Synthesis and properties of carboxymethyl cellulose‐graft‐poly(acrylic acid‐co‐acrylamide) as a novel cellulose‐based superabsorbent

A new cellulose‐based superabsorbent polymer, carboxymethyl cellulose‐graft‐poly(acrylic acid‐co‐acrylamide), was prepared by the free‐radical grafting solution polymerization of acrylic acid (AA) and acrylamide (AM) monomers onto carboxymethyl cellulose (CMC) in the presence of N,N′‐methylenebisacrylamide as a crosslinker with a redox couple of potassium persulfate and sodium metabisulfite as an initiator. The influences of reaction variables such as the initiator content, crosslinker content, bath temperature, molar ratio of AA to AM, and weight ratio of the monomers to CMC on the water absorbency of the carboxymethylcellulose‐graft‐poly(acrylic acid‐co‐acrylamide) copolymer were investigated. The copolymer's structures were characterized with Fourier transform infrared spectroscopy. The optimum reaction conditions were obtained as follows: the bath temperature was 50°C; the molar ratio of AA to AM was 3 : 1; the mass ratio of the monomers to CMC was 4 : 1; and the weight percentages of the crosslinker and initiator with respect to the monomers were 0.75 and 1%, respectively. The maximum water absorbency of the optimized product was 920 g/g for distilled water and 85 g/g for a 0.9 wt % aqueous NaCl solution. In addition, the superabsorbent possessed good water retention and salt resistance. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 1382–1388, 2007     

Surprising Insensitivity of Homogeneous Acetylation of Cellulose Dissolved in Triethyl(n‐octyl)ammonium Chloride/Molecular Solvent on the Solvent Polarity

The homogeneous acetylation of microcrystalline cellulose (MCC) by acetyl chloride and acetic anhydride in triethyl(n‐octyl)ammonium chloride (N₂₂₂₈Cl)/molecular solvents (MSs) is investigated. The reaction with both acylating agents shows the expected increase of the degree of substitution (DS) on reaction temperature and time. Under comparable reaction conditions, however, DS is surprisingly little dependent on the MS employed, although the MSs differ in empirical polarity by 7 kcal mol^?1 as calculated by use of solvatochromic probes. The empirical polarities of (MCC + N₂₂₂₈Cl + MS) differ only by 0.8 kcal mol^?1. The formation a polar electrolyte sheath around cellulose chains presumably contributes to this “leveling‐off” of the dependence DS on the polarity of the parent MS employed. N₂₂₂₈Cl recovery and recycling is feasible.     

Comparison of succinylation methods for bacterial cellulose and adsorption capacities of bacterial cellulose derivatives for Cu<Superscript>2+</Superscript> ion

Bacterial cellulose (BC) was homogenously modified with succinic anhydride in N,N-dimethylacetamide/LiCl in the presence of triethylamine and heterogeneously in pyridine in the presence of 4-dimethylaminopyridine. FTIR, XRD, 13C CP MAS NMR, SEM were used to characterize BC and succinylated bacterial cellulose (SBC). For homogeneous modification, the degree of substitution (DS) of SBC differs from 0.21 to 1.45 with the variation of the adding amount of succinic anhydrate, temperature, reaction time, and the amount of triethylamine. DS and XRD profiles reveal that heterogenous reaction mainly happens on the surface of BC membrane. The adsorption capacity and mechanism of Cu²⁺ onto BC and SBC were investigated. The result shows the adsorption is affected by the morphology and the DS of adsorbents.     

Carboxymethylation of cellulosic material (average degree of polymerization 2600) isolated from cotton (Gossypium) linters with respect to degree of substitution and rheological behavior

Carboxymethylation of cellulosic material (average degree of polymerization 2600) containing 76.5% cellulose and 23.6% xylose isolated from cotton (Gossypium) linters was studied under varying reaction conditions with respect to maximum degree of substitution (DS). The influence of reaction conditions on the apparent viscosity of the prepared derivatives was also studied. The conditions optimized were sodium hydroxide concentration 3.75M, monochloroacetic acid concentration 2.05 mol/AGU, carboxymethylation time 3.5 h, and temperature 55°C, to yield carboxymethyl cellulose of DS 0.77. Rheological studies of 1 and 2% solutions of the optimized product revealed their non‐Newtonian pseudoplastic behavior. Repeating units of the optimized product were also determined by HPLC after complete depolymerization of the polymer. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 96: 1477–1482, 2005     

Synthesis and Characterization of Cellulose Carbamates Having α-Amino Acid Moieties

Summary The reaction of cellulose with N-carbonyl α-amino acid ester 1 leading to cellulose carbamate 2 was carried out in N,N-dimethylacetamide at 100 °C. For N-carbonyl L-leucine ethyl ester (1a), the degree of the carbamate substituent (DS) in 2a was 2.5 for [1a]/[glucose units in cellulose] = 3.0 and reached ca. 3.0 for [1a]/[glucose units in cellulose] = 4.0. Cellulose carbamate 2a was highly soluble in not only aprotic polar solvents but also other organic solvents such as ethyl ether and methyl alcohol. The chiral discrimination ability of 2a was higher than those of the cellulose carbamates having L-phenylalanine and L-aspartic acid moieties.     

Synthesis and property studies of N‐carboxymethyl chitosan

N‐carboxymethyl chitosans (N‐CMC) were synthesized from chitosan in water with chloroacetic acid instead of comparatively expensive glyoxylic acid. The optimal reaction conditions were 90°C and 4 h with a ratio of chloroacetic acid to chitosan 5 : 1(w/w). The degree of substitution of product exceeded 1.32. The N‐carboxymethyl chitosans were characterized by XRD, FTIR, ¹H‐NMR, and the water solubility and isoelectric point of N‐CMC with different degrees of substitution were determined. FTIR and ¹H‐NMR data has confirmed that the substitution reaction occurred on the amino groups. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Nucleophilic displacement reactions on tosyl cellulose by chiral amines

Summary 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 (S_N) reactions of cellulose tosylates (DS_Tos 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. Received: 21 September 2000/Accepted: 5 January 2001     

Homogenous carboxymethylation of cellulose in the NaOH/urea aqueous solution

In this work, the carboxymethylation of cellulose in the alkaline cellulose solvent, 7 wt% NaOH/12 wt% urea aqueous solution, was investigated. Carboxymethyl cellulose (CMC) samples were characterized with FT-IR, NMR, HPLC, and viscosity measurements. Water-soluble CMC with DS = 0.20–0.62 was prepared from both Avicel cellulose and cotton linters. Thus, carboxymethylation of cellulose in NaOH/urea leads to a polymer with the lowest DS value for water solubility (0.20) of CMC known. The total DS of CMC could be controlled by varying the molar ratio of reagents and NaOH to AGU and the reaction temperature. Structure analysis by means of HPLC after complete depolymerization showed that the mole fractions of the different carboxymethylated repeating units as well as those of unmodified glucose follow the simple statistic pattern. A distribution of the carboxymethyl groups at the level of the AGU in the order O-6 > O-2 > O-3 was determined. The results were similar with findings for CMC obtained by totally homogeneous reaction of cellulose in aqueous solvents such as Ni[tris(2-aminoethyl)amine](OH)₂.     

Rapid homogeneous esterification of cellulose extracted from Posidonia induced by microwave irradiation

In this article, we report on the synthesis of cellulose esters by the reaction of cellulose and some cyclic anhydrides, such as succinic, maleic, and phthalic anhydrides. For this, an esterification method was finalized. Indeed, cellulose extracted from Posidonia biomass was first solubilized in the solvent system lithium chloride (LiCl)/N,N‐dimethylacetamide and then esterified by cyclic anhydride in the presence of catalysts such as N,N‐dimethyl‐4‐aminopyridine, tripropylamine, tributylamine, and calcium carbonate. This method was fast and reproducible with the LiCl system as a solvent and with an efficient activation by controlled microwave power. In this way, the reaction time was reduced from several hours to just a few minutes. The reaction products were characterized by IR and solid‐state cross‐polarization/magic angle spinning ¹³C‐NMR spectroscopy. The degree of substitution (DS) and the grafted ester group content of the different products were obtained by alkali saponification followed by titration of the excess alkali. Two activation methods were compared, and the results show that the application of classical heating gave less successful results than those obtained by microwave activation. Indeed, with microwave activation, a higher DS (2.25) was obtained after 10 min. However, with classical heating, a value of DS equal to 1.2 was obtained after 12 h. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Water-absorbing characteristics of acrylic acid-grafted carboxymethyl cellulose synthesized by photografting

Cellulosic absorbents for water were synthesized by photografting (λ > 300 nm) acrylic acid (AA) onto fiberous carboxymethyl cellulose (CMC, degree of substitution [DS] = 0.1–0.4) at 30°C in the presence of N,N′-methylenebisacrylamide as a crosslinker. The CMC sample was pretreated with hydrogen peroxide in the presence of sulfuric acid to prepare CMC peroxides with a peracid type as a polymeric photoinitiator. The peroxides were active for the photografting and AA could be grafted onto CMC with percent graftings higher than 150% by photoirradiation of 10 min at 30°C. The amount of water absorbed increased with increasing percent grafting of AA and DS of CMC. The amount was reduced considerably when the absorbents were prepared by the photografting of AA onto crosslinked CMC in the absence of the crosslinker. Graft copolymers which display a decreasing water absorbency as a function of temperature were prepared by two methods: In the first synthesis method, AA and N-isopropylacrylamide (NIPAAm) binary monomers were graft-copoly-merized onto CMC samples using photoinitiation. In the second method, photografting of AA was followed by a second-step photografting of NIPAAm to produce a terpolymer with two types of side chains of differing repeat unit composition on the CMC substrate. Graft copolymers formed by both methods showed decreasing water absorbency as temperature increased with losses in water absorbency of up to about 60% as the temperature was increased above 30°C. Effects of NIPAAm composition and corsslinker content in the graft copolymers on the decreasing water absorbency as a function of temperature were also examined. © 1996 John Wiley & Sons, Inc.     

Preparation, characterization and antimicrobial activity of quaternized carboxymethyl chitosan and application as pulp-cap

Quaternized carboxymethyl chitosan (QCMC) was prepared from which carboxymethyl chitosan (CMC) was prepared from chitosan first, then N-quaternary ammonium group was introduced by the reaction of CMC with 2, 3-epoxypropyl trimethylammonium. The structures of the derivatives were characterized by FT-IR, XRD, ¹³C NMR, ¹H NMR and gel permeation chromatography. In vitro antimicrobial activities of QCMC were evaluated against Escherichia coli, which is a Gram-negative bacterium, and Staphylococcus aureus, which is a Gram-positive bacterium. In compared with carboxymethyl chitosan (CMC) and quarternary chitosan (QC) of the same degree of substitusion (DS), we found that QCMC has stronger antimicrobial activity. Then we went deep into study of the relationship between their structure and antimicrobial activity, found that the DS of CMC do little effect to their antimicrobial activity, but as the increase of their DS of quaternization or the decrease of their molecular weight, the antimicrobial activity of QCMC become stronger. QCMC was complexed with calcium hydroxide as pulp-cap. Animal experiment results indicated that QCMC can strongly induce reparative dentine formation and showed a better ability in dentin inducing compared with calcium hydroxide.     

Synthesis,characterization, and anticoagulant activity of carboxymethyl starch sulfates

To develop a renewable and compatible anticoagulant as potential heparin alternative, carboxymethyl starch sulfate (CMSS) was prepared by the reaction of carboxymethyl starch (CMS) and sulfating reagent [N(SO₃Na)₃]. The chemical structures of CMS and CMSS were characterized by Fourier transform infrared spectroscopy and ¹³C nuclear magnetic resonance. The influences of reaction parameters, including the pH of sulfating reagent, the molar ratio of sulfating reagent to CMS, reaction time, and temperature on the degree of substitution of sulfate groups (DS) of CMSS were studied. Meantime, the DS of each CMSS was determined by barium sulfate–glutin nephelometery method. Moreover, the anticoagulant activity of CMSS was investigated by the coagulation assays of activated partial thromboplastin time, thrombin time, and prothrombin time. The results revealed that the anticoagulant activity of CMSS was closely related to the DS value and concentration. The anticoagulant activity was promoted with the increasing of the DS and concentration. The molecular weight (M_w) in measured range had little impact on anticoagulant activity in contract to the DS and concentration. In this article, the CMSS with the DS of 1.91, concentration of 75 μg/mL and the M_w of 2.61 × 10⁴ had the best blood anticoagulant activities. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Formation of polyelectrolyte complexes between cellulose derivatives and their blood compatibility

Formation of polyelectrolyte complexes (PECs) between cellulose derivatives in aqueous solution and their blood compatibility were examined. To this end, two types of quaternary ammonium cellulose derivatives, Q-Cell and Q-HEC, were prepared by treating cellulose and hydroxyethyl cellulose (HEC), respectively, with glycidyl trimethylammonium chloride. Anionic derivatives were carboxymethyl cellulose (CMC) with different degrees of substitution (DS) and cellulose sulfate (CS). In vivo blood tests were made by a method of peripheral vein indwelling suture. The results showed that the complex formation of Q-Cell did not follow a stoichiometric reaction, but Q-HEC reacted stoichiometrically with CMC and CS. It was also found that water-insoluble cellulosic PECs are soluble in formic acid, showing that the cellulosic PEC films can be prepared from formic acid solutions. The blood tests revealed that by the criteria of the test method employed in this work, cellulosic PECs had a good blood compatibility.     

Esterification of cellulose with acyl-1H-benzotriazole

For the first time, the acylation of cellulose was realized by activation of carboxylic acid with 1H-benzotriazole. The reaction could be carried out under mild conditions. The acyl-1H-benzotriazole reacts with cellulose leading to cellulose acetate, butyrate, caproate, benzoate, myristate, and stearate with DS values between 1.07 and 1.89. The reaction proceeds completely homogeneously in dimethyl sulfoxide (DMSO)/TBAF × 3H₂O (tetrabutylammonium fluoride trihydrate) using acyl-1H-benzotriazole as acylation agent. The cellulose esters were characterized by means of ¹H NMR, GPC measurements, and solubility tests.     

Cellulose derivatives with adamantoyl groups

A new synthesis pattern of adamantoyl esters of cellulose (AdTMSC) is described. The process was approached by two steps. The first one consists in the obtaining of trimethylsilylcellulose (TMSC), by reacting cellulose in N,N‐dimethylacetamide/lithium chloride (DMA/LiCl) solution with chlorotrimethylsilane and hexamethyldisilazane. The AdTMSC was synthesized by reacting trimethylsilylcellulose with 1‐adamantanecarbonyl chloride, at 130°C. The obtained compounds were characterized by elemental analysis, ¹H and ¹³C NMR, FTIR spectroscopy, thermogravimetry method, and X‐ray diffraction. From ¹H NMR spectroscopy and elemental analyses, the degree of substitution (DS) of the cellulose derivatives was established. The AdTMSC is soluble in common organic solvent like chloroform, THF, and DMSO. As revealed by ¹³C NMR spectroscopy, a faster reaction takes place at the O (6)H group from AGU compared with O (2)H or O(3)H groups. Furthermore, other important properties were established by X‐ray diffraction and thermogravimetry method. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 105–112, 2006     

Influence of wood pulp quality on the structure of carboxymethyl cellulose

The quality of carboxymethyl cellulose (CMC) prepared from different wood-derived market pulps is examined. The pulps represent kraft and sulfite qualities with different levels of hemicellulose (1.5–22.8 wt %), intrinsic viscosity (391–780 mL g⁻¹), and content of extractives (0.04–0.13 wt %). The pulps are carboxymethylated in aqueous medium at three different levels of sodium hydroxide concentration, resulting in three levels of degree of substitution (DS), 0.3, 0.7–0.8, and 1.3–1.4 (according to nuclear magnetic resonance spectroscopy and high-performance liquid chromatography). CMC with DS 0.7–0.8 is found to be near the limit for water solubility and the resulting ranking for that solubility is shown to be correlated to DS. The DS is found to be impaired by a high content of impurities and high degree of Cellulose II in the pulp. The sulfite pulps yield CMC with the best solubility in water. A high level of extractives does not interfere with reactivity. Moreover, it is found that impurities, such as lignin and xylan, inhibit thickening behavior even at high DS, and that the ratio of substitution on Position 3 is a measure of the xylan content, which suggests that this position in xylan has extremely high reactivity. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47862.     

Experimental study on carboxymethylation of cellulose extracted from Posidonia oceanica

The production of carboxymethylcellulose (CMC) from bleached cellulose pulps obtained from Posidonia oceanica was explored. The optimal reaction conditions were studied for the carboxymethylation of cellulose in organic liquids. The carboxymethylation reaction was carried out with NaOH and monochloroacetic acid (MAC) as the reagent. Different alcohols were compared in terms of the degree of substitution (DS). The highest DS was obtained with n‐butanol. For this alcohol, the effects of the temperature, alkali concentration, and MAC concentration were studied. The reaction was also carried out in three consecutive steps. The resulting CMC had a DS of about 2.75. The functionalization of cellulose was checked using FTIR spectroscopy and ¹³C‐NMR. The X‐ray analysis showed that the crystalline structure of cellulose decreased when the DS increased and the structure was totally amorphous in high DS material. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 99: 1808–1816, 2006     

Influence of structure of cyclic urea derivatives on their reactivities with cotton

The structure of the cyclic urea influenced the rate of reaction with cotton cellulose and the mechanism by which reaction occurred. Reaction of N, N′-dimethylolethylene-urea (DMEU) and N, N′-dimethylolpropyleneurea (DMPU) with cellulose in presence of inorganic salt catalysts proceeded through methylol hydroxyls and at the same rate; but reaction mechanism differed. With DMEU, N → metal ion coordination occurred and S_N2 mechanism prevailed. With DMPU, O → metal ion coordination resulted. Reaction of dihydroxyethylene urea (DHEU), N, N′-dimethyldihydroxyethyleneurea (DMeDHEU), and N, N′-dimethyloldihydroxyethyleneurea (DMDHEU) with cotton cellulose proceeded through ring hydroxyls with the formation of a carbonium ion, indicating an S_N1 mechanism. The much faster rate of reaction with DMeDHEU than with DHEU was attributed to the more electronegative environment of its ring hydroxyl, while the much slower rate of reaction of DMDHEU was attributed to hydrogen bonding between its methylol and ring hydroxyls.     

Alkaline treatment of diacetate fibers and subsequent cellulase degradation

The work investigated the degradation behavior of cellulose acetate (CA) fibers in NaOH solutions in heterogeneous conditions and the effect of alkaline treatment on cellulase degradation of CA fibers. Weight analysis and IR spectra showed that the weight loss of CA fibers immersed in NaOH solution chiefly depended on acetylation. Alkaline treatment promoted the degradation of CA fibers in cellulase solution by reason of deacetylation, especially when the degree of substitution (DS) of CA fibers reached 0.8, cellulase degradation increased most markedly. SEM revealed a smooth surface except some thin holes in the CA fibers after immersion in NaOH solution with a lower concentration because of the formation of alkaline cellulose, and only in a higher concentration such as 5.0N, it could be observed that microfibers perpendicular to fiber axis distributed over the surfaces of the fibers. ¹NMR spectra suggested that only in a lower NaOH concentration (≤0.25N), deacetylation reaction was affected by the reactivities of ester groups at position 2, 3, and 6 in anhydroglucose unit, but did not follow the theoretical trend in the three positions. Moreover, the DS for polymer molecules in CA fibers were dispersive after alkaline treatment in heterogeneous condition and the DS of the product increased during sequent cellulase degradation. This was also demonstrated by the result of IR analysis and X‐ray diffraction. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

New methods for acylation of pure and sawdust‐extracted cellulose by fatty acid derivatives—Thermal and mechanical analyses of cellulose‐based plastic films

This work deals with the synthesis of cellulosic plastic films obtained in homogeneous conditions by microwave‐induced acylation of commercial or chestnut tree sawdust cellulose by fatty acids. The acylation reaction was studied according to N,N‐dimethyl‐4‐aminopyridine (DMAP) amount, DMAP simultaneously playing the role of catalyst and proton trapping base. This study clearly showed that DMAP does not influence degrees of substitution (DS), massic, and molar yields. Plastic films synthesized in the absence of DMAP showed a decrease in mechanical behavior. Organic (tributylamine) or inorganic bases (CaCO₃, Na₂CO₃) were then added to replace DMAP basic activity, and no changes were observed. Concerning thermal and mechanical properties of plastics obtained with various bases, glass transition temperatures (T_g) and degradation temperature (T_d) were found constant whatever the base, and the best mechanical properties were obtained for films synthesized in the presence of CaCO₃. The same remarks were made concerning the valorization of chestnut tree sawdust cellulose. Microbial biodegradation of plastic films with DS = 2.2 led to a loss of their mechanical behaviors. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 97: 1266–1278, 2005