lithium-chloride and dimethylacetamide

Size exclusion of cellulose in LiCl/N,N-dimethylacetamide has been used for the past 15 years, yet much of the current research is still devoted to fundamental studies, as many issues regarding column calibration, separation mechanisms and solution behavior have not been resolved yet. The paper reviews practical aspects of sample preparation and it is demonstrated that sample heating and several techniques to aid solvent exchange call for reevaluation. It is further shown that the use of internal standard may introduce minor improvements in repeatability. The commonly used column calibration procedures, chromatographic conditions and applications are also reviewed. Further research is needed to understand the mechanisms of separation, to optimize column calibration and to facilitate and optimize sample preparation.

Topics: Acetamides; Calibration; Cellulose; Chromatography, Gel; Lithium Chloride; Molecular Conformation; Molecular Structure; Molecular Weight; Polysaccharides

The purpose of this study was to improve methane generation from corn stalk (CS) through alkaline hydrogen peroxide and lithium chloride/N,N-dimethylacetamide (AHP-LiCl/DMAc) pretreatment. Changes in the structures of treated and untreated CSs were investigated, and biomass components, including cellulose, hemicellulose and lignin, were analysed. Our findings revealed that AHP-LiCl/DMAc pretreatment improved accumulative methane yield by forceful delignification and effectively destroyed the structure of cellulose. The AHP-LiCl/DMAc-treated group had a maximum methane yield of 318.6 ± 17.85 mL/g volatile solid, which was 40.08% and 10.10% higher than the maximum methane yields of the untreated and AHP-treated group, respectively. This result showed enhanced cellulose dissolution by the ionic solvent of LiCl/DMAc and improved enzymatic saccharification in fermentative bacteria without structural modifications. The AHP-LiCl/DMAc treated group had higher glucose level, acetate followed by biomethanation process. Furthermore, the decrease in crystallinity indexes for AHP-LiCl/DMAc treated group was reported. Overall, this investigation proved a promising pretreatment approach for enhancing the degradation of CS into reducing sugars and improving methane generation.

Topics: Acetamides; Hydrogen Peroxide; Hydrolysis; Lithium Chloride; Zea mays

Fully dissolved cellulose samples are a requirement for reliable size exclusion chromatography (SEC). Although most of the standard dissolving pulps can be completely dissolved in the N,N-dimethylacetamide/lithium chloride (DMAc/LiCl) solvent system, some cellulose samples (e.g., regenerated cellulose fibers) have poor solubility and therefore have a limited access to molar mass measurements. For improving the latter, different activation steps have been developed. In order to obtain complete solutions for subsequent SEC analysis, the scope of this study was to further improve established methods by elucidating the major influential factors of sample preparation. In addition, the degree of stretching in artificial fibers was examined for viscose fibers. Therefore, activation steps in DMAc or dimethyl sulfoxide (DMSO) and subsequent dissolution in DMAc/LiCl were analyzed with swelling and dissolution kinetics. The time needed for maximum swelling was found to be the optimum activation time. Turbidity measurement was introduced to observe dissolution kinetics as an indicator of dissolution quality. Thus, the duration, as well as the number of steps toward dissolution, was optimized to enhance the throughput in the overall analysis of a large variety of hitherto poorly soluble cellulose samples. A comparison of the MMDs of completely soluble reference materials obtained with the intensified conventional method, and the developed method demonstrated that the latter has no adverse influence on the results.

Topics: Acetamides; Cellulose; Lithium Chloride; Molecular Weight; Solubility; Solvents

Lithium chloride (LiCl)/N,N-dimethylacetamide (DMAc) solvent system was used to dissolve native and pretreated wheat straw materials in order to promote the enzymatic hydrolysis process. The dissolution ratio of wheat straw in LiCl/DMAc solvent system increased when dilute sulfuric acid or ethanol-sulfuric acid mixture pretreatment was conducted before dissolution. The materials regenerated from LiCl/DMAc solution exhibited obvious changes in structure and morphology, as revealed by scanning electron microscopy (SEM) and X-ray diffraction (XRD) analysis. The cellulose and xylan digestibilities of regenerated materials were improved obviously. The cellulose digestibilities of materials regenerated from native and pretreated wheat straw by dilute sulfuric acid and ethanol-sulfuric acid mixture were 61.8, 81.2, and 84.4 %, respectively, with 25 FPU of cellulase and 187 IU of xylanase after 96 h. These values were significantly higher than the digestibilities of 0, 33.2, and 57.5 % obtained from corresponding materials before dissolution. Dissolution treatment of wheat straw by LiCl/DMAc solvent system provides an alternative method for efficient enzymatic hydrolysis.

Topics: Acetamides; Cellulase; Cellulose; Ethanol; Hydrolysis; Lithium Chloride; Solvents; Spectroscopy, Fourier Transform Infrared; Sulfuric Acids; Triticum

The regeneration of cellulose from microcrystalline cellulose/DMAc·LiCl solutions through thermal induced sol-gel transition and longtime gelation resulted in the formation of wholly cellulose I with a crystallinity as high as 84.7%.

Topics: Acetamides; Cellulose; Gels; Lithium Chloride; Solutions; Spectrum Analysis, Raman; Temperature; X-Ray Diffraction

Freeze-dried microfibrillated cellulose (MFC) was directly dissolved in 8.0% w/w lithium chloride/N,N-dimethylacetamide (LiCl/DMAc), and MFC/LiCl/DMAc solutions with accurate MFC concentrations were prepared. The different MFC solutions were diluted to 1.0% and 0.5% w/v LiCl/DMAc, and subjected to size-exclusion chromatography with multiangle laser-light scattering and refractive index analyses (SEC/MALLS/RI), and off-line RI analysis to determine their refractive index increments (dn/dc). Chitin, cellulose triacetate, a poly(styrene) standard, and cellobiose were used for comparison. Each of the two determination methods gave different dn/dc values for MFC and chitin but similar dn/dc values for cellulose triacetate and poly(styrene). The anomalously small dn/dc values of MFC and chitin were explainable in terms of stable cellulose-LiCl and chitin-LiCl structures (i.e., formation of apparent covalent bonds between hydroxyl groups and LiCl) in the solutions. Thus, the SEC/MALLS/RI method provides reliable molecular mass parameters for cellulose and chitin.

Topics: Acetamides; Cellobiose; Cellulose; Chitin; Chromatography, Gel; Lithium Chloride; Molecular Weight; Polystyrenes; Refractometry; Solubility; Solvents

The homogeneous tosylation of agarose was studied with respect to the effects of reaction parameters, such as reaction medium, time, and molar ratio, on the reaction course, the degree of substitution (DS) with tosyl/chloro deoxy groups, and the molecular structure. Tosyl agaroses (TOSA) with DS tosyl ≤ 1 .81 could be obtained in completely homogeneous reactions by using N,N-dimethylacetamide (DMA)/LiCl or 1,3-dimethyl-2-imidazolidinone (DMI) as solvents. The products were characterized by FT-IR and NMR spectroscopy and it was demonstrated that two types of substitution pattern can be achieved: (i) non-preferential substitution at position 6 of the 1 → 3-linked β-d-galactose unit (G-6) and position 2 of the 1 → 4-linked 3,6-anyhdro-α-L-galactose unit (LA-2) and (ii) regioselective tosylation at G-6, depending on whether the reaction is performed with or without LiCl. Finally, the nucleophilic displacement reaction of TOSA was studied using azide and ethylenediamine as representative nucleophiles. Novel deoxy-agarose derivatives were obtained that showed an interesting solubility behavior and will be used for creating functional polysaccharide materials.

Topics: Acetamides; Chemistry Techniques, Synthetic; Galactose; Imidazoles; Lithium Chloride; Sepharose; Tosyl Compounds

All-cellulose nanocomposites, comprising two different forms of cellulose nanowhiskers dispersed in two different matrix systems, are produced. Acid hydrolysis of both tunicate (T-CNWs) and cotton cellulose (CNWs) is carried out to produce the nanowhiskers. These nanowhiskers are then dispersed in a cellulose matrix material, produced using two dissolution methods; namely lithium chloride/N,N-dimethyl acetamide (LiCl/DMAc) and sodium hydroxide/urea (NaOH/urea). Crystallinity of both nanocomposite systems increases with the addition of nanowhiskers up to a volume fraction of 15 v/v%, after which a plateau is reached. Stress-transfer mechanisms, between the matrix and the nanowhiskers in both of these nanocomposites are reported. This is achieved by following both the mechanical deformation of the materials, and by following the molecular deformation of both the nanowhiskers and matrix phases using Raman spectroscopy. In order to carry out the latter of these analyses, two spectral peaks are used which correspond to different crystal allomorphs; cellulose-I for the nanowhiskers and cellulose-II for the matrix. It is shown that composites comprising a LiCl/DMAc based matrix perform better than NaOH/urea based systems, the T-CNWs provide better reinforcement than CNWs and that an optimum loading of nanowhiskers (at 15 v/v%) is required to obtain maximum tensile strength and modulus.

Topics: Acetamides; Cellulose; Cotton Fiber; Lithium Chloride; Mechanical Phenomena; Nanocomposites; Sodium Hydroxide; Stress, Mechanical; Urea

Photochromic azobenzene cellulose ethers were prepared by homogeneous etherification of cellulose with 2,3-epoxypropoxy-azobenzene (EA) in N,N-dimethylacetamide/lithium chloride solution. The EA with epoxy group could highly efficiently react with cellulose to synthesize 3-azobenzyloxy-2-hydroxypropyl-cellulose (Azo-cellulose) ethers with controllable degree of substitution (DS(azo)). The DS(azo) was in a range of 0.2-2.0 adjusted by the molar ratio of EA to anhydroglucose unit of cellulose. The Azo-celluloses with DS(azo)≥0.53 were soluble in aprotic solvents like dimethylsulfoxide. Their chemical structures and properties were characterized by elemental analysis, FT-IR, NMR, and thermogravimetric analysis. They showed reversible trans-cis-trans transition when Azo-cellulose/DMAc solutions were irradiated by successive irradiation of UV and visible light. The transition between trans- and cis- isomers could be effectively controlled by simply adjusting the irradiation time. The photo-stimulated trans-cis-trans conformational change induced conformation transition between rod-like shape of trans-isomer and skewed shape of cis-isomer.

Topics: Acetamides; Azo Compounds; Biocompatible Materials; Cellulose; Dimethyl Sulfoxide; Ethers; Lithium Chloride; Magnetic Resonance Spectroscopy; Photochemical Processes; Solubility; Spectroscopy, Fourier Transform Infrared; Stereoisomerism; Thermogravimetry; Ultraviolet Rays

Various sodium bacterial cellulose sulfates (SBCS) were prepared via the homogeneous sulfation of bacterial cellulose (BC) with a SO3/pyridine (Py) complex in a dimethyl acetamide/lithium chloride solution. The SBCSs were characterized using Fourier transform infrared spectroscopy, X-ray diffraction (XRD), carbon nuclear magnetic resonance spectroscopy, gel permeation chromatography, elemental analyses, and thermal gravimetric analyses. A variety of conditions (including various amounts of SO3/Py, temperatures, and reaction times) were utilized to obtain SBCSs with DS values that ranged from 0.10 to 1.50. The XRD profiles indicated that the SBCSs had a cellulose II analog polymorphous structure. The differences between BC and microcrystalline cellulose (MC) were studied in their respective reactions. BC is more reactive than MC in both the sulfation and depolymerization processes. The order of reactivity for COH is C6>C2>C3 for both BC and MC. Cellulose sulfates with DS values >0.31 were soluble in deionized water.

Topics: Acetamides; Bacteria; Cellulose; Chemistry Techniques, Synthetic; Drug Stability; Lithium Chloride; Molecular Weight; Pyridines; Solubility; Sulfur Oxides; Temperature; Water

Understanding the interactions between solvent molecules and cellulose at a molecular level is still not fully achieved in cellulose/N,N-dimethylacetamide (DMAc)/LiCl system. In this paper, cellobiose was used as the model compound of cellulose to investigate the interactions in cellulose/DMAc/LiCl solution by using Fourier transform infrared spectroscopy (FTIR), (13)C, (35)Cl, and (7)Li nuclear magnetic resonance (NMR) spectroscopy and conductivity measurements. It was found that when cellulose is dissolved in DMAc/LiCl cosolvent system, the hydroxyl protons of cellulose form strong hydrogen bonds with the Cl(-), during which the intermolecular hydrogen bonding networks of cellulose is broken with simultaneous splitting of the Li(+)-Cl(-) ion pairs. Simultaneously, the Li(+) cations are further solvated by free DMAc molecules, which accompany the hydrogen-bonded Cl(-) to meet electric balance. Thereafter, the cellulose chains are dispersed in molecular level in the solvent system to form homogeneous solution. This work clarifies the interactions in the cellulose/DMAc/LiCl solution at molecular level and the dissolution mechanism of cellulose in DMAc/LiCl, which is important for understanding the principle for selecting and designing new cellulose solvent systems.

Topics: Acetamides; Cellobiose; Electric Conductivity; Hydrogen Bonding; Ions; Lithium Chloride; Magnetic Resonance Spectroscopy; Models, Molecular; Protons; Solvents; Spectroscopy, Fourier Transform Infrared; Vibration

Naturally occurring cellulose is crystalline as a consequence of the strong interactions between the glucan chains that comprise it and therefore is insoluble in most solvents. One of the few solvent systems able to dissolve cellulose is lithium chloride (LiCl) dissolved in N,N-dimethylacetamide (DMA). By an integrated application of all-atom molecular dynamics (MD) simulations, reaction path optimization, free-energy calculations, and a force-matching analysis of coarse-grained atomistic simulations, we establish that DMA-mediated preferential interactions of Li(+) cations and Cl(-) anions with glucan chains enable cellulose dissolution in LiCl/DMA. The relatively weak solvation of Li(+), Cl(-), and glucan chains by DMA results in strong effective interactions of Li(+) and Cl(-) ions with the glucans, leading to cellulose dissolution. The small size of the Li(+) cations allows them to strongly couple to multiple interaction sites on the glucan chains of cellulose, including the spatially restricted regions around the ether linkages connecting neighboring glucose residues. Li(+) cations were thus identified as the main component responsible for driving cellulose dissolution. The mechanism for explaining the solubility of cellulose in the LiCl/DMA system deduced from the analysis of atomistic-scale simulations conducted in this work is also consistent with most of the empirical observations related to cellulose dissolution in salt/amide solvent systems.

Topics: Acetamides; Amides; Cellulose; Glucans; Ions; Lithium Chloride; Molecular Dynamics Simulation; Salts; Solubility

Water-soluble (1→3)-β-d-glucans with 1,6-linked branches (SBG) isolated from the cell walls of Saccharomyces cerevisiae were studied by size exclusion chromatography (SEC) with multi-angle laser light scattering (MALLS) detector using dimethylacetamide (DMAc) containing 0.5% (0.12M) LiCl, or dimethyl sulphoxide (DMSO) in the absence and presence of 0.25M LiCl, respectively, as eluents. The aggregating glucan could be dispersed as single chains in both solvents, with chain length distributions in reasonable agreement with results obtained previously with carboxymethylated glucans in aqueous solvent. However, DMAc is preferred over DMSO because of higher sensitivity in MALLS, and also because the latter produces SEC anomalies. SBG dissolves slowly in DMAc/LICl at room temperature, but heating accelerates the process. The rate of depolymerisation of SBG in DMAc/LiCl at high temperatures (70-105°C) was determined as a basis for defining dissolution procedures at elevated temperatures with a minimum of degradation. The result of the investigation is a simple and reliable protocol for preparing unaggregated, fully dissolved and undegraded SBG in DMAc/LiCl, which is well suited as a standard analysis of the molecular weight distribution of SBG-like molecules without chemical derivatization.

Topics: Acetamides; Chromatography, Gel; Dimethyl Sulfoxide; Glucans; Light; Lithium Chloride; Scattering, Radiation; Solubility

Pure quaternary tetraalkylammonium chlorides with one long alkyl chain dissolved in various organic solvents constitute a new class of cellulose solvents. The electrolytes are prepared in high yields and purity by Menshutkin quaternization, an inexpensive and easy synthesis route. The pure molten tetraalkylammonium chlorides dissolve up to 15 wt% of cellulose. Cosolvents, including N,N-dimethylacetamide (DMA), may be added in large excess, leading to a system of decreased viscosity. Contrary to the well-established solvent DMA/LiCl, cellulose dissolves in DMA/quaternary ammonium chlorides without any pretreatment. Thus, the use of the new solvent avoids some disadvantages of DMA/LiCl and ionic liquids, the most extensively employed solvents for homogeneous cellulose chemistry.

Topics: Acetamides; Ammonium Chloride; Cellulose; Lithium Chloride; Quaternary Ammonium Compounds; Solvents; Viscosity

The dissolution behaviour of disassociated cellulosic materials in N,N-dimethylacetamide/lithium chloride (DMAc/LiCl) was investigated. The parameters monitored were chromatographic elution profiles and recovered mass by means of gel permeation chromatography (GPC) with RI detection. In order to elucidate the impact of the disassembly on cellulosic fibres, comparative studies were performed with the non-disassociated cellulose counterparts. The importance of the presence of water was addressed by Karl Fischer titration and solvent exchange experiments. Morphological changes during the dissolution process were studied by scanning electron microscopy (SEM). Dissolution of fibrillated cellulosic materials is impeded compared to the non-fibrillated material. This is a consequence of the high-surface-area fibrils prone to retain high amounts of water. Dissolution behaviour of nano-crystalline cellulosic materials appeared to be source-dependent. Due to the absence of entangled networks, these materials retain only water bound at the surface of the nano-crystallites, indicative of both the exposed surface area and solubility. The small cellulose nano-particles extracted from dissolving pulp show lower solubility compared to the large NCC particles from cotton.

Topics: Acetamides; Cellulose; Chromatography, Gel; Cotton Fiber; Kinetics; Lithium Chloride; Microscopy, Electron, Scanning; Nanoparticles; Solubility; Water

Cellulose acylation by anhydrides (ethanoic to hexanoic) plus tosyl chloride, TsCl, or imidazole in LiCl/N,N-dimethylacetamide solution has been studied. Contrary to a previous claim, TsCl does not catalyze acylation. For the diazole-catalyzed reaction, N-acylimidazole is the acylating agent. Third order rate constants (k(3); 40-70 °C) have been calculated from conductivity data and split, by using information from model compounds, into contributions from the primary- (k(3;Prim(OH))) and secondary- (k(3;Sec(OH))) hydroxyl groups of cellulose. Values of k(3,Prim(OH))/k(3,Sec(OH)) are >1, and increase linearly as a function of increasing the number of carbon atoms of the acyl group. Rate constants and the degree of biopolymer substitution decrease on going from ethanoic- to butanoic-, then increase for pentanoic- and hexanoic anhydride, due to enthalpy/entropy compensation. Relative to the uncatalyzed reaction, the diazole-mediated one is associated with smaller enthalpy- and larger entropy of activation, due to difference of the acylating agent.

Topics: Acetamides; Acylation; Anhydrides; Catalysis; Cellulose; Entropy; Imidazoles; Kinetics; Lithium Chloride; Tosyl Compounds

The tosylation of cellulose in ionic liquids (ILs) was studied. Due to the beneficial effect of different co-solvents, the reaction could be performed at 25°C without the need of heating (in order to reduce viscosity) or cooling (in order to prevent side reactions). The effects of reaction parameters, such as time, molar ratio, and type of base, on the degree of substitution (DS) with tosyl- and chloro-deoxy groups as well as on the molecular weight were evaluated. Products with a DStosyl≤1.14 and DSCl≤0.16 were obtained and characterized by means of NMR- and FT-IR spectroscopy in order to evaluate their purity and distribution of functional groups within the modified anhydroglucose unit (AGU). Tosylation of cellulose in mixtures of IL and a co-solvent was found to result in predominant substitution at the primary hydroxyl group. Size exclusion chromatography (SEC) revealed only a moderate degradation of the polymer backbone at a reaction time of 4-8h. Finally, the nucleophilic displacement (SN) of tosyl- and chloro-deoxy groups by azide as well as recycling of the ILs was studied.

Topics: Acetamides; Allyl Compounds; Cellulose; Chromatography, Gel; Dimethyl Sulfoxide; Ethylamines; Imidazoles; Ionic Liquids; Lithium Chloride; Magnetic Resonance Spectroscopy; Organophosphates; Pyridines; Solvents; Spectroscopy, Fourier Transform Infrared; Tosyl Compounds

Solutions of chitin in Li(+)/N,N-dimethylacetamide systems were studied via viscometry, using LiCl concentrations of 3% and 5% (m/v) and chitin concentrations ranging from 0.075 to 0.375 gL(-1). The reduced viscosity number versus concentration plot showed a minimum that was related to the formation of Li(+)-OC complex moieties along chitin macromolecular chains. Viscosity behavior was affected by temperature according to the Eyring model: concentration dependence of flow enthalpy of activation was correlated to polymer-polymer interactions and flow entropy of activation to the stiffness of the complexed chitosan macromolecular chain.

Topics: Acetamides; Chitin; Lithium Chloride; Molecular Structure; Solvents; Temperature; Viscosity

6-Azafulleroid-6-deoxy-2,3-di-O-myristoylcellulose (3) was synthesized from 6-azido-6-deoxycellulose (1) by two reaction steps. The myristoylation of compound 1 with myristoyl chloride/pyridine proceeded smoothly to give 6-azido-6-deoxy-2,3-di-O-myristoylcellulose (2) in 97.0% yield. The reaction of compound 2 with fullerene (C(60)) was carried out by microwave heating to afford compound 3 in high yield. It was found from FT-IR, (13)C NMR, UV-vis, differential pulse voltammetry (DPV), SEC analyses that compound 3 was the expected C(60)-containing polymer. Consequently, maximum degree of substitution of C(60) (DS(C60)) of compound 3 was 0.33.

Topics: Acetamides; Cellulose; Chromatography, Gel; Fullerenes; Lithium Chloride; Microwaves; Pyridines; Spectrophotometry; Thermogravimetry

The 3,5-dimethylphenylcarbamate derivatives of cellulose bearing 3-(triethoxysilyl)propyl residues were immobilized in a capillary format onto a monolithic silica support by intermolecular polycondensation of the triethoxysilyl groups. The resulting columns were used for chiral separations using capillary electrochromatography. The effects of the synthesizing solvent, the selector coating procedure, the chiral selector concentration onto the silica monolith and the mobile phase pH value, on the separation of enantiomers were studied. The column-to-column reproducibility and stability also were evaluated. A test set of 14 chiral substances, including acidic, neutral, bifunctional and basic compounds, was used to investigate the effects of the factors mentioned above. Twelve pairs of enantiomers showed enantioselectivity at some of the different conditions tested. The column-to-column repeatability was satisfactory, and the prepared columns were stable under the adopted analysis conditions.

Topics: Acetamides; Acetonitriles; Capillary Electrochromatography; Cellulose; Hydrogen-Ion Concentration; Lithium Chloride; Pharmaceutical Preparations; Phenylcarbamates; Reproducibility of Results; Silicon Dioxide; Stereoisomerism

Lignocellulosic biomass is a plentiful and renewable resource for fuels and chemicals. Despite this potential, nearly all renewable fuels and chemicals are now produced from edible resources, such as starch, sugars, and oils; the challenges imposed by notoriously recalcitrant and heterogeneous lignocellulosic feedstocks have made their production from nonfood biomass inefficient and uneconomical. Here, we report that N,N-dimethylacetamide (DMA) containing lithium chloride (LiCl) is a privileged solvent that enables the synthesis of the renewable platform chemical 5-hydroxymethylfurfural (HMF) in a single step and unprecedented yield from untreated lignocellulosic biomass, as well as from purified cellulose, glucose, and fructose. The conversion of cellulose into HMF is unabated by the presence of other biomass components, such as lignin and protein. Mechanistic analyses reveal that loosely ion-paired halide ions in DMA-LiCl are critical for the remarkable rapidity (1-5 h) and yield (up to 92%) of this low-temperature (

Topics: Acetamides; Bioelectric Energy Sources; Biomass; Fructose; Furaldehyde; Furans; Glucose; Lignin; Lithium Chloride

Enzymatic glyco-modification of transparent cellulose films with lactose was achieved by nonaqueous biocatalysis, and rat hepatocyte attachment behavior to the lactose-modified cellulose films was investigated. Regenerated cellulose films were incubated with lactose using a surfactant-enveloped cellulase in lithium chloride/dimethylacetamide solvent at 37 degrees C for 24 h, and lactose molecules were successfully introduced to the cellulose films. The initial cell adhesion on the lactose-modified cellulose films was superior to the original cellulose film. In the absence of serum, hepatocytes were significantly attached only on the lactose-modified cellulose films. This process was markedly suppressed by the addition of free lactose as an inhibitor. These results suggest that such cell adhesion proceeded through a direct interaction between galactose residues on the cellulose films and asialoglycoprotein receptors on the rat liver cell surface. This novel approach for surface glyco-modification of a cellulose matrix and its biofunctional properties are expected to provide potential application as a bioactive scaffold for cell culture engineering.

Topics: Acetamides; Animals; Biocatalysis; Cell Adhesion; Cell Culture Techniques; Cellulose; Hepatocytes; Lactose; Lithium Chloride; Macromolecular Substances; Materials Testing; Membranes, Artificial; Rats; Surface Properties; Time Factors; Tissue Scaffolds

Never-dried cellulose gel obtained by slow coagulation from LiCl/N,N-dimethylacetamide (DMAc) solution was exposed to an alternating current electric field. Making use of the birefringence of oriented cellulose and by means of wide-angle X-ray scattering, it was demonstrated that preferred orientation of cellulose molecules parallel to the electric field lines is induced in the cellulose gel. The preferred orientation remained unchanged for several days after storage in water and persisted after drying of the cellulose gel.

Topics: Acetamides; Biocompatible Materials; Cellulose; Electromagnetic Fields; Gels; Lithium Chloride; Materials Testing; Scattering, Radiation; Solutions; X-Rays

We investigated the effect of solvent exchange on the supramolecular structure and the molecular mobility of the cellulose molecule to clarify the mechanism of the dissolution of cellulose in lithium chloride/N,N-dimethylacetamide (LiCl/DMAc). Among the celluloses that were solvent exchanged in different ways, the DMAc-treated celluloses dissolved most rapidly. Dissolution of the acetone-treated celluloses was much slower than the DMAc-treated ones, but considerably faster than the untreated one. Such differences in the dissolution behavior were well explained by the differences in the surface fractal dimension calculated from the small-angle X-ray scattering profiles and in the (1)H spin-lattice and spin-spin relaxation times estimated from the solid-state NMR spectroscopic measurements. Furthermore, it was suggested from the IR spectra and the (13)C spin-lattice relaxation times of cellulose that DMAc is adsorbed on the surface of cellulose even after vacuum-drying and affects the molecular mobility and hydrogen-bonding state of cellulose.

Topics: Acetamides; Acetone; Algorithms; Cellulose; Hydrogen Bonding; Lithium Chloride; Magnetic Resonance Spectroscopy; Scattering, Small Angle; Solubility; Solvents; Spectroscopy, Fourier Transform Infrared; X-Ray Diffraction

Topics: Acetamides; Cellobiose; Cellulase; Cellulose; In Vitro Techniques; Lithium Chloride; Pulmonary Surfactants; Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization; Surface-Active Agents; Trichoderma

Novel bulky esters of cellulose were synthesized homogeneously, applying the solvent systems DMA/LiCl or DMSO/TBAF, by conversion of the biopolymer with aryl polyester dendrons. The carboxylic acid moieties were efficiently activated in situ with CDI or the acid chloride was applied. Cellulose esters with DS values of up to 0.7 were obtained. The functionalization pattern was analyzed by different NMR spectroscopic techniques indicating that not only position 6 (primary hydroxyl group) but also the secondary one at position 2 was included in the reaction.

Topics: Acetamides; Carbohydrate Conformation; Cellulose; Dendrimers; Dimethyl Sulfoxide; Esters; Imidazoles; Lithium Chloride; Magnetic Resonance Spectroscopy; Models, Biological; Molecular Conformation; Molecular Structure; Quaternary Ammonium Compounds; Solvents; Spectroscopy, Fourier Transform Infrared; Temperature; Time Factors; Water

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.

Topics: Acetamides; Cellulose; Gels; Lithium Chloride; Scattering, Radiation; Solutions

The structure of a semidilute solution of mercerized cellulose (CC1m) in 8% (w/w) LiCl.DMAc, which contained some aggregates, was investigated using static and dynamic light scattering measurements. The static scattering function of the polymer solution containing a small amount of aggregates can be separated into fast- and slow-mode components by combining static and dynamic light scattering measurements. The osmotic modulus was identical for the fast-mode component of the CC1m solutions and the native cellulose (CC1) solutions, in which cellulose is dispersed molecularly. This indicates that the molecularly dispersed component of the CC1m solutions has an identical conformation with the cellulose molecules in the CC1 solutions. The correlation length was also identical for the fast-mode components of CC1m solutions and the CC1 solutions, indicating that these solutions have the same mesh size of the polymer entanglement. These observations for the fast-mode components are consistent with the concentration dependence of the zero shear rate viscosity and the plateau modulus estimated in the rheological measurements. The slow-mode component, on the other hand, gave information on the aggregate structure in the CC1m solution. The radius of gyration of the aggregate structure estimated from the slow-mode component was about 70 nm, which is independent of the concentration of the solution. The plots for particle scattering factor of the slow-mode component lay between the theoretical curve of a sphere and a Gaussian chain, implying that the structure of the aggregate in the CC1m solution is like a multiarm polymer. A characteristic time of the slow-mode component calculated with the translational diffusion coefficient and the radius of gyration were almost identical with the relaxation time of the long-time relaxation observed in the rheological measurements. This indicates that the long-time relaxation of CC1m solutions originates in the translational diffusion of the aggregate structure in the solution.

Topics: Acetamides; Cellulose; Light; Lithium Chloride; Rheology; Scattering, Radiation; Solutions

Enthalpic phenomena were shown to contribute to the size exclusion separation mechanisms during chromatographic analysis of solutions of pullulan and cellulose in LiCl-N,N-dimethylacetamide (LiCl-DMAc) solvent and eluent. The effect of LiCl concentration in the sample solutions and the effect of temperature were of the same order of magnitude for both pullulan and cellulose samples. This led to systematic errors in the determination of mean molecular mass in the range of tens of percent, depending on the chromatographic conditions and on the molecular mass of the analyte. The systematic error is much higher than the random errors; the typical values of the latter being up to a few percent (RSD). Low column temperature and a higher content of LiCl in the sample solution led to lower determined mean molecular mass values. This can be explained by a decrease in the interactions between dissolved macromolecules, although polymer-stationary phase interactions should also be taken into account. Furthermore, the cellulose stability in solution was determined: the zero order random degradation constant being k = 6.9 x 10(-8) mol mol-1 monomer day-1.

Topics: Acetamides; Cellulose; Chromatography, Gel; Glucans; Lithium Chloride; Thermodynamics

Solutions in N,N-dimethylacetamide (DMAC)-LiCl were prepared from two different pulps (sulphite pulp from softwood and cotton linters) in different ageing states. Degradation of the stirred solutions at 35-40 degrees C was observed by determining the molecular masses by size exclusion chromatography (SEC). We showed that under these conditions cellulose and holocelluloses are degraded in DMAC-LiCl and that the rate of degradation is dependent on the temperature and the initial state of degradation of the sample. Temperature and dissolution time are recommended to be reduced, especially for aged samples.

Topics: Acetamides; Cellulose; Chromatography, Gel; Lithium Chloride; Solutions

Commercial rayon grade cellulose was dissolved in the lithium chloride-N,N-dimethylacetamide (LiCl-DMAc) solvent system and esterified with acetic anhydride using p-toluenesulfonyl chloride (p-TsCl) and pyridine as catalysts. The reaction temperature was varied from 28 to 70 degrees C and the time of reaction from 2 to 24 h. Full substitution took place at 60 and 70 degrees C at respective reaction times of 10 and 8 h for p-TsCl, and 10 and 6 h for pyridine. Esterification of cellulose followed a second-order reaction path. The rate constants at different reaction temperatures and the activation energy for the reaction are reported. Mechanisms for these reactions using the two catalysts are also suggested. The degrees of substitution (DS) of the esters prepared using both catalysts show that pyridine is a better catalyst than p-TsCl. Molecular weights of the esters, determined viscosimetrically, show that some degradation in the cellulose chain occurred at a reaction temperature of 70 degrees C. Hence, the optimum temperature for esterification appears to be 50-60 degrees C at 10 h reaction time to obtain full degree of acetyl substitution.

Topics: Acetamides; Carbohydrate Conformation; Catalysis; Cellulose; Esters; Kinetics; Lithium Chloride; Models, Molecular; Solvents; Temperature; Thermodynamics

Microcrystalline cellulose was chlorinated with N-chlorosuccinimide-triphenylphosphine under homogeneous conditions in LiCl-N,N-dimethylacetamide. At the early stage of the reaction only replacement of the 6-hydroxyl groups with chlorine was observed, and 3-hydroxyl groups were replaced at a lower rate with Walden inversion. The effects of reaction conditions on the extent of chlorination were studied in detail. More than two equivalents of chlorination reagents per glucose residue were necessary to attain a high degree of substitution (ds) by chlorine, and the maximum ds attained was 1.86. Chlorinated disaccharides were found in the hydrolyzates of chlorodeoxycelluloses hydrolyzed under mild conditions, and their structures were studied by mass spectrometry.

Topics: Acetamides; Carbohydrate Sequence; Cellulose; Chloral Hydrate; Chlorides; Lithium; Lithium Chloride; Molecular Sequence Data; Organophosphorus Compounds; Solvents; Succinimides