Synthesis of Carboxymethyl Cellulose Based on Short Fibers and Lignified Part of Flax Pedicels (Boon)

The conditions under which carboxymethyl ethers of cellulose with various degrees of substitution can be prepared from wastes formed in production of flax fibers were studied. The structure of the cellulose ethers synthesized was studied by IR Fourier spectroscopy and physicochemical methods.     

氮杂冠醚研究Ⅺ．叔胺型氮杂冠醚的合成

１１种酰胺型氮杂冠醚用ＬｉＡｌＨ４－ＴＨＦ体系还原，高收率地合成了新的叔胺型氮杂冠醚；通过２，３－苯并－１０－氮杂－１，４，７，１３－四氧杂环十五－２－烯与丙烯腈进行氰乙基化反应，同样制得了一种新的叔胺型氮杂冠醚。１２种新化合物的结构均经元素分析、ＩＲ、１ＨＮＭＲ和ＭＳ所证实。讨论了这类氮杂冠醚的质谱裂解过程     

Characterization of Water-Soluble Cellulose Derivatives in Terms of the Molar Mass and Particle Size as well as Their Distribution

The property profile of cellulose derivatives dissolved in aqueous solvents is not only dependent on the chemical composition (average-, molar- or regiospecific degree of substitution, as well as the substitution along the chain), solvent, temperature and concentration but also on the molar mass and the particle size. All this information can be obtained from the Mark-Houwink-Sakurada-relationship ([;gh]-M-) or the R_G-M-relationship, if these are at hand. These relationships are suitable for a specific degree of substitution. The R_G-M-relationship has only been determined and published for a few water-soluble cellulose derivatives. The prerequisite is the availability of a homologous series of samples with the same chemical composition. In this paper it is shown that only the ultrasonic degradation is able to create such a series. Due to the ability of coupled methods of analysis to acquiring absolute data, molar mass and particle size distributions have been compiled in recent years. Using such methods it was possible to determine molar mass and particle size distributions of several aqueous cellulose derivative solutions by combining a fractionation unit (size exclusion chromatography (SEC) or flow field-flow fractionation (FFFF)) with multi angle laser light scattering (MALLS) for the detection of Mw and R_G and concentration detection (DRI). Results for nonionic cellulose ethers, mixed cellulose ethers, ionic carboxymethyl cellulose, sulfoethyl cellulose, hydrophobically modified hydroxyethyl cellulose were obtained and are partially discussed with focus on the recovery of cellulose derivates after fractionation and the impact on the distribution functions.     

Carbonization of some cellulose ethers and their graft copolymers with polyacrylonitrile

Low-temperature carbonization of hydroxyethyl, allyloxyethyl, and allylcarboxymethyl cellulose ethers and their copolymers with polyacrylonitrile was studied. The quantitative relationships between the degree of carbonization, on the one hand, and the degree of substitution of cellulose hydroxy groups and chemical structure of the substituents, on the other, were established. The dependence of the carbon residue on the amount of grafted polyacrylonitrile chains tends to a certain limit. The carbon residue depends on the atmosphere in which the carbonization is performed.Translated from Zhurnal Prikladnoi Khimii, Vol. 77, No. 8, 2004, pp. 1366–1369.Original Russian Text Copyright © 2004 by Sazanov, Nudga, Petrova, Novoselova, Ugolkov, Fedorova, Kulikova, Gribanov.     

Electron capture negative ion and positive ion chemical ionization mass spectrometry of polychlorinated phenoxyanisoles

Several polychlorinated phenoxyphenols with three to nine chlorine atoms were examined as their methyl ethers by electron capture negative ion and positive ion chemical ionization and electron impact mass spectrometry. In chemical ionization studies methane, hydrogen, nitrogen, helium and argon were used as reagent gases. Selected compounds were also examined with deuteriomethane, ammonia and deuterioammonia as reagent gases. Utilization of chemical ionization spectra in conjuction with electron impact spectra provides substantial structural information about these compounds. Chemical ionization spectra provide information about chlorine atom substitution. The position of phenoxy substitution can be established from electron capture negative ion and positive ion spectra.     

Hydrogen bonds in regioselectively substituted cellulose derivatives

Formation of hydrogen bonds in various cellulose derivatives, 2,3-di-O- and 6-O-substituted cellulose ethers, were characterized by FTIR and solid-state CP/MAS¹³C-NMR. The polymers were synthesized by regioselective substitution of hydroxyl groups and had a uniform structure. Since their three hydroxyl groups (OH) are selectively blocked, the cellulose derivatives appeared to form specific inter- and intramolecular hydrogen bonds. The characteristic OH stretching frequencies in IR spectra and the C-1 chemical shift in CP/MAS spectra of 6-O-substituted cellulose derivatives indicated existence of two equivalent intramolecular hydrogen bonds between ether oxygen and OH groups at 3-OH-O5′ and O6-HO-2′ [Figure 3(C)]. Influence of the substituents at the C-6 position on the formation was not significant except trityl group. Behavior of the hydrogen bonds in 6-O-tritylcellulose were also discussed. © 1994 John Wiley & Sons, Inc.     

Preparation of mixed cellulose ethers by the reaction of short flax fibers and cotton linter with monochloroacetamide

The conditions of preparation of mixed cellulose ethers containing carboxy and amino groups by the reaction of samples of short flax fiber and cotton linter with monochloroacetamide were examined. The influence of the amino groups of the mixed cellulose ethers on the rheological properties of their aqueous solutions was elucidated.     

Preparation,characterization, and mesophase formation of esters of ethylcellulose and methylcellulose

A range of mixed ether-esters of cellulose was prepared from partially substituted ethylcellulose and methylcellulose. The ¹³C-NMR analysis of ethylcellulose with a DS of 2.5 indicated that the hydroxyl groups at carbon six of anhydroglucose units were completely substituted. Acetylation of the ethylcellulose under different conditions yielded (acetyl) (ethyl) cellulose (AEC) samples with acetyl degree of substitution ranging from 0 to 0.5. Fully substituted (propionyl) (ethyl) cellulose (PEC) and (acetyl) (methyl) cellulose (AMC) were also prepared. Chiral nematic liquid crystals were formed in these mixed ester/ethers of cellulose in concentrated solutions of acidic solvents. The critical concentration for the phase separation of the cellulosic solutions depended on the nature of the substituent, the degree of substitution, and the solvent at a given temperature. Methylcellulose solutions in trifluoroacetic acid and dichloroacetic acid form chiral nematic liquid crystals with a left-handed helicoidal structure. The acetylated methyl cellulose samples did not show the reversal of handedness with increasing acetyl content that was previously observed for the corresponding ethylcellulose samples. © 1994 John Wiley & Sons, Inc.     

Preparation of mixed ethers by reaction of carboxymethyl cellulose with urea and their physicochemical properties

The conditions of preparation of mixed cellulose ethers containing carboxymethyl and amide groups by reaction with urea were examined with samples of commercial carboxymethyl cellulose and that prepared from flax cellulose as examples. The water solubility of the resulting products and their sorption activity toward copper ions were examined in relation to the amount of amide groups introduced.     

Interactions of ionic liquids with polysaccharides 9. Hydroxyalkylation of cellulose without additional inorganic bases

Water-soluble hydroxyalkyl cellulose with a molar degree of substitution of up to 2.79 was prepared under completely homogeneous reaction conditions in various ionic liquids without addition of inorganic bases. In acetate containing solvents the IL acts as a catalyst. The substitution patterns of the cellulose ethers were analyzed by ¹³C NMR spectroscopy, ¹H NMR spectroscopy after peracetylation and GLC/MS after permethylation and depolymerization. A diminished tendency towards the formation of side chains compared to heterogeneously prepared hydroxyalkyl celluloses in the presence of inorganic bases was found.     

Silylation of Cellulose and Starch – Selectivity, Structure Analysis, and Subsequent Reactions

The silylation of cellulose and starch under different starting conditions is reviewed. The control of the degree of substitution (DS) and regioselectivity in dependence of the reaction pathway are discussed in detail. The synthesis of trimethylsilyl cellulose (TMSC) in the system hexamethyldisilazane (HMDS)/ammonia leads to partially and completely silylated products controlled by the amount of the components. Hydrolytic desilylation of TMSC in tetrahydrofuran (THF)/ammonia gives the partially desilylated products. The desilylation proceeds statistically along the polymer chains. The reaction of cellulose dissolved in N,N-dimethylacetamide (DMA)/LiCl with bulky thexyldimethylchlorosilane (TDSCl) in the presence of imidazole leads to 2,6-di-O-TDS cellulose. The silylation of starch dissolved in dimethylsulfoxide (DMSO) with TDSCl/pyridine results in the formation of regioselectively 2-O and 6-O functionalized silyl ethers with DS values up to 1.8. 6-O Silyl ethers of cellulose and starch were synthesized with TDSCl highly activated in the reaction system N-methylpyrrolidone (NMP)/ammonia. Two- dimensional NMR techniques after subsequent modifications of the remaining OH groups have been established as important methods for the characterization of the substitution pattern of the described silyl ethers. In the case of starch, the distribution of the substituents could be detected not only in the anhydroglucose units (AGU) but also in the non-reducing end groups (NEG).     

Hot Topics in Polysaccharide Chemistry – Selected Examples

Summary: The paper highlights recent developments in polysaccharide chemistry. Cellulose tert-butyl- and thexyldimethylsilyl ethers with degree of substitution up to 2 were accessible and comprehensively characterized by means of NMR spectroscopy. These derivatives enable the preparation of 3-O-functionalized cellulose ethers. Especially the allyl ether as protecting group at position 3 can be used for the synthesis of 2,6-di-O-methyl cellulose. Nucleophilic displacement reactions of cellulose p-toluenesulfonic acid esters with amines afforded deoxyamino celluloses that form stable monolayers on different substrates. Based on 6-deoxy-6-azido cellulose, dendrons with a focal alkyne moiety were bound via the copper(I) catalyzed Huisgen reaction. Moreover, dextran derivatives were synthesized that form stable nanoparticles useful, e.g., for the determination of the pH value in biological systems.     

Variation of the reactivity of flax fiber cellulose in the course of flax ripening

Carboxymethyl cellulose ethers were prepared from flax fibers of various degrees of ripeness. The influence exerted by the degree of ripeness of flax fibers on their reactivity in carboxymethylation was examined. The rheological properties of aqueous solutions of the synthesized carboxymethyl cellulose were studied.     

Studies on the synthesis of 2,3-o-hydroxyalkyl ethers of cellulose

Novel 2,3-O-hydroxyethyl- and 2,3-O-hydroxypropyl cellulose products were synthesized by heterogeneous etherification of 6-O-(4-monomethoxytrityl) cellulose (MMTC). Due to the very hydrophobic character of MMTC, the reaction was successful in the presence of anionic and non-ionic detergent in the reaction mixture yielding the 2,3-O-cellulose ethers with a molar degree of substitution (MS) varying between 0.25 and 2.00 after detritylation. The products were characterized by means of (1)H and (13)C NMR spectroscopy including two-dimensional methods. The 2,3-O-hydroxypropyl cellulose samples are soluble in water at a MS as low as 0.8. The spectroscopic studies showed that the unusual solubility results from a preferred substitution of hydroxy groups of the anhydroglucose unit while the newly formed hydroxy moieties are included in the reaction to a minor extent only. In contrast, conventionally synthesized hydroxypropyl cellulose is soluble in water starting at a MS of about 4.0 because of the formation of oxyethylene side chains. (13)C DEPT 135 NMR spectrum of 2,3-O-hydroxypropyl cellulose.     

The synthesis and thermotropic behaviour of an ethyl cellulose derivative containing azobenzene-based mesogenic moieties

An ethyl cellulose derivative containing azobenzene-based mesogenic moieties was prepared by the reaction of 4-methoxyazobenzene-4'-oxyacetic acid and ethyl cellulose by esterification in the presence of N,N' -dicylcohexylcarbodiimide and 4-dimethylaminopyridine. Its chemical structure and liquid crystalline properties were characterized by FTIR, 1 H NMR, POM, DSC and WAXD. The degree of substitution of the cellulose backbone by the azobenzene-based mesogenic moieties is 0.9. The polymer is thermotropic and exhibits liquid crystalline behaviour over the temperature range 125-172°C.     

Cellulose: fascinating biopolymer and sustainable raw material

As the most important skeletal component in plants, the polysaccharide cellulose is an almost inexhaustible polymeric raw material with fascinating structure and properties. Formed by the repeated connection of D-glucose building blocks, the highly functionalized, linear stiff-chain homopolymer is characterized by its hydrophilicity, chirality, biodegradability, broad chemical modifying capacity, and its formation of versatile semicrystalline fiber morphologies. In view of the considerable increase in interdisciplinary cellulose research and product development over the past decade worldwide, this paper assembles the current knowledge in the structure and chemistry of cellulose, and in the development of innovative cellulose esters and ethers for coatings, films, membranes, building materials, drilling techniques, pharmaceuticals, and foodstuffs. New frontiers, including environmentally friendly cellulose fiber technologies, bacterial cellulose biomaterials, and in-vitro syntheses of cellulose are highlighted together with future aims, strategies, and perspectives of cellulose research and its applications.     

Dynamic mechanical investigations of different substituted cellulose o-silyl ethers

In contrast to many cellulose derivatives, the cellulose O-silyl ethers with bulky side groups exhibit scarcely a change in glass transition temperature by a variation of the degree of substitution (DS) or degree of polymerization (DP) or by introducing phenyl carbamate groups for the remaining hydroxyls along the main chain. However, a substitution of these hydroxyls by flexible acetate groups lowers the glass transition temperature considerably. The secondary dispersion (relaxation) behavior is strongly influenced by the various substituents and can be correlated to specific motions of the molecules. The dynamic mechanical properties are also dependent on the kind of preconditioning of the samples.     

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.     

Enthalpies of interaction between cellobiose and the derivatives of cellulose in aqueous solutions

The enthalpy of interaction between cellobiose and sodium carboxymethyl cellulose, methyl cellulose, and 2-hydroxyethyl cellulose in water is determined. The exothermal nature of the interaction between cellulose and cellulose ethers is established. The strongest intermolecular interaction is found between cellobiose and 2-hydroxyethyl cellulose. The results are discussed in the context of the polysaccharide molecular structure.     

Influences of chemical modifications on the mechanical strength of cellulose beads

Spherical cellulose beads having narrow particle-size distribution were prepared by the coagulation/regeneration method for small viscose droplets formed by centrifugal force in an acid bath. The influences of chemical modifications on mechanical strengths such as the hydraulic property and compressive strength were investigated, together with the effects on crystallinity, particle size and degree of swelling. Cross-linking with epichlorohydrin and substitution of hydroxyl groups in cellulose with diethylaminoethyl, carboxymethyl and cyanoethyl groups were studied. No remarkable differences were found in X-ray diffraction patterns for the cellulose beads after the chemical modification. The substitution promoted swelling of the beads and decreased the mechanical strength, probably by scission of intermolecular and/or intramolecular hydrogen bonds in cellulose. However, the cross-linking retarded the cellulose beads from swelling effectively. The beads were made significantly ha rder by the substitution, and this hardening effect competed with the softening effect of the swelling. Moreover, it was suggested that the simple compression test was useful for the prediction of the hydraulic property of the cellulose beads in the column operation. 0969--0239 © 1998 Blackie Academic & Professional