Cellulose Tosylate Research Articles

Synthesis of soluble cellulose tosylates in an eco-friendly medium

The tosylation of cellulose in the eco-friendly solvent NaOH–urea in the presence of the nonionic surfactant polyethylene glycol alkyl-(C11–C15) ether (Imbentin) yields well soluble p-toluenesulfonic acid esters of cellulose (tosyl cellulose). The influence of reaction time, temperature, and molar ratio on the degree of substitution (DS) was studied. The products were characterized by means of NMR- and FTIR-spectroscopy, elemental analysis and size exclusion chromatography. Moreover, 6-deoxy-6-azido-, 6-deoxy-6-(ω-aminoethyl)amino-, and 6-deoxy-6-thiosulfate cellulose could be prepared by nucleophilic displacement (SN) of the tosyl groups.

Studies on the tosylation of cellulose in mixtures of ionic liquids and a co-solvent

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.

Crosslinked cellulose developed by CuAAC, a route to new materials

This work deals with a novel and simple approach of cellulose reticulation using the Huisgen 1,3-dipolar cycloaddition, also known as a ‘click chemistry’ reaction, catalysed by copper and developed by Sharpless. This reaction is carried out by the addition of a true alkyne and an azide to form a triazole ring connecting the two polysaccharide chains. The addition of two different functions will allow us to control the crosslinking reaction, to avoid intra-chain reactions and thus to promote the creation of an enhanced three-dimensional network. Azidodeoxycellulose was obtained with a DS of 1.5 from tosyl cellulose. The propargylation reaction in aqueous media leading to propargylcellulose with a DS of 1.3. CuAAC reaction was performed between azidodeoxycellulose and propargylcellulose in a DMSO/H2O system using CuSO4, 5H2O/sodium ascorbate as catalytic system. The modified cellulose products were analysed by infrared, NMR and X-ray photoelectron spectroscopies and resulting material was analysed using scanning electron microscopy (SEM).

A study of anhydrocelluloses – Is a cellulose structure with residues in a 1C4-conformation more prone to hydrolysis?

A study of the effect of introduction of 3,6-anhydroglucose residues in the cellulose structure on glycoside hydrolysis rate was performed. A cellotetrose with an 3,6-anhydroglucose as the third residue was synthesised. Acidic hydrolysis of this tetrasaccharide showed that hydrolysis of the 3,6-anhydro-β-D-glucoside linkage was 31.400 times faster than hydrolysis of cellobiose. A series of different 3,6-anhydrocelluloses with different degree of substitution were prepared by tosylation of cellulose with varying amounts of tosyl chloride in dimethylacetamide and subsequent treatment with sodium hydroxide. Anhydrocelluloses with degrees of substitution of 0.02, 0.07, 0.31 and 0.74 were obtained. The anhydrocelluloses were subjected to acidic hydrolysis in 2.0 M aqueous HCl and the rate of hydrolysis monitored by ion chromatography analysis of the amount of glucose and/or cellobiose formed. All 3,6-anhydrocelluloses hydrolyzed with a faster rate than cellulose, but the anhydrocellulose with a low degree of substitution (ds = 0.07) hydrolyzed fastest which was 90 times faster than cellulose.

Unconventional Reactivity of Cellulose Dissolved in Ionic Liquids

AbstractSummary: Ionic Liquids (IL) were applied as solvent and reaction medium in the field of homogeneous cellulose chemistry. Whereas investigations on tosylation and nucleophilic displacement reactions lead to unexpected products the application of the Huisgen reaction was successful. The standard conditions for tosylation of cellulose using the IL 1‐ethyl‐3‐methylimidazolium acetate (EMImAc) as solvent lead exclusively to cellulose acetate, due to activation of the acetate ion of the IL by forming a mixed anhydride with p‐toluenesulfonyl chloride. Further investigations showed that the anions of EMImAc and 1‐ethyl‐3‐methylimidazolium chloride (EMImCl) are able to act as nucleophiles, thus substituting tosyl groups of tosylcellulose and forming unexpected products. Using EMImAc as solvent first to third generation propargyl‐polyamidoamine (PAMAM) dendrons were attached to 6‐azido‐6‐deoxy cellulose (degree of substitution, DS 0.75) utilising the copper catalysed Huisgen reaction leading to novel dendronized cellulose derivatives with DS values of up to 0.60. Detailed structure characterisation of the products, including elemental analysis, FTIR and NMR spectroscopy, indicates that the synthesis approach leads to products without impurities or remaining IL.

Tosylation and acylation of cellulose in 1-allyl-3-methylimidazolium chloride

Tosylation and acylation of cellulose were performed under mild reaction conditions using imidazolium based ionic liquids (ILs) as solvents. The non-degradative nature, lower viscosity, as well as higher solubility of cellulose in [amim]Cl encouraged us to carry out the reactions in this media. The reactions described here were optimised for this particular solvent in order to obtain different cellulose derivatives with high yields, homogeneity and degree of substitution (DS). Two reagents employed for the in situ activation of carboxylic acids were N,N′-carbonyldiimidazole (CDI) and 1-ethyl-3-(3′-dimethylaminopropyl)carbodiimide hydrochloride (EDCI). Final products were characterised by solution and solid-state NMR techniques.

Studies on Non‐natural Deoxyammonium Cellulose

AbstractSummary: Ammonium group containing cellulose derivatives are prepared from homogeneously synthesized cellulose p‐toluenesulfonic acid esters (tosyl cellulose) by conversion with sodium azide and subsequent reduction of the azido moiety applying NaBH4/CoBr2/2,2′‐bipyridine as reagent. Regarding the tosylation, cellulose samples of different degree of polymerization and hemicellulose content possess a different reactivity. The deoxyamino cellulose is water soluble in the protonated state. Elemental analysis, FTIR‐ and NMR spectroscopy were carried out to analyze the degree of substitution and functionalization pattern. It was also studied to synthesize deoxyazido celluloses without isolation of the tosyl cellulose. However, a predominant formation of deoxychloro moieties occurs.

Unconventional cellulose products by fluorination of tosyl cellulose

AbstractThe synthesis of novel deoxy‐fluoro cellulose derivatives obtained by nucleophilic displacement reactions (SN) of p‐toluenesulfonyl (tosyl) cellulose with tetrabutylammonium fluoride (TBAF) is described. Detailed studies concerning the influence of the reaction time and temperature as well as the water content of the TBAF on the composition of the products were carried out. The SN reaction occurs even at room temperature. The degree of substitution of deoxy‐fluoro moieties (DSF) is in the range from 0.22 to 0.47. The polymers contain remaining tosyl groups. Preliminary 19F NMR measurements reveal the presence of the CH2F group. The degradation temperature of the deoxy‐fluoro cellulose derivatives is increased compared to the starting tosyl cellulose, however, a distinct influence of the remaining tosyl groups appears.

Probing the Polarity of Various Cellulose Derivatives with Genuine Solvatochromic Indicators

AbstractKamlet‐Taft's α (hydrogen‐bond donor acidity), β (hydrogen‐bond acceptor basicity) and π* (dipolarity/polarizability) values of carboxymethyl celluloses (CMCs) and cellulose tosylates (CTs) with different degrees of substitution are reported. Fe(phen)2(CN)2 [cis‐dicyanobis(1,10‐phenanthroline)iron(II)] (1), Michler's ketone [4,4′‐bis(N,N‐dimethylamino)benzophenone] (2), and 4‐aminobenzophenone (3) have been used as solvatochromic surface polarity indicators. The three probes 1, 2, and 3, respectively, have been adsorbed onto polymer samples from 1,2‐dichloroethane (1) and cyclohexane (2, 3) solution for the UV/Vis measurements. The probe‐loaded samples have been measured by means of a special reflectance technique. Apparent ET(30) values are calculated by applying linear solvation energy relationships (LSER) using the independently determined α and π* values of the samples according to ET(30) = [ET(30)]0 + aα + sπ*, because ET(30) values are not directly available for these materials. α values of CMCs and CTs significantly decrease with increasing degree of substitution due to the decrease of the number of cellulosic OH groups (Cell‐OH). The dipolarity/polarizability π* values of the CMCs show no linear dependence on the degree of substitution. A slight increase of π* with DS is observed for CTs. The β term using 3 as the probe for CTs is not determinable, because 3 also interacts, via the carbonyl oxygen, with acidic sites of the cellulose OH groups.Formulas of the probe molecules used.magnified imageFormulas of the probe molecules used.

Empirical Polarity Parameters of Celluloses and Related Materials

Kamlet–Taft's α (hydrogen-bond donating (HBD) ability), β (hydrogen-bond accepting (HBA) ability), and π* (dipolarity/polarizability) parameters of native cellulose batches, carboxymethyl celluloses (CMCs), cellulose tosylates (CTs), and other derivatives with different degree of substitution (DS), chitine, amylose, amylopectine, and cellobiose are presented. Fe(phen)2(CN)2 [cis-dicyano-bis-(1,10)-phenanthroline-iron(II), (1)], Michler's ketone [bis-4,4′-(N,N-dimethylamino)benzophenone, (2)], 4-aminobenzophenone (3), coumarine 153 (4), and Reichardt's dye (5) were used as solvatochromic surface polarity indicators. The UV/Vis reflectance spectra of the five surface polarity indicators 1, 2, 3, 4, and 5, adsorbed on the samples from the organic solvents, were measured and the absorption maxima were used to calculate the α, β, π*, and ET(30) values of the polysaccharides surface. α, β, and π* depending on degree of crystallinity of the cellulose samples have been determined. α depends on both amount and strength of accessible acidic surface groups on the cellulose surface. It is significantly larger for crystalline sections than for amorphous parts. The π* scale is suitable for the classification of different cellulose batches, because it seems to be independent of inhomogeneities of the cellulose surface. The α-values of CMCs and CTs significantly decrease with increasing DS inasmuch the number of cellulosic-OH groups (Cell-OH) decreases. A slight increase of π* with DS is observed for CTs.

Regioselective Nitrilotriacetic Acid–Cellulose–Nickel-Complexes for Immobilisation of His6-Tag Proteins

The molecular and supramolecular structural design of cellulose derivatives represents important synthetic and structure analytical aspects of cellulose chemistry. Such tailored cellulose product can be used as substrate for proteins and biocatalysts. New cellulose derivatives, modified with nitrilotriacetic acid (NTA) residues, were synthesised by a nucleophilic substitution reaction starting from cellulose tosylates. These derivatives are able to form clear and thin films on glass surfaces and show remarkable complexation properties concerning nickel(II). The immobilisation of His-tag proteins succeeded on the surface of the transparent cellulose films. The detection of the specific cellulose-protein-binding results from optical measurements of fluorescence effects transmitted by optically marked synthetic proteins designed de novo.

Exclusive and complete introduction of amino groups and their N-sulfo and N-carboxymethyl groups into the 6-position of cellulose without the use of protecting groups

A new regioselective synthesis of 6-amino-6-deoxycellulose with a DS 1.0 (degree of substitution) at C-6, and its 6- N-sulfonated and its 6- N-carboxymethylated derivatives, without using protecting groups is described in this paper. The reaction conditions were optimized for preparing cellulose tosylate with full tosylation at C-6 and partial tosylation at C-2 and C-3. The nucleophilic substitution (S N) reaction of the tosyl group by NaN 3 at low temperature of 50 °C in Me 2SO was achieved completely at C-6, whereas the tosyl groups at C-2 and C-3 were not displaced. In contrast to this, at 100 °C the tosyl groups at C-6, and also those at C-2 and C-3, were replaced by azido groups. This regioselective reaction that depends on temperature makes it possible to reach a selective and quantitative S N reaction at C-6 at low temperatures. In the subsequent reduction step with LiAlH 4, the azido group at C-6 was reduced to the amino group, and the tosyl groups at C-2 and C-3 were simultaneously completely removed. Also reported is a temperature-dependent, regioselective and complete iodination by nucleophilic substitution of the tosyl group at C-6 at 60 °C. At higher temperatures from 75 to 130 °C, substitution is also observed to occur at C-2. The selective iodination at 60 °C was employed to confirm the complete tosylation at C-6 of cellulose. The reaction products were identified by four different independent quantitative methods, namely 13C NMR, elemental analysis, ESCA, and fluorescence spectroscopy. 6- N-Sulfonated and 6- N-carboxymethylated cellulose derivatives were also synthesized. The new derivatives are potent candidates for structure–function studies, e.g., studies in relation to regioselectively 2- N-sulfonated and 2- N-carboxymethylated chitosan derivatives.

Influence of the p-toluenesulphonylation of cellulose on the polymer dynamics investigated by dielectric spectroscopy

Cellulose p-toluenesulphonates (tosyl cellulose) were studied by dielectric spectroscopy. Two relaxation processes were observed for samples of low degrees of substitution (DS) in the low temperature range (−130 to 0 °C). These are related to the local chain and the tosyl substituent motion, β- and γ-relaxations, respectively. For DS values higher than 1.4, the dielectric spectra no longer could be separated into the individual processes, because the dielectric response became reduced in intensity and its distribution in the frequency scale was broadened by cross-correlation of different motions between the modes of the substituents and the segmental motions of the chain. Significantly, different local chain (β-relaxation) behaviour was found for derivatives of DS≈0.9 with block-like and random distribution of substituents along the backbone. The dynamic behaviour of the tosylated polymers is compared with other cellulose derivatives and revealed similar qualitative behaviour, but the type of the substituents at the anhydroglucose unit has a characteristic influence on the dynamic parameters of the relaxation time, the activation energy related and the shape parameter of the relaxation processes.

Nucleophilic displacement reactions on tosyl cellulose by chiral amines

New 6-deoxy-6-amino cellulose derivatives with a degree of substitution (DS) in the range from 0.4 to 0.6 were synthesized by nucleophilic displacement (SN) reactions of cellulose tosylates (DSTos 0.74 and 1.29) with R(+)-, S(−)- and racemic 1-phenylethylamine under homogeneous conditions in N,N-dimethylformamide and water. The structure of the polymers was characterized by elemental analysis, FTIR and 13C NMR spectroscopy. The DS values obtained as well as the optical rotation and circular dichroism measurements in dimethyl sulfoxide reveal that the initial chirality of the cellulose backbone does not have any significant influence on its reactivity with either of the two enantiomeric amines.

A novel soluble aminocellulose derivative type: its transparent film-forming properties and its efficient coupling with enzyme proteins for biosensors

By means of the reaction of 6-tosylcellulose derivatives with diamino compounds, it has been possible to provide a new soluble and film-forming aminocellulose-derivative type with a diamine residue at C-6 of the anhydroglucose unit (AGU) and with so-called solubilizing groups, such as acetate, benzoate, carbanilate, methoxy and/or tosylate groups at C-2/C-3. For example, aminocellulose derivatives were synthesized with aliphatic diamine residues of different alkyl chain lengths ((CH2)m with m = 2, 4, 6, 8, 12) at C-6. Other new aminocellulose derivatives were those with an aromatic diamine residue, e.g., 1,4-phenylenediamine or benzidine residue and others, at C-6. Depending on the structure of the diamine residue at C-6 and of the substituents at C-2/C-3, the aminocellulose derivatives were soluble in various solvents, mostly in N,N-dimethylacetamide (DMA) or dimethylsulfoxide (DMSO). Aminocelluloses with a diaminoethane or diaminobutane residue at C-6 and methoxy groups at C-2/C-3 were soluble in water. All the amino celluloses synthesized formed transparent films from their solutions. These aminocelluloses apparently form superstructures or so-called supramolecular architectures according to a structure-inherent organization principle, which became visible, for example, in the case of PDA cellulose tosylates (in DMA) as gel-like aggregates after approx. 1 week of storage at 4°C. The superstructures or aggregates could be imaged on the aminocellulose film surface by atomic force microscopy (AFM) in the form of characteristic topographic structures, e. g. as “hole” structures. In this way, structural and environment-induced factors influencing the aggregate formation were found. The transparent aminocellulose films were excellently suited for covalent coupling with oxidoreductase enzymes such as glucose oxidase (GOD), lactate oxidase (LOD), peroxidase (POD) via bifunctional compounds. A number of new bifunctional enzyme coupling reactions, e. g. via L-ascorbic acid or benzenedisulfonic dichlorides forming amide or sulfonamide coupling structures led to functionally stable nanostructure building blocks with recognition patterns in the case of GOD and POD coupling to PDA cellulose tosylate films. The PDA cellulose derivatives proved to be promising cellulose structural units because the redox-chromogenic PDA residue at C-6 provides the derivatives with a wide range of reaction possibilities, e.g. diazo coupling reactions, NH2-reactive coupling reactions and oxidative coupling reactions to redox dyes.

Thermal studies on homogeneously synthesized cellulosep-toluenesulfonates

The thermal behavior in argon of homogeneously synthesized cellulose p-toluenesulfonates (tosylates) with a degree of substitution (DS) ranging from 0.4 to 2.3 was studied by means of thermogravimetry and derivative thermogravimetry from ambient temperature up to 500°C. For comparison, the thermal behavior of the starting celluloses used (pulps, linters, bacterial cellulose) was also examined. The thermal degradation of cellulose tosylates was initiated at lower temperature than cellulose itself and proceeds in two main stages. The temperature of the first one (169 196°C) increases with increasing DS and is independent of the molecular weight. Activation energies calculated following the method of Broido, FTIR, and ultimate analysis as well as mass spectroscopy show that the first stage of degradation is closely associated not only with the scission of tosyl ester groups but also with a partially degradation of the polymer backbone. Further, the temperature-concen-tration diagram for the system cellulose tosylate 20/o-dichlorobenzene was studied by optical observations and calorimetric investigations. A liquid-liquid demixing interferes with the glass transition of the cellulose tosylate-solvent system. It results in the solidification of the solution. © 1996 John Wiley & Sons, Inc.

Homogeneous synthesis of cellulose p‐toluenesulfonates in N,N‐dimethylacetamide/LiCl solvent system

AbstractPure cellulose p‐toluenesulfonates (tosylates) with an insignificant formation of chlorodeoxy groups were prepared by reacting cellulose dissolved in a solution of N,N‐dimethylacetamide and LiCI with tosylchloride (Tos‐CI) in the presence of triethylamine within 24 h at 8°C. Various cellulosic starting materials with a degree of polymerization from 280 to 5 100 were used. The samples obtained were characterized by means of elemental analysis, FTIR and 13C NMR spectroscopy, and their intrinsic viscosities. The rise of the molar ratio of Tos‐CI/anhydroglucose unit (AGU) from 0.6 to 9.0 leads to an increase in the degree of substitution (DS) from 0.4 up to a maximum value of 2.3. The cellulose tosylates are readily soluble in common organic solvents like dimethyl sulfoxide (within the whole DS range) and in N,N‐dimethylacetamide, N,N‐dimethylformamide, acetone, tetrahydrofuran and trichloromethane depending on DS. As revealed by 13C NMR spectroscopy a faster tosylation takes place at the O‐6 atom of AGU compared with the O‐2/3 atoms. This was additionally confirmed by analysis of the corresponding iododeoxy celluloses synthesized with NaI in acetylacetone. Furthermore, some important properties as stability against alkaline and heat were studied as well.

Preparation and Identification of Sodium Deoxycellulosesulfonate.

A new cellulose derivative, sodium deoxycellulosesulfonate was prepared by a nucleophilic substitution of cellulose p-toluenesulfonate (cellulose tosylate) with sodium hydrogensulfite under refluxing in water. Degree of substitution of water-insoluble fraction of the sulfonate increased with reaction time and it was about 0.10 for cellulose tosylate with DS of 0.92 and 0.065 for that with DS of 0.79 at 24h, respectively. Yield of the insoluble sulfonates decreased with reaction time and showed a value as low as 48mol% for cellulose tosylate with DS of 0.92 at 48h. Conversions of the p-toluenesulfonate group to the sulfonate group were 11 and 8.2mol% for cellulose tosylates with DS of 0.92 and 0.79 at 24h, respectively, and p-toluenesulfonate group still remained even after the reaction of 48h. The sodium deoxycellulosesulfonate was identified by dyeing test with Methylene Blue for acid group, micro combustion test for sulfur, incineration test for sulfonate and sulfate groups, and hydrolysis-in-cineration test for sulfonate group, as well as with IR absorption spectra.

Cationic Graft Polymerization of 2-Oxazolines on Cellulose Derivatives

Cationic graft polymerization of 2-oxazolines on cellulose derivatives such as chlorinated cellulose (Cell-Cl), cellulose acetate halogenacetate (AcCell-AcX), and cellulose tosylate (Cell-OTs) was investigated. With Cell-Cl the successful graft polymerization of 2-methyl-2-oxazoline (MeOXZ) required the presence of potassium salt but with AcCell-AcX and Cell-OTs it proceeded without the salt. The reactivity of halogens in graft polymerization of MeOXZ on halogenated cellulose derivatives increased in the order of I−> Br−> Cl−. This is explained by the nucleophilicity of halogen ions compared with that of MeOXZ. Graft copolymers prepared with AcCell-AcX were hydrolyzed by 0.5 N NaOH solution to isolate the branched poly(MeOXZ). The molecular weight of the branched poly(MeOXZ) measured by GPC was in the range of 380 to 3510 depending on the reaction conditions. 2-Oxazoline (OXZ) did not graft-polymerize with halogenated cellulose derivatives, but graft-polymerized with Cell-OTs.

Thermal properties of tritylated and tosylated cellulose

AbstractTriphenylchloromethane and p‐toluenesulfonyl chloride were reacted with chopped or powdered cellulose, with and without premercerization, to form trityl–cellulose ethers or tosyl–cellulose esters. Powdered and premercerized cellulose samples were more readily derivatized. Differential scanning calorimetric (DSC) and thermogravimetric (TG) analyses were performed in nitrogen on these derivatives. DSC and TG thermograms were affected by the particular derivative and the degree of substitution. The decomposition temperatures for both derivatives were lower than for the unmodified cellulose. Trityl cleavage may have been detected by DSC as a broad endothermic area showing no weight loss that preceded the major endothermic decomposition peak. Decomposition temperatures were lowered, but not sufficiently to prevent decomposition products from being combustible. No increase in residue was effected. Thermal decomposition of tosyl–cellulose was substantially different from that of the trityl derivative. As the degree of tosyl substitution increased, decomposition occurred at lower temperatures as an increasing exotherm. Tosyl derivatives all produced high residues. These changes in thermal characteristics were indicative of increased flame resistance. Oxygen index (OI) values relate to flame resistance and show that tritylation was detrimental to the cellulose and that tosylation imparted some degree of flame resistance.