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1.
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.  相似文献   

2.
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  相似文献   

3.
A series of pH‐sensitive composite hydrogel beads, carboxymethyl cellulose‐g‐poly(acrylic acid)/attapulgite/sodium alginate (CMC‐g‐PAA/APT/SA), were prepared by combining CMC‐g‐PAA/APT composite and SA, using Ca2+ as the ionic crosslinking agent and diclofenac sodium (DS) as the model drug. The effects of APT content and external pH on the swelling properties and release behaviors of DS from the composite hydrogel beads were investigated. The results showed that the composite hydrogel beads exhibited good pH‐sensitivity. Introducing 20% APT into CMC‐g‐PAA hydrogel could change the surface structure of the composite hydrogel beads, decrease the swelling ability, and relieve the burst release effect of DS. The drug cumulative release ratio of DS from the hydrogel beads in simulated gastric fluid was only 3.71% within 3 hour, but in simulated intestinal fluid about 50% for 3 hour, 85% for 12 hour, up to 90% after 24 hour. The obtained results indicated that the CMC‐g‐PAA/APT/SA hydrogel beads could be applied to the drug delivery system as drug carriers in the intestinal tract. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011  相似文献   

4.
Carboxymethylcellulose (CMC) is a cellulose derivative obtained by the carboxymethylation of some hydroxyl groups in the cellulose macromolecules. In this article, we use CMC as a model compound of cellulose fibers to study polyamineamide epichlorohydrin (PAE)–fibers interactions during the preparation of PAE‐based wet strength papers. The main advantages of the use of CMC to replace cellulose fibers are its water‐soluble character and the homogeneous reaction medium during mixing with PAE resin. Based on 13C cross‐polarization/magic angle spinning nuclear magnetic resonance (CP/MAS NMR) and Fourier transformed infra‐red (FTIR) spectroscopy, we prove the formation of ester bonds in PAE–CMC films boosted by a thermal posttreatment at 105°C for 24 h. These ester bonds are derived from a thermally induced reaction between carboxyl groups in the CMC structure and azetidinium ions (AZR) in the PAE resin. PAE‐based handsheets were prepared from 100% Eucalyptus fibers. After preparation, some samples were thermally posttreated (TP) at 130°C for 10 min and stored under controlled conditions (25°C and 50% relative humidity or RH). For lowest PAE dosage, storage of the not thermally posttreated (NTP) PAE‐based handsheets does not allow them to reach the tensile strength values of TP PAE‐based handsheets (at 130°C for 10 min), but the difference in terms of breaking length remains low. For the highest PAE addition level, NTP and TP PAE‐based handsheets exhibit close values of the breaking length from 30 days of storage under controlled conditions (25°C and 50% RH). When a thermal posttreatment is applied, the wet strength development of PAE‐based papers is a combined effect of homo‐ and co‐cross‐linking mechanisms. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42144.  相似文献   

5.
A study of the carboxymethylation of wood pulp cellulose and cotton linters cellulose in different organic media, namely, ethanol, acetone, and ethanol-acetone mixtures, is performed. Previously, the ethanol-acetone 1 : 1 (w/w) mixture used as reaction medium was found to give a higher degree of substitution (DS) than the pure solvents separately. In the present work, the kinetic investigation of cellulose carboxymethylation was carried out in ethanol-acetone 3 : 7 (w/w) mixture, as well as in acetone as reaction media, and the same synergistic effect of the solvents mixture was observed. The data suggested a pseudo-first-order kinetic behavior satisfactorily described by the following equation: ln(1.11 − DS) = −kt. The two reaction steps observed are related to the transformations of less ordered regions with higher reaction rate and more ordered regions with smaller reaction rates, respectively. A possible explanation for this behaviour is given, taking into account the different structural changes of cellulose crystallinity and accessibility produced by ethanol-acetone 3 : 7 (w/w) mixture, ethanol, and acetone, as revealed by X-ray diffraction and calorimetry determinations. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 67: 481–486, 1998  相似文献   

6.
Carboxymethylcellulose (CMC) was prepared in a completely heterogeneous procedure in an isopropanol/water slurry and the influence of the reaction conditions on the pattern of functionalization within the anhydroglucose repeating unit as well as due to the formation of the four main repeating units (i. e. unfunctionalized, mono-, di-, and tricarboxymethylated) was checked. The concentration of aqueous sodium hydroxide solution, which is used to activate the cellulose, was varied in the range from 8 to 30% at reaction times from 2 to 6 h at 55°C. The reaction with sodium monochloroacetate leads to the highest degree of substitution (DSCMC) of 1.24 at a NaOH concentration of 15% and 5 h reaction time. Using a lye concentration of 30%, no influence of the reaction time between 2 h and 6 h was found. From 1H NMR spectroscopical studies it was concluded that both the concentration of the alkali hydroxide solution and the reaction time influence the partial DSCMC at positions O-2 and O-6, while position O-3 shows the lowest reactivity in any case, independent of the reaction conditions used. With increasing lye concentration, carboxymethylation occurs preferably at O-6. Information about the content of the differently functionalized repeating units can be obtained by chromatographic analysis after complete depolymerization of the polymer chains. Surprisingly, in any product synthesized a statistic content of the building units of the polymer was found even at low activation of cellulose.  相似文献   

7.
Cyclodextrin‐grafted cellulosic hydrogel beads (CD+@HEC‐CMC‐gel) were prepared through electrostatic and host–guest interactions. β‐Cyclodextrin (CD+) modified with quaternary ammonium groups was used as the electropositive binding site, and carboxymethyl cellulose (CMC) in a double‐network hydrogel structure was used as the electronegative binding site. The double‐network structure was obtained by controlling the crosslinking of CMC and hydroxyethyl cellulose (HEC) in the presence of epichlorohydrin. The electrostatic interaction was used to graft CD+ onto the electronegative double‐network structure. Scanning electron microscopy indicated an obvious change in the cellulosic double network after grafting of CD+. The grafting content of CD+ in CD@HEC‐CMC‐gel is determined as 93.10 ± 0.74% by the photometric titration method. In order to evaluate the assembling and releasing ability, ibuprofen (IBU) was selected to be encapsulated in CD+@HEC‐CMC‐gel by host–guest interaction. In addition, the release of IBU by the hydrogel beads was explained by several kinetic models. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 46593.  相似文献   

8.
In this work, cationic cellulose (CC) with different degrees of substitution (DS) was successfully synthesized by the reaction between cellulose and 3‐chloro‐2‐hydroxypropyl‐trimethylammonium chloride (CHPTAC) in a 7 wt % NaOH and 12 wt % urea aqueous solution. The structure of the CC was characterized by using elemental analysis, 1H‐NMR, and FTIR. The DS values of CC ranged between 0.18 and 0.50, which could be obtained by adjusting the reaction temperature, reaction time, and molar ratio of CHPTAC to anhydroglucose unit of cellulose. The cationic cellulose–graft–polyacrylamide flocculant (CC‐g‐PAM) based on CC and polyacrylamide (PAM) was also synthesized in a homogeneous aqueous solution. The flocculation characteristics of CC and CC‐g‐PAM were evaluated in a kaolin suspension. The results showed that CC‐g‐PAM was an effective flocculant for the kaolin suspension under acidic or neutral conditions, and the flocculation efficiency was over 90%, while the CC showed better flocculation performance under alkaline conditions. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43106.  相似文献   

9.
Sulfonic acid esters of differently linked polysaccharides including cellulose, dextran, lichenan, and pullulan were synthesized homogeneously applying N,N‐dimethylacetamide/LiCl as the solvent. The dependence of the degree of substitution (DS) on the molar ratio of repeating unit to sulfonic acid chloride and on the structure of the reagent (benzene‐, p‐toluene‐, 4‐chlorobenzene‐, 2,4‐dinitrobenzene‐, 2,4,6‐trimethylbenzene‐, and 2,4,6‐triisopropylbenzene sulfonic acid chloride), as well as on the polysaccharide, was studied. DS values in the range of 0.2–2.3 were obtained. Bulky and electron withdrawing substituents on the aromatic ring inhibited ester formation. None of the sulfonic acid chlorides applied showed distinct regioselectivity. The polysaccharide sulfonic acid esters were soluble in organic solvents depending on the type of substituent and the degree of substitution. The molecular structure of the new polymers was confirmed by elemental analysis, FTIR, and 13C‐NMR spectroscopy. Subsequently, nucleophilic displacement reactions were carried out, which showed that the reactivity of the primary sulfonic acid ester group was higher than that of the secondary ones. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 2142–2150, 2006  相似文献   

10.
A series of novel polymeric cationic surfactants based on low molecular weight chitosan (LWCS) and 3‐chloro‐2‐hydroxypropyl dimethyl dehydroabietyl ammonium chloride (CHPDMDHA), LWCS‐g‐CHPDMDHA, were obtained by the grafting modification of LWCS with CHPDMDHA as grafting agent. The structure of LWCS‐g‐CHPDMDHA was confirmed by FT‐IR and 1H NMR, and the degree of quaternizing substitution (DS) of LWCS‐g‐CHPDMDHA was determined according to the results of elemental analysis. The aggregation behavior and surface activities of LWCS‐g‐CHPDMDHA in aqueous solution were investigated by transmission electron microscopy (TEM) and determination of surface tension, respectively. The experimental results showed that the DS and molecular weight (Mw) of LWCS have significant influence on the critical micelle concentrations (CMC) and the surface tensions at the CMC (γcmc). The shape of aggregates changed with the variation of concentration of LWCS‐g‐CHPDMDHA in aqueous solution. When the LWCS‐g‐CHPDMDHA was utilized as an emulsifier, the increase of DS of LWCS‐g‐CHPDMDHA and Mw of LWCS were favorable for improving the stability of emulsions composed of water and benzene.  相似文献   

11.
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  相似文献   

12.
Cassia obovata gum was isolated from cassia obovata seeds, the yield of the gum was 22.5% of the original seed weight. The gum was subjected to chemical modification via carboxymethylation under a variety of conditions. Variables studied include concentration of the etherifying agents and the preparation medium. The modification increases the solubility of the gum in cold water, and increases the stability of its pastes to microorganisms. Pastes of these derivatives are characterized by non‐Newtonian pseudoplastic behavior regardless of their degree of substitution (DS) and/or preparation medium, while their apparent viscosity decreases by increasing the DS. The effect of storing of these pastes on the rheological properties was also studied. The overall fastness properties for the fabrics printed using carboxy methyl cassia obovata gum either alone or in admixture with sodium alginate and/or CMC before and after storing are nearly identical to those printed using the conventional thickeners.  相似文献   

13.
Skin loss can be caused by accident, burn, trauma, chronic wounds, and diseases, which is severely aggravated by multidrug‐resistant bacterial infections. Soft hybrids based on biopolymers combined with silver nanoparticles (AgNPs) have potential applications as wound dressing supports and skin tissue repair. Thus, our study focused on the design, green synthesis, and comprehensive characterization of carboxymethyl cellulose (CMC–AgNP) nanocomposites for producing hydrogel membranes, with tunable physicochemical properties, cytocompatibility, and biocidal activity for potential application as wound dressing and skin repair. These nanocomposites were prepared using CMC with two degrees of carboxymethylation, distinct concentrations of citric acid (CA) crosslinker, and AgNPs by in situ chemical reduction, forming hybrid membranes by the solvent casting method. The results demonstrated that superabsorbent hydrogels were produced with swelling and degradation behaviors dependent on the concentration of CA crosslinker, degree of carboxymethylation of CMC, and content of AgNP in the matrices. Moreover, the Fourier transform infrared spectroscopy analysis evidenced that the CMC functional groups (e.g., ? COOH and ? OH) were directly involved in the chemical reactions for the formation of AgNPs and hydrogel crosslinking pathway. These nanocomposites were cytocompatible using in vitro 3‐(4,5‐dimethyl‐2‐thiazolyl)‐2,5‐diphenyltetrazolium bromide cell viability assay with of human embryonic kidney cells. Conclusively, the CMC–AgNP nanohybrids demonstrated to be simultaneously non‐toxic combined with highly effective antibacterial activity against gram‐positive multi‐resistant wound/skin pathogens (Staphylococcus aureus) and moderate effect towards gram‐negative strains (Escherichia coli and Pseudomonas aeruginosa). © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 45812.  相似文献   

14.
Hydroxyethyl cellulose Acetate (HECA) was prepared starting from hydroxyethyl cellulose (HEC), acetic anhydride and perchloric acid which was used as catalyst. The synthesized product was characterized by FTIR, 13C NMR, and 1H NMR. Substitution degree (DS) of HECA was determined using FTIR spectra taking a classical titration method as reference. The 1H NMR spectroscopy was also used to confirm the results obtained by FTIR. The DS is substantially affected by the temperature, the time of reaction and especially the equivalent number (eq. nb.) of the acetic anhydride added. We have studied and discussed in the context of usage in modification reactions, the solubility of the HECA samples by varying their DS. This investigation was based on the determination of the Flory‐Huggins interaction parameters (χSP) using the partial Hansen solubility parameters (HSP). HSP of HEC and the HECA samples were calculated from the Van‐Krevlen‐Hoftyze (VKH) method and the T. Lindvig approximation. We have focused our work on predicting and controlling family solvents of HECA with various DS, to facilitate and to optimize the homogenous modification reaction conditions. From results on a range of HECA samples, it is conclude that their prediction solubility taking the value of DS into account is possible, and then the surface modification can relatively be easily realized. The thermal analysis study shows some differences in Tg and thermal degradation between HEC and HECA, moreover these thermal temperatures are influenced by DS values. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011  相似文献   

15.
A systematic spectrophotometric study on the complexation of chromium (III) ion with sodium carboxymethyl cellulose (CMC) was carried out. The effects of the degree of substitution (DS) of the polymer, the concentrations of Cr(III) and CMC solutions, the pH and temperature on the complex formation were studied in the aqueous state. CMC complexes with Cr(III) were characterized by elemental analysis, magnetic moment and spectral (Vis and IR) data. The results showed that CMC (L) chelated to the metal ion according to the formula CrL2 · 2H2O. The ligand field parameters, namely Dq, B and β were calculated; the β-values indicate strong covalency in the ligand σ bond. The IR spectra revealed that the chelating sites of CMC are not only the carboxymethyl groups, via the ether- and the carboxyl-oxygen atoms, but also the secondary hydroxyl groups.  相似文献   

16.
Carboxymethyl chitins and chitosans (CM‐chitins, CM‐chitosans) of different substitution sites were prepared under different reaction conditions, and partially depolymerized carboxymethyl chitins of various molecular weights from 24.8 × 104 to 0.26 × 104 were obtained by degrading with chemical reagents. Degree of substitution (DS) was estimated by potentiometric titration. Substitution site was confirmed by infrared and 13C‐NMR spectra. Molecular weights were determined with gel permeation chromatography and gel permeation chromatography combined with laser light scattering (GPC‐LLS). Moisture‐absorption and retention abilities of these compounds were tested in comparison with those of hyaluronic acid (HA). The results reveal that 6‐carboxymethyl group in the molecular structure of chitin and chitosan is a main active site responsible for moisture retention. Although carboxymethylation at OH‐3 and N position is not essential, they contribute to the ability. Moisture‐retention ability is also related to molecular weight; that is, higher molecular weight helps to improve moisture‐retention ability. 6‐O‐CM‐chitin (chitosan) with a DS above 0.8 and molecular weight higher than 24.8 × 104 has the potential to substitute for HA for use in cosmetics and clinical medicine. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 83: 1233–1241, 2002  相似文献   

17.
Several ethoxylated sugar fatty ester surfactants were prepared by the reaction of glucose with three fatty acids, namely, adipic, stearic and palmitic acids to produce GA, GS and GP esters. These glucose esters were then ethoxylated by four different molecular weight polyethylene glycols, namely, 400, 1,000, 2,000 and 4,000 mol L?1. The prepared ethoxylated esters (12 compounds) were characterized by IR and 1H‐NMR spectroscopy. The surface activity of the prepared compounds was thoroughly studied by measuring the surface tension of different solutions of these compounds at three temperatures, namely 298, 308 and 318 K. From the surface tension‐concentration plots of these compounds some surface properties, such as CMC (critical micelle concentration), Γmax (maximum surface excess concentration) and Amin (area occupied per molecule) were calculated. The surface properties of the prepared surfactants were correlated to their chemical structure. It was found that the CMC decreases when increasing the molecular weight of polyethylene glycols, whereas Amin increases. Furthermore, the demulsification test was carried out and the results of demulsification efficiency were correlated to the chemical composition of the investigated compounds. Some factors that affect the demulsification efficiency were also considered. The oil phase recovered from the treated sludge was characterized and mixed with fresh crude to improve its API.  相似文献   

18.
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.  相似文献   

19.
The aim of the present study is to investigate the influence of free, carboxymethyl cellulose (CMC) immobilised, PVA–alginate immobilised, and HCl treated rice husk on the removal of Direct Red‐31 and Direct Orange‐26 dyes. The biosorption capacity of the rice husk increased with HCl treatment (67.39 and 45.34 mg/g) and decreased with PVA–alginate immobilisation (9.73 and 10.03 mg/g) as compared to the free biomass (65.56 and 45.58 mg/g) at 200 mg/L dye concentration for Direct Red‐31 and Direct Orange‐26, respectively. Equilibrium data were best described by Langmuir Type 1 for Direct Red‐31 and Direct Orange‐26 (free, CMC immobilised, PVA–alginate immobilised, and HCl treated). Best correlation coefficients for Direct Red‐31 and Direct Orange‐26 using free, CMC immobilised, PVA–alginate immobilised, and HCl treated rice husk were obtained for pseudo‐second order and Elovich kinetic models. Values of Gibbs free energy (ΔG°) and enthalpy change (ΔH°) indicated that reaction was spontaneous and endothermic in nature at the studied temperatures. FT‐IR studies showed the involvement of carbonyl, carboxyl, and amide groups in the biosorption process. SEM exhibited the morphological changes on the biosorbent surface and BET analysis to determine the surface area is also carried out.  相似文献   

20.
Regenerated cellulose was prepared from microcrystalline cellulose (MCC) via dissolution in three well‐known nonderivatizing systems: ferric chloride/sodium tartarate/sodium hydroxide (FeTNa), sodium hydroxide/thiourea (NaOH/thiourea), and N‐methylmorpholine‐N‐oxide (NMMO) systems. The effect of regeneration using the different systems on the supramolecular structure of the regenerated celluloses was studied using X‐ray diffraction and Fourier transform infrared (FTIR). The effect of regeneration on supermolecular structure, morphology, and thermal stability of regenerated celluloses were studied using scanning electron microscopy (SEM) and thermogravimetric analysis (TGA). The effect of regeneration systems used on the chemical reactivity of cellulose toward carboxymethylation, acetylation, and cyanoethylation reactions was briefly studied. The results showed dependence of all the aforementioned properties on the dissolution reagent used in spite of that all studied reagents cause the same change in cellulose crystalline structure (from cellulose I to cellulose II). The degree of polymerization, crystallinity, and thermal stability of the regenerated cellulose (RC) samples were in the following order: NaOH/thiourea RC > FeTNa RC > NMMO RC. SEM micrograph showed unique surface for the NMMO RC sample. The reactivity of the different regenerated cellulose samples toward carboxymethylation, cyanoethylation, and acetylation depended mainly on the reaction system and conditions used rather than on crystallinity of regenerated cellulose. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008  相似文献   

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