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Crystalline Structure (crystalline + structure)
Selected AbstractsMorphology and Crystalline Structure of Poly(, -Caprolactone) Nanofiber via Porous Aluminium Oxide TemplateMACROMOLECULAR MATERIALS & ENGINEERING, Issue 9 2006Yang Chen Abstract Summary: Poly(, -caprolactone) (PCL) nanofibers with a dimension of about 150 nm were successfully fabricated by using a process of extruding PCL solution via a porous aluminium oxide template and then solidifying in methanol. The morphology, melting behavior and crystalline structure of the nanofibers were investigated by using scanning electron microscopy (SEM), differential scanning calorimetry (DSC) and X-ray diffraction (XRD). The results revealed that the weight-average molecular weight () of PCL hardly influenced the morphology of the nanofibers. However, the melting temperature (Tm) of the PCL crystalline increased slightly from 55.4 to 57.5,°C with an increase in . The accessional pressure and the presence of the porous template played an important role in the improvement of the orientation and crystallization structures of the polymer chains when they were passing through the nano-scale porous channel, leading to the conglomeration of the fiber and the much larger diameter than those from the pressure-induced extrusion process. Furthermore, comparing the processes with and without accessional pressure, the crystallinity of the nanofibers obtained under 0.2 MPa pressure increased, and the diffraction for the (001) lattice plane occurred. SEM image of PCL nanofibers extruded via a porous aluminium oxide template with the aid of pressure. [source] Synthesis and Molecular and Crystalline Structure of Polyfluoro-1,3-diazafluorenes.CHEMINFORM, Issue 43 2004V. M. Karpov No abstract is available for this article. [source] ChemInform Abstract: Novel Stereoselective Synthesis and Molecular and Crystalline Structure of 3-Allyl-4-(4-bromophenyl)-3-cyano-6-oxopiperidine-2-thione.CHEMINFORM, Issue 1 2002S. G. Krivokolysko Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a "Full Text" option. The original article is trackable via the "References" option. [source] Formation and ageing of L-glutamic acid spherulitesCRYSTAL RESEARCH AND TECHNOLOGY, Issue 7 2010R. Beck Abstract Polycrystalline spherulites of L-glutamic acid have been crystallized by pH-shift precipitation from stirred aqueous solutions. The time dependent behaviour of the spherulites has been studied during the crystallization process and batch filtration tests have been performed. It has been shown that the FBRM mean chord length of the investigated spherulites decreases in the course of time. The fact that the size reduction progresses faster at higher temperature and the solubility of resuspended polycrystalline particles decreasing with time, implies an ageing mechanism to be responsible for the observed changes in the particle size. It has been shown that the surface area decreases with time, ruling out particle breakage as a possible explanation for the decrease in particle size. XRD and Raman studies of L-glutamic acid, however, show only marginal differences in the crystalline structure of particles obtained from different time stages. The ageing may occur due to several different mechanisms like phase transformation and Ostwald ripening. L-glutamic acid spherulites after 3 h exhibit a 3-fold higher value for the cake resistance as compared to particles after 0.5 h. However, particles obtained after 22 h exhibit an 8-fold lower cake resistance as compared to the initially obtained spherulites, The increase in the cake resistance is attributed to the appearance of small plate-like crystals and a change in the interaction between the crystal surface and the solution. (© 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Effect of NaCl filler on ferroelectric phase and polaron configurations of PVDF filmsCRYSTAL RESEARCH AND TECHNOLOGY, Issue 4 2007I. S. ElashmawiArticle first published online: 8 MAR 200 Abstract Polyvinyldene fluoride (PVDF) films filled with NaCl of mass fraction range 1 , W , 6 % were prepared by casting technique. Their crystalline structure, thermal, optical properties and Electron spin resonance (ESR) were examined. X-ray diffraction (XRD) and differential thermal analysis (DTA) measurements indicated a maximum ferroelectric ,-phase increment at 4%. DTA was used to identify the phase transition temperatures, the order of reaction and the activation energy of melting. The UV-Visible optical absorption implied a minimum value of the estimated optical energy gap at W = 4%. ESR spectra contained a Lorentizian signal exhibiting a minimum value of the symmetry factor at W = 4%. The energy levels of the optical gap boundaries were though to contribute to ESR transitions. (© 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Mechanical activation of precursors for nanocrystalline materialsCRYSTAL RESEARCH AND TECHNOLOGY, Issue 1 2003H. Heegn Abstract Nanostructured materials win big scientific interest and increasingly economic meaning through their specific exceptional properties. Precursors that were compacted by pressing and sintering are normally used preparation of materials. In present work, the influence of mechanical activation by grinding on the structure as well as on compacting and sintering behavior of oxides from magnesium, aluminium and silicon has been investigated. Starting materials for each metal oxide differ in microstructure, dispersity, and porosity. The influence of mechanical activation on the destruction of crystalline structure to nanocrystalline, as well as to the amorphous stage and the compaction of powders with nano-particles, as well as structures with nanoscale pores have been compared. The possibilities of the consolidation of nanostructured materials were investigated. The mechanical activation took place in a disc vibration mill. The mechanical activated materials as well as their pressing and their sintering products were characterized by density, particle-sizedistribution, specific surface, pore-structure, microstructure, and crystallite size by X-ray powder diffraction (XRD). The mechanical activation of the model-substances led, in most cases, to an improvement of the compaction properties; thus, this improvement can be achieved with subsequent sintering densities up to 98% of the theoretical density. From these experiments, generalizations transferable to other materials can be made. [source] An Approach to the Synthesis of Silicon Carbide Nanowires by Simple Thermal Evaporation of Ferrocene onto Silicon WafersEUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 25 2007Jun-Jie Niu Abstract Scales of silicon carbide nanowires (SiC-NWs) with high quality were synthesized by direct thermal evaporation of ferrocene onto silicon wafers at high temperature. Ferrocene decomposed into iron and carbon, which was subsequently treated with silicon to form SiC-NWs at high temperature. The SiC-NWs possess small diameters of , 20 nm and lengths of several ,ms. Furthermore, the samples show a uniform morphology, crystalline structure, and a very thin oxide layer. The main crystal direction of [111] was confirmed by high-resolution field-emission-transmission electron microscopy (HR-FETEM). The Raman scattering spectra showed two peaks at , 796 (TO) and , 980 cm,1 (LO) with varying intensity ratios at different positions. The band line fluctuation was contributed to the Raman selection rules. With reference to the experimental results, we suggested a tentative growth model according to the vapor,liquid,solid (VLS) mechanism. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007) [source] Structural Evolution and Copper-Ion Release Behavior of Cu-pHEMA Hybrids Synthesized In Situ,ADVANCED ENGINEERING MATERIALS, Issue 11 2009Yen-Yu Liu Abstract A novel Cu-pHEMA hybrid was successfully prepared by in situ photopolymerization of 2-hydroxyethyl methacrylate (HEMA) monomer in the presence of Cu(II) copper ions, following an in situ chemical reduction. Experimental observations indicate that intermolecular interactions such as the coupling force and hydrogen bonding between the Cu and the hydroxyl groups further stabilize the hybrid structure to a considerable extent. Localization of the metallic copper particles within the pHEMA network structure as a result of those intermolecular interactions gives rise to the formation of discretely distributed nanocrystallites with particle sizes ranging from 5 to 25,nm in diameter. A crystallographic change of the Cu nanophase from an amorphous-like to a crystalline structure is observed as the H2O:HEMA molar ratio increases, upon synthesis, accompanied with an increase in the particle size. A relatively slow and sustained release of the Cu (in the form of cupric ions) from the hybrids was measured for a time period of about 10 days, which also illustrates a Cu(II)-induced proliferation of the endothelial cells over a relatively small range of release rate of the Cu from the hybrids. Such a new type of Cu-loaded hybrid hydrogel is expected to be compatible and may be considered as a candidate biomaterial for biomedical/therapeutic uses. [source] PIPD, a new high-modulus and high-strength polymer fibre with exceptional fire protection propertiesFIRE AND MATERIALS, Issue 4-5 2002M.G. Northolt The development of the new high-modulus and high-strength fibre M5, made of poly{2,6-diimidazo[4,5-b:4,,5, -e]-pyridinylene-1,4(2,5-dihydroxy)phenylene} or PIPD, has resulted in an organic polymer fibre with exceptional fire protection properties when compared with PBO, Twaron, Kevlar and Nomex fibres. The PIPD as-spun fibre with a modulus of 150 GPa and a tensile strength of 2.5 GPa is a crystal hydrate containing 21 wt% water. Cone calorimeter measurements yielded a fire performance index (FPI) 20 times higher than Nomex, with extremely low value for the specific extinction area (SEA) characterizing the smoke formation. The PIPD-HT fibre (recrystallized in an after treatment into the anhydrous crystalline structure) with a modulus >300 GPa and a strength >5 GPa has a FPI value similar to PBO but shows much less smoke formation than this fibre. Copyright © 2002 John Wiley & Sons, Ltd. [source] N,N -Dimethylformamide as a Reaction Medium for Metal Nanoparticle SynthesisADVANCED FUNCTIONAL MATERIALS, Issue 5 2009Isabel Pastoriza-Santos Abstract The versatility of wet chemical methods has rendered them extremely popular for the preparation of metal nanoparticles with tailored size and shape. This Feature Article reviews the use of N,N -dimethylformamide (DMF) for the reduction of metal salts, mainly Au and Ag, while also acting as a solvent. Apart from describing the ability of DMF to reduce metal salts, the effect of different parameters, such as the concentration of capping agent and metal precursors, the presence of preformed seeds acting as catalysts or their crystalline structure, on particle morphology are analyzed. Published reports on the use of different capping agents are summarized, with particular emphasis on the role of poly(vinylpyrrolidone) to determine the morphology of the particles. Finally, a brief overview is provided on the modulation of the optical response in DMF-based metal nanoparticle colloids with tunable size and shape. [source] Molecular dynamics and multiscale homogenization analysis of seepage/diffusion problem in bentonite clayINTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN ENGINEERING, Issue 12 2002Y. Ichikawa Abstract A scheme combining a molecular behaviour and macro-continuum phenomenon is presented for bentonite clay, which is a key component of a barrier system for disposal and containment of hazardous wastes. On designing a disposal facility we use a macro-phenomenological model. However the existing model is not sufficiently effective. Bentonite is a microinhomogeneous material. Properties of the saturated bentonite are characterized by montmorillonite and water, called montmorillonite hydrate. Since the crystalline structure of montmorillonite determines the fundamental properties of the montmorillonite hydrate, we analyse its molecular behaviour by applying a molecular dynamics simulation to enquire into the physicochemical properties of the montmorillonite hydrate such as diffusivity of chemical species. For extending the microscopic characteristics of constituent materials to a macroscopic diffusion behaviour of the microinhomogeneous material we apply a multiscale homogenization analysis, especially in order to treat micro-level of adsorption behaviour. Copyright © 2002 John Wiley & Sons, Ltd. [source] Nondestructive characterization of ferrofluids by wide-angle synchrotron light diffraction: crystalline structure and size distribution of colloidal nanoparticlesJOURNAL OF APPLIED CRYSTALLOGRAPHY, Issue 5 2008Alexei Vorobiev The combination of magnetic and nonmagnetic interactions between the colloidal particles in ferrofluids results in various local inter-particle correlations that, in turn, change the macroscopic properties of the whole system. Therefore, characterization of the particle ensemble is a crucial point, allowing optimization of a ferrofluid for a particular application. Here it is shown how the crystal structure of the particles can be easily obtained in a fast synchrotron light diffraction experiment without any special treatment of the ferrofluid sample. Moreover, from the same diffraction patterns, such important parameters as particle mean size and dispersion are retrieved; these are compared with the corresponding parameters obtained from electron microscopy data. A particular problem of magnetite,maghemite transformation in nanoparticles stabilized by the surfactant shell is pointed out. [source] Rotationally molded polyethylene: Structural characterization by x-ray and microhardness measurementsADVANCES IN POLYMER TECHNOLOGY, Issue 2 2001Maria Clara Cramez Rotationally molded polyethylene (PE) blended in two ways (turbo blending and extrusion) with nucleating and nonnucleating pigments is structurally characterized by wide- and small-angle x-ray scattering (WAXS and SAXS, respectively), DSC and microhardness measurements. Morphological observations are performed by polarized light microscopy. The melting temperature and the degree of crystallinity (from both DSC and WAXS) remain essentially constant regardless of sample preparation and type of pigment. The same holds for the crystal sizes from WAXS and the lamella thickness from SAXS. Only the values of microhardness depend on the type of pigment, increasing about 10% when a nucleating type is used. The almost constant values of these properties, contrasting to the spherulitic morphology, are explained by the fact that the processing conditions in rotational molding are very favorable for crystallization. As a consequence, optimal crystalline structure is achieved, which masks significantly the effect of pigments and blending conditions on the crystallization behavior of polyethylene. © 2001 John Wiley & Sons, Inc. Adv Polym Techn 20: 116,124, 2001 [source] Preparation and properties of dynamically cured PP/MAH- g -EVA/epoxy blendsJOURNAL OF APPLIED POLYMER SCIENCE, Issue 3 2009Xueliang Jiang Abstract A method concerning with the simultaneous reinforcing and toughening of polypropylene (PP) was reported. Dynamical cure of the epoxy resin with 2-ethylene-4-methane-imidazole (EMI-2,4) was successfully applied in the PP/maleic anhydride-grafted ethylene-vinyl acetate copolymer (MAH- g -EVA), and the obtained blends named as dynamically cured PP/MAH- g -EVA/epoxy blends. The stiffness and toughness of the blends are in a good balance, and the smaller size of epoxy particle in the PP/MAH- g -EVA/epoxy blends shows that MAH- g -EVA was also used as a compatibilizer. The structure of the dynamically cured PP/MAH- g -EVA/epoxy blends is the embedding of the epoxy particles by the MAH- g -EVA. The cured epoxy particles as organic filler increases the stiffness of the PP/MAH- g -EVA blends, and the improvement in the toughness is attributed to the embedded structure. The tensile strength and flexural modulus of the blends increase with increasing the epoxy resin content, and the impact strength reaches a maximum of 258 J/m at the epoxy resin content of 10 wt %. DSC analysis shows that the epoxy particles in the dynamically cured PP/MAH- g -EVA/epoxy blends could have contained embedded MAH- g -EVA, decreasing the nucleating effect of the epoxy resin. Thermogravimetric results show the addition of epoxy resin could improve the thermal stability of PP, the dynamically cured PP/MAH- g -EVA/epoxy stability compared with the pure PP. Wide-angle x-ray diffraction analysis shows that the dynamical cure and compatibilization do not disturb the crystalline structure of PP in the blends. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009 [source] Properties of soy protein isolate/poly(vinyl alcohol) blend "green" films: Compatibility, mechanical properties, and thermal stabilityJOURNAL OF APPLIED POLYMER SCIENCE, Issue 6 2008Jun-Feng Su Abstract Blend films from nature soy protein isolates (SPI) and synthetical poly(vinyl alcohol) (PVA) compatibilized by glycerol were successfully fabricated by a solution-casting method in this study. Properties of compatibility, mechanical properties, and thermal stability of SPI/PVA films were investigated based on the effect of the PVA concentration. XRD tests confirm that the SPI/PVA films were partially crystalline materials with peaks of 2, = 20°. And, the addition of glycerol will insert the crystalline structure and destroy the blend microstructure of SPI/PVA. Differential scanning calorimetry (DSC) tests show that SPI/PVA blend polymers have a single glass transition temperature (Tg) between 80 and 115.0°C, which indicate that SPI and PVA have good compatibility. The tension tests show that SPI/PVA films exhibit both higher tensile strength (,b) and percentage elongation at break point (P.E.B.). Thermogravimetric analysis (TGA) and water solubility tests show that SPI/PVA blend polymer has more stable stability than pure SPI. All the results reflect that SPI/PVA/glycerol blend film provides a convenient and promising way to prepare soy protein plastics for practical application. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008 [source] Surface modification of starch nanocrystals through ring-opening polymerization of ,-caprolactone and investigation of their microstructuresJOURNAL OF APPLIED POLYMER SCIENCE, Issue 4 2008Hassan Namazi Abstract Bionanoparticles of starch obtained by submitting native potato starch granules to acid hydrolysis conditions. The resulted starch nanoparticles were used as core or macro initiator for polymerization of ,-caprolactone (CL). Starch nanoparticle- g -polycaprolactone was synthesized through ring-opening polymerization (ROP) of CL in the presence of Sn(Oct)2 as initiator. The detailed microstructure of the resulted copolymer was characterized with NMR spectroscopy. Thermal characteristic of the copolymer was investigated using DSC and TGA. By introducing PCL, the range of melting temperature for starch was increased and degradation of copolymer occurred in a broader region. X-ray diffraction and TEM micrographs confirmed that there was no alteration of starch crystalline structure and morphology of nanoparticles, respectively. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008 [source] Relationship between the crystalline structure and mechanical behavior in isotropic and oriented polyamide 12JOURNAL OF APPLIED POLYMER SCIENCE, Issue 1 2008Nadya Dencheva Abstract This study reports on the relationship between the crystalline structure and mechanical behavior of differently processed and annealed polyamide 12 (PA12) samples. Two sets of samples were obtained: isotropic PA12 films prepared by hot pressing and oriented cables prepared by consecutive extrusion and cold drawing. These samples were isothermally annealed in the range of 80,160°C and then subjected to tensile tests at room temperature. A combination of solid-state 13C-NMR and synchrotron wide- and small-angle X-ray scattering was used to obtain reliable structural data from these samples before and after the tensile tests. These structural data were related to the mechanical properties of the respective PA12 samples. Deformation models explaining all the experimental results were suggested for the different PA12 samples. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008 [source] Polymer nanocomposites based on needle-like sepiolite clays: Effect of functionalized polymers on the dispersion of nanofiller, crystallinity, and mechanical propertiesJOURNAL OF APPLIED POLYMER SCIENCE, Issue 2 2008E. Bilotti Abstract Polypropylene (PP)/sepiolite (Sep) nanocomposites are prepared by melt compounding in a mini-extruder apparatus. The often used maleic anhydride-modified polypropylene (PP-g-MA) is compared with two custom-made functionalized polymers, PP-acid and the di-block copolymer PP-PEO, with respect to the filler dispersion and filler reinforcement efficiency. For that purpose, morphological and mechanical studies are carried out by means of scanning electron microscopy (SEM), transmission electron microscopy (TEM), and mechanical tensile tests. In addition, the nanocomposites are characterized by wide-angle X-ray scattering (WAXS) and differential scanning calorimetric (DSC) techniques, to assess the effect of the nanofiller on the crystalline structure of the PP matrix nano-filler. The use of PP-PEO and PP-acid resulted in a better nanofiller dispersion compared with traditional PP-g-MA-modified systems. Sepiolite acts as nucleating agent for the crystallization of PP and seems to lead to an orientation of the ,-phase crystals. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2008 [source] Electrical behavior of polyurethane composites with acid treatment-induced damage to multiwalled carbon nanotubesJOURNAL OF APPLIED POLYMER SCIENCE, Issue 1 2007Pill Gyu Jang Abstract We have studied the electrical conductivity and percolation threshold of polyurethane (PU) composites filled with multiwalled carbon nanotubes (MWCNT) purified by increasing immersion time in aqueous solutions of either nitric acid or a mixture of nitric and sulfuric acids at 80°C. The MWCNT crystallinity peaks after 2 h of treatment, which enables the PU composites to enhance the percolation threshold and electrical conductivity in the conductive network formation region. MWCNT treated under either a milder or severer acidic condition deteriorate the electrical behavior of the composites, since MWCNT are poorly dispersed in the PU matrix in the former condition, but lost their intrinsic electrical conductivity due to the partial destruction of their crystalline structure in the latter. Therefore, the acid treatment needs to be carefully controlled to effectively purify the MWCNT, maintain the crystalline structure without further damage, and thereby improve the electrical behavior of PU/MWCNT composites. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007 [source] Structure modification of isotactic polypropylene through chemical crosslinking: Toughening mechanismJOURNAL OF APPLIED POLYMER SCIENCE, Issue 5 2007S. Bouhelal Abstract Reversibly crosslinked isotactic polypropylene (iPP) was prepared in the presence of dicumyl peroxide. The effects of the peroxide oxy-radicals in the melt were investigated in relation to the modification of the polymer. The dynamic rheology analysis of the crosslinking process was carried out by using a plastograph. The crosslinking reaction was evaluated by the Monsanto method. The resulting structure of the modified samples was studied by means of differential scanning calorimetry (DSC), wide-angle X-ray scattering (WAXS), microhardness, and mechanical properties. The degree of crystallinity of the modified iPP, derived from DSC and WAXS, remains almost unchanged, i.e., the crystalline structure is unaffected, though the lamellar thickness slightly decreases. The impact strength of the crosslinked iPP is greatly improved with reference to that of the unmodified material. A transition from brittle to ductile behavior appears in the modified iPP for all the crosslinking agents studied. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 2968,2976, 2007 [source] The influence of thermal treatment on the mechanical characteristics of a PLLA coiled stentJOURNAL OF BIOMEDICAL MATERIALS RESEARCH, Issue 1 2009Tré R. Welch Abstract We studied the effects of thermal treatment on the expansive characteristics of a coil-within-coil Poly(L -lactic acid) (PLLA) fiber stent developed at our institution to improve its mechanical performance and reproducibility. Following fabrication, furled stents were thermally treated at 62°C for 25 min. The mechanical characteristics were measured compared with those of untreated stents when both were expanded via sequential balloon catheter pressure loading up to 12 atm. Treated stents reached full diameter at 3 atm and maintained that diameter despite further pressure increases. Using measurements of pressure, diameter, and axial length, we calculated the sequential mechanical work required to unfurl the stent. The mechanical work for complete unfurling of treated stents was significantly less than that required for untreated controls. Little axial dimensional change was observed for treated stents. Treated stents exhibited higher stiffness than controls at all pressure levels and also demonstrated higher resistance to external pressure-induced collapse, as measured in a special apparatus developed in our laboratory. Differential scanning calorimetry measurements indicated higher crystallinity values for fibers used in treated stents compared with controls. SEM examination of striations revealed that treated stents underwent less twist than controls following balloon-induced unfurling. The results indicate that, thermal treatment improves the reorientation and realignment of fiber crystalline structure, and favorably influences on the fiber stress-strain behavior and the expansive mechanical characteristics of the PLLA fiber stents. © 2008 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 2009 [source] Microarchitectural and Physical Changes During Fetal Growth in Human Vertebral Bone,JOURNAL OF BONE AND MINERAL RESEARCH, Issue 4 2003S Nuzzo Abstract The ossification process in human vertebra during the early stage of its formation was studied by X-ray diffraction (XRD) and X-ray microtomography (,CT) at the European Synchrotron Radiation Facility (ESRF), Grenoble, France. Twenty-two samples taken from vertebral ossification centers of human fetal bone (gestational age ranging between 16 and 26 weeks) were investigated. The analysis of three-dimensional images at high spatial resolution (,10 and ,2 ,m) allows a detailed quantitative description of bone microarchitecture. A denser trabecular network was found in fetal bone compared with that of adult bone. The images evidenced a global isotropic structure clearly composed of two regions: a central region (trabecular bone) and a peripheral region (immature bone). XRD experiments evidenced hydroxyapatite-like crystalline structure in the mineral phase at any fetal age after 16 weeks. Interestingly, the analysis of XRD patterns highlighted the evolution of crystalline structure of mineralized bone as a function of age involving the growth of the hydroxyapatite crystallites. [source] Chemical Structure and Physical Properties of Mung Bean Starches Isolated from 5 Domestic CultivarsJOURNAL OF FOOD SCIENCE, Issue 9 2007S.-H. Kim ABSTRACT:, Chemical structure and physical properties of starches isolated from 5 domestic mung bean cultivars (Gyungsun, Geumsung, Sunhwa, Eohul, and Jangan) were examined. The granules were jelly bean like in shape and smooth on surface, and the size was within 10 to 30 ,m. Mung bean starches displayed a CA -type crystalline structure when judged by the X-ray diffraction patterns. Branch chain-length distribution patterns of amylopectin (AP) revealed that peak chain length of APs was at either DP (degree of polymerization) 12 or DP13. Apparent amylose contents of 5 cultivars by iodine affinity test were 31.7% to 33.8%. Mung bean APs showed a unique molecular size distribution that has not been observed from other plant-derived starches. Two distinct peaks of AP fraction were identified on the size-exclusion chromatogram, and the ratios of these 2 peaks were different depending on the mung bean cultivars. Weight-average chain length (CLavg) of APs was in the range of 16.9 (Eohul) and 17.5 (Geumsung). The onset temperature (To) and enthalpy change (,Hgel) of starch gelatinization were 54.6 to 60.2 °C and 11.6 to 13.2 J/g. The ,H of the retrograded mung bean starches was 5.5 to 6.6 J/g, which indicated 44.5% to 52.7% of recrystallization. The pasting temperature, peak viscosity, and setback were 66.1 to 69.2 °C, 510 to 579 Rapid Visco Unit (RVU), and 66 to 90 RVU, respectively. [source] A fine match between the stereoselective ligands and membrane pore size for enhanced chiral separationAICHE JOURNAL, Issue 9 2009Honglei Wang Abstract A D,L -tryptophan separation factor of 12,15 and D -tryptophan yield of >95% have been successfully achieved through using human serum albumin (HSA) as the stereoselective ligand in an affinity ultrafiltration (UF) system. The obtained separation factor in this work is even higher than the intrinsic value of 8.5 of HSA. This synergism may arise from the fact that a fine match between the regular crystalline structure of HSA molecules and suitable pore size of membranes makes some HSA molecules be retained within the membrane cross-section, thus offering a second-stage binding opportunity for L -tryptophan molecules. Therefore, a simultaneous enhancement in separation factor and D -tryptophan yield has been fulfilled in this work. The feasibility of HSA regeneration after D,L -tryptophan separation has also been demonstrated through a series of pH adjustment experiments. This study reveals the applicability of HSA in affinity UF systems for chiral separation due to economization of material costs. © 2009 American Institute of Chemical Engineers AIChE J, 2009 [source] Solid lipid nanoparticles (SLN) as carriers for the topical delivery of econazole nitrate: in-vitro characterization, ex-vivo and in-vivo studiesJOURNAL OF PHARMACY AND PHARMACOLOGY: AN INTERNATI ONAL JOURNAL OF PHARMACEUTICAL SCIENCE, Issue 8 2007Vanna Sanna Solid lipid nanoparticles (SLN) designed for topical administration of econazole nitrate (ECN), were prepared by o/w high-shear homogenization method using different ratios of lipid and drug (5:1 and 10:1). SLN were characterized in terms of particle size, morphology, encapsulation efficiency and crystalline structure. After incorporation of SLN into hydrogels, rheological measurements were performed, and ex-vivo drug permeation tests were carried out using porcine stratum corneum (SC). In-vivo study of percutaneous absorption of ECN as a function of application time and composition of gels was carried out by tape-stripping technique. Penetration tests of the drug from a conventional gel were performed as comparison. High-shear homogenization method resulted in a good technique for preparation of ECN-loaded SLN. Particles had a mean diameter of about 150 nm and a regular shape and smooth surface. The encapsulation efficiency values were about 100%. Ex-vivo tests showed that SLN were able to control the drug release through the SC; the release rate depended upon the lipid content on the nanoparticles. In-vivo studies demonstrated that SLN promoted a rapid penetration of ECN through the SC after 1 h and improved the diffusion of the drug in the deeper skin layers after 3 h of application compared with the reference gel. [source] Organic,inorganic hybrid brushes consisting of macrocyclic oligomeric silsesquioxane and poly(,-caprolactone): Synthesis, characterization, and supramolecular inclusion complexation with ,-cyclodextrinJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 24 2009Jin Han Abstract Organic,inorganic hybrid brushes comprised of macrocyclic oligomeric silsesquioxane (MOSS) and poly(,-caprolactone) (PCL) were synthesized via the ring-opening polymerization of ,-caprolactone (CL) with cis- hexa[(phenyl) (2-hydroxyethylthioethyldimethylsiloxy)]cyclohexasiloxane as the initiator. The MOSS macromer bearing hydroxyl groups was synthesized via the thiol-ene radical addition reaction between cis -hexa[(phenyl)(vinyldimethylsiloxy)]cyclohexasiloxane and ,-mercaptoethanol. The organic,inorganic PCL cyclic brushes were characterized by means of nuclear magnetic resonance spectroscopy (NMR) and gel permeation chromatography (GPC). These MOSS,PCL brushes were then used to prepare the supramolecular inclusion complexes with ,-cyclodextrin (,-CD). The X-ray diffraction (XRD) indicates that the organic,inorganic inclusion complexes (ICs) have a channel-type crystalline structure. It is noted that the molar ratios of CL unit to ,-CD for the organic,inorganic ICs are quite dependent on the lengths of the PCL chains bonded to the silsesquioxane macrocycle. While the PCL chains were short, the efficiency of inclusion complexation was significantly decreased. The decreased efficiency could be attributed to the repulsion of the adjacent PCL chains bonded to the silsesquioxane macrocycle and the restriction of the bulky silsesquioxane macrocycle on the motion of PCL chains; this effect is pronounced with decreasing the length of the PCL chains. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2009 [source] Preparation of novel poly(ethylene oxide- co -glycidol)-graft-poly(,-caprolactone) copolymers and inclusion complexation of the grafted chains with ,-cyclodextrinJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 11 2006Juan Huang Abstract A well-defined comblike copolymer of poly(ethylene oxide- co -glycidol) [(poly(EO- co -Gly)] as the main chain and poly(,-caprolactone) (PCL) as the side chain was successfully prepared by the combination of anionic polymerization and ring-opening polymerization. The glycidol was protected by ethyl vinyl ether to form 2,3-epoxypropyl-1-ethoxyethyl ether (EPEE) first, and then ethylene oxide was copolymerized with EPEE by an anionic mechanism. The EPEE segments of the copolymer were deprotected by formic acid, and the glycidol segments of the copolymers were recovered after saponification. Poly(EO- co -Gly) with multihydroxyls was used further to initiate the ring-opening polymerization of ,-caprolactone in the presence of stannous octoate. When the grafted copolymer was mixed with ,-cyclodextrin, crystalline inclusion complexes (ICs) were formed, and the intermediate and final products, poly(ethylene oxide- co -glycidol)- graft -poly(,-caprolactone) and ICs, were characterized with gel permeation chromatography, NMR, differential scanning calorimetry, X-ray diffraction, and thermogravimetric analysis in detail. The obtained ICs had a channel-type crystalline structure, and the ratio of ,-caprolactone units to ,-cyclodextrin for the ICs was higher than 1:1. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 3684,3691, 2006 [source] Gradient graft copolymers derived from PEO-based macromonomersJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 4 2006Dorota Neugebauer Abstract Atom transfer radical polymerization (ATRP) of two poly(ethylene oxide) (PEO) macromonomers, with different polymerization degrees (DPn) and different end groups, was conducted in solution via the grafting through method. Selection of a PEO methacrylate with a methyl end-group (PEOMeMA, DPPEO = 23) and a PEO acrylate end-capped by a phenyl ring (PEOPhA, DPPEO = 4) for the copolymerization led to a spontaneous gradient of PEO grafts along the copolymer backbone. Such a composition was formed because of significantly different reactivities of the two PEO macromonomers. The resulting copolymer has PEOMeMA at one end of the polymer chain, gradually changing through hetero-sequences of PEOPhA at the other chain end. An increase in the initial feed ratio of PEO acrylate reduced the rate of change in the shape of the gradient. Amorphous,crystalline structure in the copolymers was demonstrated by DSC and WAXS. The mechanical measurements of copolymers consisting of an amorphous PEOPhA and crystallizable PEOMeMA segments indicated elastomeric properties in the range of a soft rubber (G, , 104 Pa, G, , G,). © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 1347,1356, 2006 [source] Conductivity and characterization of polyurea electrolytes with carboxylic acidJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 24 2003Shao-Ming Lee Abstract Polyurea, which was synthesized from 4,4,-diphenylmethane diisocyanate, Jeffamine-ED2001 (weight-average molecular weight: 2000), and 3,5-diaminobanzoic acid (DABA) were doped with lithium perchlorate (LiClO4) as the polyelectrolyte. Differential scanning calorimetry (DSC), Fourier transform infrared (FTIR) spectroscopy, and 7Li magic-angle spinning (MAS) solid-state NMR were used to monitor changes in the morphology of polyurea electrolytes corresponding to the concentration of LiClO4 dopants. DSC showed the glass-transition temperature of the hard and soft segments increases with salt concentration. FTIR indicated the carboxylic group of DABA coordinates with the Li+ ion, and the ordered hydrogen-bonded urea carbonyl groups are destroyed when the salt concentration exceeds 0.5 mmole of LiClO4 (gPUrea),1. The 7Li MAS solid-state NMR investigation of the polyurea electrolytes revealed the presence of two Li+ environments at lower temperature. Impedance spectroscopy measurements showed that the conductivity behavior followed the Arrhenius equation, and the maximum conductivity occurred when the crystalline structure of polyurea was disrupted. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 4007,4016, 2003 [source] Synthesis and structure of wholly aromatic liquid,crystalline polyesters containing meta- and ortholinkagesJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 8 2001Chaobin He Abstract Wholly aromatic main-chain rigid-chain polymers containing meta- and orthokink linkages were synthesized. The thermal property, liquid crystallinity, and crystalline structure were studied using DSC, polarized light microscopy, and wide-angle X-ray scattering. These polymers exhibited liquid crystallinity up to 50 mol % of meta- and orthokink linkages. The existence of liquid crystallinity in these polymers may be attributed to the adoption of cis conformation in kink units in these polymers because the energy penalty for doing so can be compensated by the formation of the liquid,crystalline phase. The crystallinity of the polymers was low, and the crystal structure was quite similar to that of the pure polymers (without kink units). This can be explained by that fact that the crystal region mainly consists of the nonkink units, and the kink units disrupt the crystallization of the polymers and form defects. © 2001 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 39: 1242,1248, 2001 [source] | ||||||||||||||||||||||||||||||||||||||||