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Cellulose Derivatives (cellulose + derivative)
Selected AbstractsElectrospinning of cellulose-based nanofibersJOURNAL OF APPLIED POLYMER SCIENCE, Issue 3 2007Audrey Frenot Abstract Cellulose derivatives of carboxymethyl cellulose sodium salt (CMC), hydroxypropyl methylcellulose (HPMC), methylcellulose (MC), and enzymatically treated cellulose have been electrospun, and the microstructure of the resulting nanofibers has been analyzed by scanning electron microscopy (SEM). Before electrospinning, the solutions were characterized by viscometry and surface tension measurements, and the results were correlated with spinnability. Four different CMC derivatives, varying in molecular weight (Mw), degree of substitution (DS), and substitution pattern, have been electrospun in mixtures with poly(ethylene oxide) (PEO), and nanofibers of various characteristics have formed. The CMC-based nanostructures, i.e., the nonwoven sheet and individual nanofibers, proved to be independent of Mw and DS but largely dependent on the substitution pattern. The nonwoven sheets varied in homogeneity, and beads appeared on the individual fibers. Depending on the chemical nature of the CMC, the extraction of PEO resulted in pure CMC nanostructures of varying appearance, indicating that the distribution of PEO and CMC in the nanofibers also varied. Two different HPMC derivatives, varying in DS, were electrospun into nanofibers. Homogeneous nonwoven sheets based on nanofibers of similar appearance are formed, independent of the substitution content of the HPMC sample. Preliminary fibers were obtained from enzymatically treated cellulose in a solvent system based on lithium chloride dissolved in dimethyl acetamide (LiCl: DMAc). © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 1473,1482, 2007 [source] Nature of water molecules in hydrogels based on a liquid crystalline cellulose derivativePOLYMERS FOR ADVANCED TECHNOLOGIES, Issue 11-12 2003P. Wojciechowski Abstract The status and nature of water molecules in hydrogels with a liquid crystalline organization of the polymer network based on a biopolymer were investigated. Liquid crystalline (LC) hydrogels were obtained in situ by the photopolymerization of acrylic acid into the lyotropic liquid crystalline phase of (2-hydroxypropyl)cellulose in a solvent mixture of water and acrylic acid. The photopolymerization of acrylic acid in the lyotropic liquid crystalline phase at room temperature gives a hydrogel in which liquid crystalline order and water are retained. The liquid crystalline hydrogel contains water, which originates from the composition of the lyotropic liquid crystalline phase, and may also contain water after immersion in liquid water. The water molecule characteristics were examined by means of differential scanning calorimetry, dielectric relaxation spectroscopy, and differential scanning calorimetry coupled with thermo-optical measurements. The swelling data were obtained by using a weighing method. The investigations reveal the different nature of the two above-mentioned water types. For the water from the composition of the lyotropic liquid crystalline phase, the phase transitions,typical for the bulk water,were not observed, in contract to the water after swelling of the liquid crystalline hydrogel in the liquid water. The results of the measurements suggest that water, which comes from the composition of the lyotropic liquid crystalline phase, forms,together with a polymer network,a microstructure, stabilized by this water. The water, after swelling of the LC hydrogel in the liquid water, is separated in the pores of the hydrogel and exhibits the phase transitions of the bulk water. Copyright © 2003 John Wiley & Sons, Ltd. [source] Cellulose as a renewable resource for the synthesis of wood consolidantsJOURNAL OF APPLIED POLYMER SCIENCE, Issue 5 2010Giacomo Cipriani Abstract Crosslinkable cellulose ethers as allyl cellulose, allyl carboxymethyl cellulose, and allyl n -hydroxypropyl cellulose were synthesized and characterized, and their use as consolidating agents for waterlogged wood was studied. For this kind of application, structural properties similar to those of wood's polysaccharide components are desired in the design stage of new consolidants. The choice to synthesize cellulose ethers was determined from the possibility of using cellulose as the starting material because of its large availability in nature, biocompatibility, and low cost. In addition, cellulose ethers are quite easy to obtain, and they can have different properties, depending on the nature and the amount of the functional groups introduced. For this purpose, a cellulose with a lower degree of polymerization was also used for the synthesis of related cellulose ethers. By means of Fourier transform infrared spectroscopy, the affinity of the cellulose derivatives for degraded lignin flours was detected. The preliminary results of this study show that these polysaccharide compounds may be proposed as wood consolidating agents. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010 [source] Structure and mechanical properties of cellulose derivatives/soy protein isolate blendsJOURNAL OF APPLIED POLYMER SCIENCE, Issue 5 2008Ziyan Zhou Abstract Biodegradable and biocompatible composites based on soy protein isolate (SPI) and various cellulose derivatives have been prepared, and the dependence of structures and mechanical properties on the content and species of cellulose derivatives for the composites were investigated by X-ray diffraction, differential scanning calorimetry, scanning electron microscope, and tensile test. The selected cellulose derivatives, such as methyl cellulose (MC), hydroxyethyl cellulose (HEC), and hydroxypropyl cellulose, were miscible with SPI when the content of cellulose derivatives was low, and then the isolated crystalline domains, shown as the structures of network and great aggregate, formed with an increase of cellulose derivative content. The miscible blends could produce the higher strength, and even result in the simultaneous enhancement of strength and elongation for the HEC/SPI and MC/SPI blends. Meanwhile, the moderate content of great MC domains also reinforced the materials. However, the damage of original ordered structure in SPI gave the decreased modulus. Since all the components, i.e., cellulose derivatives and soy protein, are biocompatible, the resultant composites are not only used as environment-friendly material, but the biomedical application can be expected, especially for the tissue engineering scaffold. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008 [source] Preparation and optimization of 2,4-D loaded cellulose derivatives microspheres by solvent evaporation techniqueJOURNAL OF APPLIED POLYMER SCIENCE, Issue 4 2007Z. El Bahri Abstract Controlled release herbicide formulations were prepared by microencapsulation using solvent evaporation technique. 2,4-D was chosen as core material, which was microencapsulated in two cellulose derivatives as matrices: cellulose acetate butyrate butyryl (CAB) and ethylcellulose (EC). The work is intended to produce systems containing the herbicide to reduce its risks by dermal contact, evaporation, or degradation and to control the release of the active agent. The microspheres loaded by 2,4-D were characterized by scanning electron microscopy and infrared spectroscopy. We have obtained microparticles in the range of D32 of 42,277 ,m with CAB and 88,744 ,m with EC by varying the process parameters. The drug entrapment was improved by controlling certain factors such as polymer/solvent ratio, pH of continuous phase, and organic phase solvent. The drug release was established in deionized water at pH = 5.5 and 25°C and the 2,4-D concentrations were estimated by UV analysis. The release data were analyzed according to Fick's law and the results demonstrate that the release rate can be controlled by modifying the process parameters. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 2742,2751, 2007 [source] Thermogravimetric investigation of the hydration behaviour of hydrophilic matricesJOURNAL OF PHARMACEUTICAL SCIENCES, Issue 4 2010Lorena Segale Abstract This article proposes thermogravimetric analysis (TGA) as a useful method to investigate the hydration behaviour of hydrophilic matrix tablets containing hydroxypropylmethylcellulose (HPMC), sodium carboxymethylcellulose (NaCMC) or a mixture of these two polymers and four drugs with different solubility. The hydration behaviour of matrix systems was studied as a function of the formulation composition and of the dissolution medium pH. TGA results suggest that the hydration of matrices containing HPMC is pH-independent and not affected by the characteristics of the loaded drug; this confirms HPMC as a good polymer to formulate controlled drug delivery systems. On the other hand, the performances of NaCMC matrix tablets are significantly affected by the medium pH and the hydration and swelling of this ionic polymer is influenced by the loaded drug. For systems containing the two polymers, HPMC plays a dominant role in the hydration/dissolution process at acidic pH, while at near neutral pH both the cellulose derivatives exert a significant influence on the hydration performance of systems. The results of this work show that TGA is able to give quantitative highlights on the hydration behaviour of polymeric materials; thus this technique could be a helpful tool to support conventional hydration/swelling/dissolution studies. © 2009 Wiley-Liss, Inc. and the American Pharmacists Association J Pharm Sci 99: 2070,2079, 2010 [source] Olefin metathesis applied to cellulose derivatives,Synthesis, analysis, and properties of new crosslinked cellulose plastic filmsJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 2 2005Nicolas Joly Abstract New crosslinked cellulose-based plastic films were synthesized with olefin metathesis as a crosslinking reaction. Microcrystalline cellulose was first dissolved in a lithium chloride/N,N -dimethylacetamide solvent system and acylated by ,-undecenoyl chloride under microwave irradiation with N,N -dimethyl-4-aminopyridine as the catalyst. Cellulose unsaturated fatty acyl esters with a degree of substitution (DS) ranging from 1.4 to 2.0 were then crosslinked by olefin metathesis with a first generation Grubbs catalyst. Crosslinking ratios (T) ranging from 20 to 90% were obtained for low catalyst amounts (<1.2%), but gels appeared when T was too high. To avoid this gel formation, cellulose was acylated with a mixture of lauroyl and ,-undecenoyl chlorides. This internal dilution allowed us to obtain films of every case and various T (varying from 10 to 80% for a catalyst amount below 3.5%). Plastics were characterized by Fourier transform infrared (FTIR) spectroscopy, and the fatty acid mixture resulting from the hydrolysis of cellulose esters were analyzed by gas chromatography (GC) and NMR spectroscopy. Mechanical properties showed that the elastic modulus and tensile failure stress was higher when the plastic films were crosslinked. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 407,418, 2005 [source] Novel Biopolymer Structures Synthesized by Dendronization of 6-Deoxy-6-aminopropargyl celluloseMACROMOLECULAR RAPID COMMUNICATIONS, Issue 21 2008Matthias Pohl Abstract Propargyl cellulose with regioselective functionalization pattern was synthesized by nucleophilic displacement reaction of 6- O -toluenesulfonyl ester of cellulose (degree of substitution, DS 0.58) with propargyl amine. The novel 6-deoxy-6-aminopropargyl cellulose provides an excellent starting material for the selective dendronization of cellulose at position 6 via the copper-catalyzed Huisgen reaction yielding 6-deoxy-6-amino-(4-methyl-[1,2,3-triazolo]-1-propyl-polyamido amine) cellulose derivatives of first- (DS 0.33) and second (DS 0.25) generation, which are soluble in polar aprotic solvents. The novel biopolymer derivatives were characterized by elemental analysis, FT-IR spectroscopy, and one- and two dimensional NMR spectroscopy, showing no side reactions (cross-linking) or impurities and no conversion at the secondary positions. [source] Regioselective Dendritic Functionalization of CelluloseMACROMOLECULAR RAPID COMMUNICATIONS, Issue 24 2004Mohammad L. Hassan Abstract Summary: A series of regioselectively dendronized cellulose derivatives has been prepared by the treatment of cellulose in a N,N -dimethylacetamide/LiCl solvent system with dendrons possessing isocyanate focal substituents. These new materials were characterized using FT-IR and 13C NMR spectroscopies, and thermogravimetric analysis; the products were highly soluble in a wide range of organic solvents. Substitution pattern of the dendronized cellulose. [source] New ways to enhance the functionality of paperboard by surface treatment,,,a reviewPACKAGING TECHNOLOGY AND SCIENCE, Issue 6 2008Caisa Andersson Abstract This review summarizes recent development of functional materials to improve the barrier properties of paperboard with emphasis on bio-based polymers. Focus is directed to novel application techniques and water-borne, renewable coating materials. Some aspects on substrate properties and the requirements on food packaging are discussed as are the processability, convertability, recyclability and biodegradability of packaging materials. The functionality, advantages and disadvantages of several bio-based polymers are presented in detail. Among these are starch and cellulose derivatives, chitosan, alginate, wheat gluten, whey proteins, polycaprolactone, poly(lactic acid) and polyhydroxyalkanoates. Also discussed is the enhancement of barrier properties by incorporation of nanosized materials, by application of thin protective top coatings and local reinforcement by self-healing agents. Copyright © 2008 John Wiley & Sons, Ltd. [source] Determination of molar mass and solution properties of cationic hydroxyethyl cellulose derivatives by multi-angle laser light scattering with simultaneous refractive index detectionPOLYMER INTERNATIONAL, Issue 10 2009Wei Gao Abstract BACKGROUND: A complete understanding of the molar mass and solution properties of raw materials in bio/pharmaceutical products under bio-application and natural conditions ensures process control, product performance and quality. Biopolymers including polymeric cationic hydroxyethyl cellulose derivatives (e.g. Polyquaterium-10 or Polymer JR) have long been used in health care formulations including shampoos, lotions, eye drops and contact lens multi-purpose solutions. Previously reported molar masses and conformation of Polymer JR were based on size exclusion chromatography-related techniques, which required highly concentrated buffered salt solutions and organic solvent modifiers to prevent undesirable interactions, and did not represent the isotonic conditions in products and applications. RESULTS: This paper describes the characterization of Polymer JR in saline using a new approach that combines micro-batch mode multi-angle laser light scattering with simultaneous refractive index measurements (MB-MALLS-RI). Mass-average molar mass, z -average radius of gyration and second virial coefficient values in phosphate buffer saline (PBS) were obtained and are discussed in detail. CONCLUSION: The molar mass and solution properties of Polymer JR in PBS, with the same pH and ionic strength as most health care solution products, can be characterized using the MB-MALLS-RI technique. The approach is practical and can be widely used for the analysis of other cationic biopolymers. Copyright © 2009 Society of Chemical Industry [source] Synthesis and NMR characterization of 6-Phenyl-6-deoxy-2,3-di- O -methylcellulose,POLYMERS FOR ADVANCED TECHNOLOGIES, Issue 6 2002Dr Navzer (Nozar) D. Sachinvala Abstract Cellulose (1) was converted for the first time to 6-phenyl-6-deoxy-2,3-di- O -methylcellulose (6) in 33% overall yield. Intermediates in the five-step conversion of 1 to6 were: 6- O -tritylcellulose (2), 6- O -trityl-2,3-di- O -methylcellulose (3), 2,3-di- O -methylcellulose (4); and 6-bromo-6-deoxy-2,3-di- O -methylcellulose (5). Elemental and quantitative carbon-13 analyses were concurrently used to verify and confirm the degrees of substitution in each new polymer. Gel permeation chromotography (GPC) data were generated to monitor the changes in molecular weight (DPw) as the synthesis progressed, and the compound average decrease in cellulose DPw was , 27%. Differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA) were used to characterize the decomposition of all polymers. The degradation temperatures (,°C) and percent char at 500,°C of cellulose derivatives 2 to 6 were 308.6 and 6.3%, 227.6,°C and 9.7%, 273.9,°C and 30.2%, 200.4,°C and 25.6%, and 207.2,°C and 27.0%, respectively. The glass transition temperature (Tg) of6- O -tritylcellulose by dynamic mechanical analysis (DMA) occurred at 126.7,°C and the modulus (E,, Pa) dropped 8.9 fold in the transition from ,150,°C to,+,180,°C (6.6,×,109 to 7.4,×,108 Pa). Modulus at 20,°C was 3.26,×,109 Pa. Complete proton and carbon-13 chemical shift assignments of the repeating unit of the title polymer were made by a combination of the HMQC and COSY NMR methods. Ultimate non-destructive proof of carbon,carbon bond formation at C6 of the anhydroglucose moiety was established by generating correlations between resonances of CH26 (anhydroglucose) and C1,, H2,, and H6, of the attached aryl ring using the heteronuclear multiple-bond correlation (HMBC) method. In this study, we achieved three major objectives: (a) new methodologies for the chemical modification of cellulose were developed; (b) new cellulose derivatives were designed, prepared and characterized; (c) unequivocal structural proof for carbon,carbon bond formation with cellulose was derived non-destructively by use of one- and two-dimensional NMR methods. Copyright © 2002 John Wiley & Sons, Ltd. [source] Chain stiffness of heteropolysaccharide from Aeromonas gum in dilute solution by dynamic light scatteringBIOPOLYMERS, Issue 6 2002Xiaojuan Xu Abstract Dynamic light scattering measurements have been made on 15 fractions of aeromonas (A) gum, an extracellular heteropolysaccharide produced by the strain Aeromonas nichidenii, with dimethylsulfoxide containing 0.2M lithium chloride as the solvent at 25°C. Data for the translational diffusion coefficient D covering a molecular weight range from 4.5 × 105 to 2.1 × 106 and ratios of the z -average radius of gyration ,s2,z1/2 to the hydrodynamic radius RH (calculated with previous ,s2,z data) suggest that the polymer behaves like a semiflexible chain in this solvent similar to the stiffness of cellulose derivatives. Thus the D data are analyzed on the basis of the Yamakawa,Fujii theory for the translational friction coefficient of a wormlike cylinder by coarse-graining the heteropolysaccharide molecule. Excluded-volume effects are taken into account in the quasi-two-parameter scheme, as was done previously for ,s2,z and [,] (the intrinsic viscosity) of A gum in the same solvent. The molecular weight dependence of RH is found to be explained by the perturbed wormlike chain with a persistence length of 10 nm, a linear mass density of 1350 nm,1, an excluded-volume strength parameter of 1.3 nm, and a chain diameter of 2.8 nm. These parameters are in substantial agreement with those estimated previously from ,s2,z and [,] data, demonstrating that the solution properties (D, ,s2,z, and [,]) of the heteropolysaccharide are almost quantitatively described by the current theories for wormlike chains in the molecular weight range studied. © 2002 Wiley Periodicals, Inc. Biopolymers 65: 387,394, 2002 [source] |