6, C13-O6, C10-C13, C10-O9 and the conformations g+g−, g+, g−, g−; g+g−, g−, g−, g−; g+g−, g−, g+, t for the groups of atoms on the bonds C2-O2, C11-O2, C7-C11, C7-O8. Comparative analysis of the calculated frequencies and the potential energy distribution of the normal vibrations for 13 of the most stable conformers showed, as in the case of the 2,6-hydroxyethyl cellulose molecule, that the frequencies and modes of the normal vibrations are highly sensitive to conformational transitions in the analyzed spectral region (800–1500 cm−1). The characteristic patterns for the change in the frequencies and modes of the normal vibrations have been established in connection with conformational transitions within both side substituents. The observed conformational lability of the bulky substituents in the cellulose ether molecules and its manifestations in the vibrational spectrum provide a basis for hypothesizing that one of the major mechanisms for the process of their thermal gelation in aqueous solutions is conformational transitions within these substituents.

Calculation of conformations and vibrational spectra of a fragment of the 2,6-hydroxyethyl cellulose molecule

We have used the molecular mechanics method for conformational analysis of a fragment of the molecule of a water-soluble cellulose ether: 2,6-hydroxyethyl cellulose (2,6-HEC). As a result of rotation about the C-C and C-O bonds within the bulky side substituents on the C5 and C2 backbone atoms in the fragment of the 2,6-HEC molecule, we have obtained 12 of the most stable conformers for this fragment with strain energies differing within the range 0–2.3 kcal/mol. We have shown that the most stable conformers have the following conformations for the groups of atoms on the bonds C5-C6, C6-O6, C13-O6, C10-C13: gt, g−, g+, g+ and gg, t, g+, g+ respectively; and on the bonds C2-O2, C11-O2, C7-C11: g+g−, g−, g+ respectively. For the conformers obtained, using the same method we calculated the frequencies and the potential energy distribution (PED) for their normal vibrations (NV). Comparative analysis showed high sensitivity of both the frequency and the PED of the normal vibrations to conformational changes within the indicated bulky substituents over the entire analyzed spectral region (800–1500 cm−1 for the methylene groups). We introduce the concept of “conformational characteristicity” of both the frequency and the mode of vibration. We show that it is possible to analyze the conformations of the bulky substituents of the fragment of the 2,6-HEC molecule using its vibrational spectrum.

Structural physicochemistry of polysaccharide molecules. Vibrational spectra and structure of water soluble cellulose and starch ethers

For the first time, complex study of the structure of practically important water soluble derivatives of cellulose and starch (carboxy methyl, hydroxy ethyl ethers) with the use of coupled calculations of conformations and vibrational spectra, FTIR and Raman spectroscopy, mathematical treatment of spectral curves (deconvolution, numerical differentiation) has been performed. It is shown that such a complex approach is very promising in thin-structural analysis of these complicated polymer objects.

Synthesis and characterization of graft copolymers of hydroxypropyl cellulose with acrylamide and some comonomers

AbstractTo obtain new polymeric materials for environmental management, we used pine needles from the huge forest of the Western Himalayas as a source of cellulose. Cellulose was derivatized to hydroxypropyl cellulose (HPC), a useful water‐soluble cellulose ether. HPC was graft‐copolymerized with acrylamide (AAm) with benzoyl peroxide as the initiator. At optimum grafting conditions, five different concentrations of the comonomers glycidyl methacrylate, acrylic acid, 2‐hydroxyethyl methacrylate, and acrylonitrile were grafted with AAm. Networks of HPC and AAm were also synthesized by crosslinking reactions with glutaraldehyde as a crosslinker over a range of four different concentrations of crosslinker under acidic conditions. Crosslinked networks of HPC with AAm and a comonomer at one comonomer concentration were also synthesized. Graft copolymers were characterized by Fourier transform infrared spectroscopy, scanning electron microscopy, and swelling behavior. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 91: 545–555, 2004

PH-dependent self-assembly: micellization and micelle-hollow-sphere transition of cellulose-based copolymers.

pH-Sensitive micelles are usually made from double-hydrophilic block copolymers which can dissolve molecularly in water in a certain pH range and aggregate spontaneously upon an appropriate change in the pH value. Significant advances in this field have been achieved in recent years.[1] Polymeric hollow spheres have great potential for the encapsulation of large quantities of guest molecules. Different approaches, such as by the use of block copolymers as precursors,[2] as well as colloidal particles[3a,b] or liposomes[3c,d] as templates, have been developed to obtain such nanocapsules. Our research group has produced micelles in which no chemical bonds connect the core and the shell,[4] thus enabling hollow spheres to be obtained by simple dissolution of the inner component of the micelles.[4a–c] However, these approaches are mostly irreversible, that is, once the hollow structure forms, the core–shell micelles cannot be reformed. Hydroxyethylcellulose (HEC) has been extensively studied as a nonionic and water-soluble cellulose ether (Scheme 1).[5] However, studies on the self-assembly of HEC are limited, despite its biocompatibility and biodegradability. Here we report the self-assembly of HEC-graftpoly(acrylic acid) (HEC-g-PAA) in water, which was prepared by free-radical graft polymerization of acrylic acid from HEC backbones (Table 1). The results demonstrate its micellization and the transition between micelles and hollow spheres; both processes were found to be pH-dependent and reversible. Figure 1 shows the relative scattering intensity I/I0 of the solutions of two HEC-g-PAA copolymers, CAA-1 and CAA2, as a function of the pH value (I0 is the intensity of the starting solution at pH 13.5). The two solutions exhibit a