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Melting Behavior (melting + behavior)
Selected AbstractsMelting behavior and crystallization kinetics of sulfonated poly(butylene isophthalate)POLYMER ENGINEERING & SCIENCE, Issue 7 2002Nadia Lotti The melting behavior and the crystallization kinetics of sulfonated poly(butylene isophthalate) random copolymers were investigated by means of differential scanning calorimetry. The multiple endotherms, commonly observed in polyesters, were found to be influenced both by composition and crystallization temperature. By applying the Hoffman-Weeks method, the equilibrium melting temperatures of the copolymers under investigation were obtained. The presence of a crystal-amorphous interphase was evidenced and its amount was found to increase as the sulfonated unit content was increased. Isothermal melt crystallization kinetics of the sample containing the lowest amount of sulfonated units was analyzed according to the Avrami treatment. The introduction of such units was found to decrease the overall crystallization rate of poly(butylene isophthalate). Values of Avrami's exponent n close to 3 were obtained, independently of crystallization temperature, in agreement with a crystallization process originating from predetermined nuclei and characterized by three-dimensional spherulitic growth. [source] Effects of hydrogenation parameters on trans isomer formation, selectivity and melting properties of fatEUROPEAN JOURNAL OF LIPID SCIENCE AND TECHNOLOGY, Issue 3 2008Anar Musavi Abstract Effects of hydrogenation conditions (temperature, hydrogen pressure, stirring rate) on trans fatty acid formation, selectivity and melting behavior of fat were investigated. To this aim, soybean oil was hydrogenated under various conditions and fatty acid composition, trans isomer formation, slip melting point (SMP), solid fat content (SFC) and iodine number (IV) of the samples withdrawn at certain intervals of the reactions were monitored. A constant ratio (0.03%) of Nysosel 222 was used in the various combinations of temperature (150, 165 and 180,°C), stirring speed (500, 750 and 1000,rpm) and hydrogen pressure (1, 2 and 3,bar). Raising the temperature increased the formation of fatty acid isomers, whereas higher stirring rates decreased this formation, while changes in hydrogen pressure had no effect or slightly reduced it, depending on other parameters. Results also indicated that the trans fatty acid ratio increased with IV reduction, reached the highest value when the IV was about 70 and decreased at IV < 70 due to saturation. Selectivity values (S21) at that point ranged between 5.78 and 11.59. Lower temperatures and higher stirring rates decreased not only the trans isomer content but also the S21 values at significant levels. However, same effects were not observed with the changes in hydrogen pressure. It was determined that a high SMP does not necessarily mean a high SFC. Selective conditions produced samples with higher SFC but lower SMP, which is possibly because of higher trans isomer formation as well as lower saturation. [source] An experimental study of single-screw extrusion of HDPE,wood compositesADVANCES IN POLYMER TECHNOLOGY, Issue 3 2010Karen Xiao Abstract Single-screw extrusion experiments were carried out to study the extrusion characteristics of HDPE,wood composites. Three screw geometries (A, B, and C) were used, and the effects of screw speed on output, melting, and pressure profile were studied. Screw A had a much higher compression ratio than screws B and C, which directly affected the melting behavior of the polymers. Screws B and C had the same compression ratio; however, screw C had the same metering capacity as screw A. Therefore, by comparing screws B and C, the effect of feed depth on the solid conveying capacity was investigated. It was found that while screw B had higher outputs than both screws A and C as expected, screw C had a much lower output than screw A for highly filled resins even though they had the same metering capacity. For HDPE, screws A and C showed the same output as expected. Further examinations of the pressure profiles and melting profiles from screw extraction experiments confirmed that screw C showed a severely starved solids conveying capacity for wood-filled resins, which limited the total outputs. Comparing the outputs and pressure generations between theoretical predictions and actual experimental results, it was evident that due to the inaccurate assumption of fully filled channels common in single screw extrusion, both outputs and pressure generations in the extruders were overpredicted. © 2010 Wiley Periodicals, Inc. Adv Polym Techn 29:197,218, 2010; View this article online at wileyonlinelibrary. DOI 10.1002/adv.20190 [source] Physical characterization of starch extrudates as a function of melting transitions and extrusion conditionsADVANCES IN POLYMER TECHNOLOGY, Issue 4 2004Stéphanie Blanche Abstract The objective of this study was to investigate the relationships between starch melt transition characteristics, extrusion conditions, and final product properties. Cornstarch was extruded using a corotating twin-screw extruder at varying moisture content, medium/high screw configuration, and 300/400-rpm screw speeds. Extrudates were evaluated for bulk density, expansion ratio, cell structure, bending strength, thermal and pasting properties. Temperature change (,T) was defined as the temperature difference between the native starch melting temperature and its melt temperature just behind the die during extrusion at a given moisture content. ,T was significantly affected by starch moisture content and mechanical shearing, which controlled the melting behavior of the starch in the barrel. Amylose,lipid complex formation during extrusion increased as ,T increased and leveled off at ,T of about 20°C. Pasting peak viscosity of the starch extrudates decreased as ,T increased and leveled off at ,T of about 15°C. Within the same range of mechanical shearing intensity, extrudate bulk density and bending strength decreased linearly as ,T increased. Extrudate expansion was negatively correlated to bulk density. © 2004 Wiley Periodicals, Inc. Adv Polym Techn 23: 277,290, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/adv.20017 [source] Crystallization and melting behavior of HDPE in HDPE/teak wood flour composites and their correlation with mechanical propertiesJOURNAL OF APPLIED POLYMER SCIENCE, Issue 4 2010Kamini Sewda Abstract The nonisothermal crystallization behavior and melting characteristics of high-density polyethylene (HDPE) in HDPE/teak wood flour (TWF) composites have been studied by differential scanning calorimetry (DSC) and wide angle X-ray diffraction (WAXD) methods. Composite formulations of HDPE/TWF were prepared by varying the volume fraction (,f) of TWF (filler) from 0 to 0.32. Various crystallization parameters evaluated from the DSC exotherms were used to study the nonisothermal crystallization behavior. The melting temperature (Tm) and crystallization temperature (Tp) of the composites were slightly higher than those of the neat HDPE. The enthalpy of melting and crystallization (%) decrease with increase in the filler content. Because the nonpolar polymer HDPE and polar TWF are incompatible, to enhance the phase interaction maleic anhydride grafted HDPE (HDPE-g-MAH) was used as a coupling agent. A shift in the crystallization and melting peak temperatures toward the higher temperature side and broadening of the crystallization peak (increased crystallite size distribution) were observed whereas crystallinity of HDPE declines with increase in ,f in both DSC and WAXD. Linear correlations were obtained between crystallization parameters and tensile and impact strength. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010 [source] Effect of wood flour loading and thermal annealing on viscoelastic properties of poly(lactic acid) composite filmsJOURNAL OF APPLIED POLYMER SCIENCE, Issue 3 2010M. Hrabalova Abstract Poly(lactic acid) (PLA) films filled with up to 50 wt % softwood flour were prepared by melt compounding and thermocompression. Thermal annealing of the melt was performed at temperatures from 90°C to 120°C, for 45 min. Responses on polymer-filler interactions, viscoelastic properties, crystallinity of PLA as well as PLA-wood flour-filled films were investigated by differential scanning calorimetry (DSC), dynamic mechanical analysis (DMA), and scanning electron microscopy (SEM). The effectiveness of fillers on the storage moduli (C) was also calculated. The results reveal that wood flour (WF) in conjunction with thermal annealing affected the melting behavior of PLA matrix, and the glass transition temperature. It was further found that the effectiveness of the wood filler in biocomposites widely improved with thermal annealing as well as with higher WF concentration. Finally, it was found that the compatibility between WF and the PLA matrix can be improved when suitable annealing conditions are applied. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010 [source] Amorphous orientation and its relationship to processing stages of blended polypropylene/polyethylene fibersJOURNAL OF APPLIED POLYMER SCIENCE, Issue 6 2008Amy M. Trottier Abstract Changes in the molecular orientation, melting behavior, and percent crystallinity of the individual components in a fibrous blend of isotactic polypropylene (iPP) and high-density polyethylene (HDPE) that occur during the melt extrusion process were examined using wide-angle X-ray diffraction (WAXD) and differential scanning calorimetry (DSC). The crystalline orientation of each component was found using Wilchinsky's treatment of uniaxial orientation and described by the Hermans,Stein orientation parameter. The amorphous orientation was found by resolving the X-ray diffraction pattern in steps of the azimuthal angle into its iPP and HDPE crystalline and amorphous reflections. The utility of DSC and WAXD analyses to capture the effects of small differences in processing, and the use of these results as fingerprints of a particular manufacturing process were demonstrated. Major increases in the melting temperatures, percent crystallinities, and molecular orientations of the iPP and HDPE components occurred during the main stretching stage of the melt extrusion process. The annealing stage was found to have little to no effect on the melting behavior and molecular orientation of these components. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008 [source] Effect of ,-nucleating agents on crystallization and melting behavior of isotactic polypropyleneJOURNAL OF APPLIED POLYMER SCIENCE, Issue 5 2008Wenchang Xiao Abstract Two kinds of ,-nucleating agents, named a rare earth complex (WBG) and a N,N,-dicyclohexylterephthalamide (TMB5), were introduced into isotactic polypropylene (iPP), and their effect on crystallization and melting behavior of iPP was comparatively investigated. Wide angle X-ray diffraction measurements revealed that both the two additives were highly effective in inducing , modification. At their respective optimum concentrations of 0.08 wt % for WBG and 0.06 wt % for TMB5, the relative amount of ,-form calculated by Turner-Jones equation both exceeds 92%. However, the isothermal crystallization kinetics investigated by differential scanning calorimetry demonstrated that WBG had more pronounced effect than TMB5 in accelerating the overall crystallization rate. The Lauritzen,Hoffman theory analysis also revealed that WBG was more effective not only in increasing the nucleus number but also in accelerating the growth rate of crystallization. After completing isothermal crystallization process, the subsequent melting behavior examination suggested that the addition of WBG expanded the upper limit temperature of forming , modification, and therefore was more effective in delaying the ,-, transformation than TMB5. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008 [source] Isothermal crystallization kinetics and melting behaviors of nanocomposites of poly(trimethylene terephthalate) filled with nano-CaCO3JOURNAL OF APPLIED POLYMER SCIENCE, Issue 3 2007Mingtao Run Abstract The isothermal crystallization and subsequent melting behavior of poly(trimethylene terephthalate) (PTT) composites filled with nano-CaCO3 were investigated at designated temperatures with differential scanning calorimetry. The Avrami equation was used to fit the isothermal crystallization. The Avrami exponents were determined to be 2,3 for the neat PTT and PTT/CaCO3 composites. The particles of nano-CaCO3, acting as nucleating agents in the composites, accelerated the crystallization rate, with the half-time of crystallization decreasing or the growth rate constant (involving both nucleation and growth rate parameters) increasing. The crystallization activation energy calculated from the Arrhenius formula was reduced as the nano-CaCO3 content increased from 0 to 2%, and this suggested that nano-CaCO3 made the molecular chains of PTT easier to crystallize during the isothermal crystallization process. Subsequent melting scans of the isothermally crystallized composites exhibited triple or double melting endotherms: the greater the content was of nano-CaCO3, the lower the temperature was of the melting peak. The degree of crystallization deduced from the melt enthalpy of composites with the proper concentration of nano-CaCO3 was higher than that of pure PTT, but it was lower when the nano-CaCO3 concentration was more than 2%. The transmission electron microscopy pictures suggested that the dispersion state of nano-CaCO3 particles in the polymer matrix was even when its concentration was no more than 2%, whereas some agglomeration occurred when its concentration was 4%. Polarized microscopy pictures showed that much smaller or less perfect crystals formed in the composites because of the interaction between the molecular chains and nano-CaCO3 particles. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2007 [source] Phase Equilibrium in the Fluorapatite,Anorthite,Diopside SystemJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 12 2000Dilshat Ubaydullayevich Tulyaganov The binary systems Ca5[PO4]3F,CaAl2Si2O8 and Ca5[PO4]3F,CaMgSi2O6 have been investigated, via annealing and quenching in the experimental method, direct observation of the melting behavior of the samples, X-ray diffraction analysis, petrography, and transmission electron microscopy. Phase equilibrium in the ternary system Ca5[PO4]3F,CaAl2Si2O8,CaMgSi2O6 was determined by combining information from the structure of the binary boundary systems and additional experimental data that were obtained from ternary compositions. The glass-formation region of the fluorapatite,anorthite,diopside system was studied, and the glass compositions for the development of glass-ceramics for technical and medical applications were identified. [source] Cover Picture: Laser Phys.LASER PHYSICS LETTERS, Issue 7 2010Lett. It's known that single crystals of germanate melilites, such as Ba2ZnGe2O7 and Sr2MgGe2O7, show a congruent melting behavior at about 1450 °C. Crystals of Sr2MgGe2O7 were grown from melt of stoichiometric composition by the Czochralski technique using a seed crystal orientation (and pulling direction) along [001], a pulling velocity of 2,3 mm/h and crystal rotation of 40,60 rad/min. For single crystal growth of Ba2ZnGe2O7 a melt with a surplus of ,4 wt.% BaO and ,5 wt.% GeO2 proved to be useful. Grown crystals are of dimensions up to 25 mm in length and 18 mm in diameter for Sr2MgGe2O7 and of up to 15 mm in length and in diameter for Ba2ZnGe2O7. In Cover picture an example of a grown crystal of Sr2MgGe2O7 is presented. (Cover picture: A.A. Kaminskii, L. Bohatý, et al., pp. 528,543, in this issue) (© 2010 by Astro Ltd., Published exclusively by WILEY-VCH Verlag GmbH & Co. KGaA) [source] Functionalization of LDPE by Melt Grafting with Glycidyl Methacrylate and Reactive Blending with Polyamide-6MACROMOLECULAR CHEMISTRY AND PHYSICS, Issue 8 2003Qian Wei Abstract Low-density polyethylene (LDPE) was functionalized by melt radical grafting with glycidyl methacrylate (GMA) and employed for reactive blending with polyamide-6 (PA6). The effect of the reaction procedure on the grafting degree of LDPE- g -GMA samples (0.5,12.5 wt.-% GMA) was analyzed as a function of the concentration of GMA monomer, radical initiator (BTP), and addition of styrene as co-monomer. Optimized grafting conditions were obtained when the amount of the monomer is below 10 wt.-% and that of peroxide in the range 0.2,0.4 wt.-%. Binary blends of PA6 with LDPE- g -GMA (3.5 wt.-% GMA) and with LDPE at various compositions (80/20, 67/33, 50/50 wt.-%) were prepared in an internal mixer and their properties were evaluated by torque, SEM and DSC analyses. Morphological examination by SEM showed a large improvement of phase dispersion and interfacial adhesion in PA6/LDPE- g -GMA blends as compared with PA6/LDPE blends. The average diameter of dispersed polyolefin particles was about 0.4 ,m for LDPE- g -GMA contents <,50 wt.-%. A marked increase of melt viscosity was observed for the compatibilized blends depending on the concentration of grafted polyolefin, and it was accounted for by the reaction between the epoxy groups of GMA and the carboxyl/amine end-groups of PA6. The variation of torque was thus related to the molar ratio of reactive group concentration. The analysis of crystallization and melting behavior pointed out marked differences in the phase structure of the blends due to the presence of the functionalized polyolefin. Finally, the in situ formation of a graft copolymer between LDPE- g -GMA and PA6 was investigated by means of a selective dissolution method (Molau test) and by FT-IR and DSC analyses. SEM micrograph of fracture surface of PA6/LDPE- g -GMA 50/50 blend. [source] Effect of zirconium dioxide on crystallization and melting behavior of flame sprayed polyamide 1010POLYMER COMPOSITES, Issue 4 2008Yadong Li The crystallization and melting behavior of flame sprayed Polyamide 1010 (PA1010) containing zirconium dioxide (ZrO2) were investigated using differential scanning calorimeter (DSC). ZrO2 has a heterogenous nucleation effect on PA1010, leading to a moderate increase in the crystallization temperature and a decrease in the supercooling temperature. A modified Avrami theory could be successfully used to well describe the early stages of non-isothermal crystallization of PA1010 and its composite coatings. A study of the nucleation activity, which indicated the influence of the filler on the polymer matrix, revealed that the zirconium dioxide nanoparticles had a good nucleation effect on PA1010. POLYM. COMPOS., 2008. © 2008 Society of Plastics Engineers. [source] Crystallization and melting behavior of zenite thermotropic liquid crystalline polymers,POLYMER ENGINEERING & SCIENCE, Issue 2 2002K. P. Pramoda The crystallization and melting behavior of a DuPont ZeniteTM series, namely, Z 6000 and Z 8000B, thermotropic liquid crystalline polymer (TLCP) have been investigated by differential scanning calorimetry (DSC). Both, non-isothermal and isothermal crystallizations were carried out. From the non-isothermal experiments, the crystallization temperature was found to be 234°C for a cooling rate of 10°C/min whereas it was only 228°C for 40°C/min for Z 8000B, and was found to be 296°C and 290°C, respectively, for Z 6000. In the isothermal experiment both the thermal and crystallization behaviors were studied as a function of the annealing temperature and annealing time. Two types of transition processes were evidence in the low temperature region of the isothermal crystallization. One is fast transition, which may be regarded as liquid crystal transition, and is characterized by the enthalpy, which is independent of annealing time. The other is slow process, related to crystal perfection, and it shows increases in the transition temperature and enthalpy, which is dependent on annealing time. [source] Crystallization and melting behavior of multi-walled carbon nanotube-reinforced nylon-6 compositesPOLYMER INTERNATIONAL, Issue 1 2006In Yee Phang Abstract The crystallization and melting behavior of neat nylon-6 (PA6) and multi-walled carbon nanotubes (MWNTs)/PA6 composites prepared by simple melt-compounding was comparatively studied. Differential scanning calorimetry (DSC) results show two crystallization exotherms (TCC, 1 and TCC, 2) for PA6/MWNTs composites instead of a single exotherm (TCC, 1) for the neat matrix. The formation of the higher-temperature exotherm TCC, 2 is closely related to the addition of MWNTs. X-ray diffraction (XRD) results indicate that only the ,-phase crystalline structure is formed upon incorporating MWNTs into PA6 matrix, independently of the cooling rate and annealing conditions. These observations are significantly different from those for PA6 matrix, where the increase in cooling rate or decrease in annealing temperature results in the crystal transformation from ,-phase to ,-phase. The crystallization behavior of PA6/MWNTs composites is also significantly different from those reported in PA6/nanoclay systems, probably due to the difference in nanofiller geometry between one-dimensional MWNTs and two-dimensional nanoclay platelets. The nucleation sites provided by carbon nanotubes seem to be favorable to the formation of thermodynamically stable ,-phase crystals of PA6. The dominant ,-phase crystals in PA6/MWNTs composites may play an important role in the remarkable enhancement of mechanical properties. Copyright © 2005 Society of Chemical Industry [source] Heating-induced conformational change of a novel ,-(1,3)- D -glucan from Pleurotus geestanusBIOPOLYMERS, Issue 2 2010Mei Zhang Abstract Recently, we isolated and purified a neutral polysaccharide (PGN) from edible fungus Pleurotus geestanus. Its structure was characterized by a range of physical,chemical methods, including high performance anion exchange chromatography, uronic acid, and protein analyses, size exclusion chromatography with ultraviolet, refractive index and light scattering detectors, and nuclear magnetic resonance. Our results revealed that PGN is a novel ,-(1,3)- D -glucan with glucose attached to every other sugar residues at Position 6 in the backbone. It has a degree of branching of 1/2. Such structure is different from typical ,-(1,3)- D -glucans schizophyllan and lentinan in which DB is 1/3 and 2/5, respectively. Rheological study showed a very interesting melting behavior of PGN in water solution: heating PGN in water leads to two transitions, in the range of 8,12.5°C and 25,60°C, respectively. The melting behavior and conformational changes were characterized by rheometry, micro-differential scan calorimetry, atomic force microscopy, static and dynamic light scattering at different temperatures. The first heating-induced transition corresponds to the disintegration of polymer bundles into small helical clusters, resembling the heating-induced dissociation of SPG in water at 7°C; the second one might correspond to the dissociation of helical strands to individual chains. The ability of PGN to undergo a conformation/viscosity transition in water upon heating is very valuable to immobilize cells or enzymes or therapeutic DNA/RNA, which makes PGN a potentially useful biomaterial. © 2009 Wiley Periodicals, Inc. Biopolymers 93: 121,131, 2010. This article was originally published online as an accepted preprint. The "Published Online" date corresponds to the preprint version. You can request a copy of the preprint by emailing the Biopolymers editorial office at biopolymers@wiley.com [source] Isothermal crystallization kinetics and melting behaviors of nanocomposites of poly(trimethylene terephthalate) filled with nano-CaCO3JOURNAL OF APPLIED POLYMER SCIENCE, Issue 3 2007Mingtao Run Abstract The isothermal crystallization and subsequent melting behavior of poly(trimethylene terephthalate) (PTT) composites filled with nano-CaCO3 were investigated at designated temperatures with differential scanning calorimetry. The Avrami equation was used to fit the isothermal crystallization. The Avrami exponents were determined to be 2,3 for the neat PTT and PTT/CaCO3 composites. The particles of nano-CaCO3, acting as nucleating agents in the composites, accelerated the crystallization rate, with the half-time of crystallization decreasing or the growth rate constant (involving both nucleation and growth rate parameters) increasing. The crystallization activation energy calculated from the Arrhenius formula was reduced as the nano-CaCO3 content increased from 0 to 2%, and this suggested that nano-CaCO3 made the molecular chains of PTT easier to crystallize during the isothermal crystallization process. Subsequent melting scans of the isothermally crystallized composites exhibited triple or double melting endotherms: the greater the content was of nano-CaCO3, the lower the temperature was of the melting peak. The degree of crystallization deduced from the melt enthalpy of composites with the proper concentration of nano-CaCO3 was higher than that of pure PTT, but it was lower when the nano-CaCO3 concentration was more than 2%. The transmission electron microscopy pictures suggested that the dispersion state of nano-CaCO3 particles in the polymer matrix was even when its concentration was no more than 2%, whereas some agglomeration occurred when its concentration was 4%. Polarized microscopy pictures showed that much smaller or less perfect crystals formed in the composites because of the interaction between the molecular chains and nano-CaCO3 particles. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2007 [source] Studies of the intermolecular DNA triplexes of C+·GC and T·AT triplets by electrospray ionization Fourier-transform ion cyclotron resonance mass spectrometryJOURNAL OF MASS SPECTROMETRY (INCORP BIOLOGICAL MASS SPECTROMETRY), Issue 2 2008Cuihong Wan Abstract Formation and stabilities of four 14-mer intermolecular DNA triplexes, consisting of third strands with repeating sequence CTCT, CCTT, CTT, or TTT, were studied by electrospray ionization Fourier-transform ion cyclotron resonance mass spectrometry (ESI-FTICR-MS) in the gas phase. The gas-phase stabilities of the triplexes were compared with their CD spectra and melting behaviors in solution, and parallel correlation between two phases were obtained. In the presence of 20 mM NH4+ (pH 5.5), the formation of the TTT triplex was not detected in both solution and the gas phase. Other triplexes showed the same order, CTCT > CCTT > CTT, of ion abundances in mass spectra and Tm values in solution. The more stable triplexes are those that contained higher percentage of C+·GC triplets and an alternating CT sequence. However, the CCTT with the same C+·GC triplets as the CTCT showed a higher stability than the latter during the gas-phase dissociation. Furthermore, a biphasic triplex-to-duplex-to-single transition was detected in the gas phase, while a monophasic triplex-to-single dissociation was observed in solution. The present results reveal that hydrogen bonds and electrostatic interactions dominate in the gas phase, while base stacking and hydrophobic interactions dominate in solution to stabilize the triplexes. Moreover, weak acidic conditions (pH 5,6) promote the formation of the parallel triplexes. Copyright © 2007 John Wiley & Sons, Ltd. [source] Synthesis of Novel Biomimetic Zwitterionic Phosphorylcholine-Bound Chitosan DerivativeMACROMOLECULAR RAPID COMMUNICATIONS, Issue 7 2006Rong Zeng Abstract Summary: Water-soluble biomimetic chitosan derivative conjugating zwitterionic phosphorylcholine was efficiently prepared through Atherton-Todd reaction under the mild conditions, and the possible formation mechanism of zwitterionic product was related to the nucleophilic attack of adjacent 3-hydroxyl on the D -glucosamine residue to phosphorus with the help of base. UV absorption and melting behaviors of DNA/phosphorylcholine-bound chitosan derivative showed that the phosphorylcholine-bound chitosan derivative could be a new carrier for long-circulating macromolecular drug delivery. Structure of zwitterionic PC-chitosan. [source] | ||||||||||||||||