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Polycondensation
Kinds of Polycondensation Terms modified by Polycondensation Selected AbstractsElectrochemically-Induced Deposition of Amine-Functionalized Silica Films on Gold Electrodes and Application to Cu(II) Detection in (Hydro)Alcoholic MediumELECTROANALYSIS, Issue 19 2005Alain Walcarius Abstract Well-adherent amine-functionalized porous silica films have been deposited on gold electrodes by combining the self-assembly technology, the sol,gel process, and the electrochemical modulation of pH at the electrode/solution interface. A partial self-assembled monolayer of mercaptopropyl-trimethoxysilane (MPTMS) was first formed on disposable gold electrodes from recordable CDs (Au-CDtrodes). The so pretreated MPTMS-Au-CDtrodes were immersed in a stable sol solution (pH,3) containing (3-aminopropyl)-triethoxysilane (APTES) and tetraethoxysilane (TEOS). Polycondensation of the APTES and TEOS precursors was then achieved by applying a negative potential for a given period of time to generate a local pH increase at the electrode/solution interface and promote the deposition of the amine functionalized silica film adhering well to the electrode surface owing to the MPTMS monolayer acting somewhat as a "molecular glue". Various parameters affecting the electrodeposition process have been studied and the film permeability to redox probes in solution was characterized by cyclic voltammetry. The amine-functionalized silica film electrodes were then applied to the preconcentration of copper(II) species prior to their electrochemical detection by anodic stripping differential pulse voltammetry. Getting high sensitivity has however required the application of an electrochemical pre-activation step as the majority of the organo-functional groups were in the form of ammonium moieties (because the film was prepared from an acidic sol). This was achieved by applying a sufficiently negative potential to the electrode surface to reduce protons and increase consequently the amine-to-ammonium ratio within the film and, thus, the efficiency of the precocentration process. The resulting device was then optimized for copper(II) determination in hydroalcoholic medium, giving rise to a linear response in the 0.1,10,,M concentration range. [source] Tuning and Transcription of the Supramolecular Organization of a Fluorescent Silsesquioxane Precursor into Silica-Based Materials through Direct Photochemical Hydrolysis,Polycondensation and MicropatterningADVANCED FUNCTIONAL MATERIALS, Issue 3 2009Xavier Sallenave Abstract A new fluorescent silsequioxane precursor with tuned optical properties and controlled aggregation properties is designed. The two cyclohexyl moieties introduced in the molecular structure allow the formation of very good quality films. The J-aggregated structure is transcribed into the solid by photoacid-catalyzed hydrolysis,polycondensation. Aggregation of the chromophores is reduced and highly fluorescent materials are obtained. The photoacid generator lies on the surface of the homogeneous layer of the sol,gel precursor. This phase separation presents several advantages, including UV protection of the chromophore and easy removal of the PAG. The first example of chemical amplification in the photolithography of the conjugated silsesquioxane precursor is demonstrated. As hydrolysis,polycondensation could be achieved in a controlled way by UV exposure, chemically amplified photolithography is achieved by irradiating a composite film (,110,nm thick) on silicon wafer by using a copper TEM grid as shadow mask. The pattern is produced uniformly on a miscroscopic scale of 3,mm, the photopatterned pixels remaining highly fluorescent. The sizes of the photolithographed pixels correspond to the sizes of the rectangular holes of the 300,×,75 mesh grid (hole: 63,<$>,<$>m,×,204,<$>,<$>m). [source] Amphiphilic Homochiral Oligopeptides Generated via Phase Separation of Nonracemic , -Amino Acid Derivatives and Lattice-Controlled Polycondensation in a Phospholipid EnvironmentHELVETICA CHIMICA ACTA, Issue 11 2003Irina Rubinstein Racemic S -ethyl thioesters of N, -stearoyllysine (=,S -ethyl (R,S)-2-amino-6-(stearoylamino)hexanethioate) and S -ethyl thioesters of , -stearyl glutamic acid (=stearyl (R,S)-4-amino-5-(ethylsulfanyl)-5-oxopentanoate) self-assemble as separated two-dimensional crystalline monolayers within an achiral phospholipid environment of racemic 1,2-dipalmitoylglycerol (DPG) and 1,2-dipalmitoylglycero-3-phosphoethanolamine (DPPE), as demonstrated by grazing-incidence X-ray-diffraction (GIXD) measurements performed on the surface of H2O. Lattice-controlled polycondensation within these crystallites with deuterium-enantiolabeled monomers was initiated by injecting aqueous solutions of Ag+ or I2/KI beneath the monolayers, which yielded mixtures of diastereoisomeric oligopeptides containing up to six to eight repeating units, as analyzed by MALDI-TOF mass spectrometry. Analysis of the diastereoisomeric distribution showed an enhanced relative abundance of the oligopeptides with homochiral sequences containing three or more repeating units. Within the DPPE monolayers, the nucleophilic amino group of the phospholipid operates as an initiator of polymerization at the periphery of the monomer two-dimensional crystallites. Enhanced relative abundance of enantiomerically enriched homochiral oligopeptides was obtained by the polycondensation of nonracemic monomers. This enhancement indicated a phase separation into racemic and enantiomorphous monomer crystallites within the phospholipid environment, although this separation could not be observed directly by GIXD. A possible role that might have been played by crystalline assemblies for the abiotic generation and amplification of oligopeptides with homochiral sequences is discussed. [source] Benzoxazine containing polyester thermosets with improved adhesion and flexibilityJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 19 2010Alev Tuzun Abstract High molecular weight polyesters containing thermally curable benzoxazine units in the main chain have been synthesized. For this purpose, first the diol functional monomer is synthesized through the Mannich and subsequent ring closure reactions of bisphenol-A, paraformaldehyde, and 5-amino-1-pentanol. Polycondensation of the resulting benzoxazine and pyromellitic dianhydride or 4-4,-(hexafluoroisopropylidene) diphatalic anhydride with or without dibutyltin laurate yielded the corresponding polyesters with the molecular weights between 5800 and 7000 Da. The structures of the precursor diol monomer and the resulting polyesters are confirmed by Fourier transform infrared spectroscopy and proton nuclear magnetic resonance spectroscopy analysis. Curing behavior of both the monomer and polymers has also been studied by differential scanning calorimetry. Flexible films of the polyesters were obtained by solvent casting on tin plates and crosslinked by heating in the absence of any catalyst. The cured films exhibited high flexibility and adhesion on the tin plates as determined by ASTM and DIN tests. Thermal properties of the cured polymers were also investigated by thermogravimetric analysis (TGA). © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 4279,4284, 2010 [source] Kinetics and Modeling of Melt Polycondensation for Synthesis of Poly[(butylene succinate)- co -(butylene terephthalate)], 1 , EsterificationMACROMOLECULAR REACTION ENGINEERING, Issue 9-10 2010Lixia Hu Abstract The kinetics of the tetrabutyl titanate-catalyzed homogeneous succinic acid/1,4-butylenediol (BDO) and heterogeneous terephthalic acid/BDO esterifications were investigated experimentally and theoretically. A unified kinetic model considering two main esterifications as well as one reversible polycondensation and two THF-forming side reactions has been developed for the two esterification systems. The model agrees well with the experimental results. The effects of reaction temperature, diol/diacid ratio, catalyst amount, and heterogeneity on the esterification kinetics are simulated and discussed. [source] Polycondensation of lactic acid catalyzed by organic acid anhydridesPOLYMER INTERNATIONAL, Issue 10 2007Yanbin Bai Abstract Poly(lactic acid) was prepared by the utilization of the acid anhydrides cis -butenedoic anhydride, phthalic anhydride and pyromellitic dianhydride as catalysts. The effect of the amount of catalyst, temperature and reaction time on the polymerization was investigated in detail. The results show that the acid anhydride catalysts are very efficient in bulk polycondensation, giving poly(D,L -lactic acid) with average molecular weights (Mw) of (1.7,2.3) × 104 in high yield. Copyright © 2007 Society of Chemical Industry [source] Inorganic Precipitated Silica Gel.CHEMICAL ENGINEERING & TECHNOLOGY (CET), Issue 6 2010Gel Properties, Part 1: Gelation Kinetics Abstract Precipitated silica (SiO2) is industrially produced by mixing a silicate solution with acid in a semi-batch process. Polycondensation of monomeric silica leads to the formation of particles which aggregate and eventually form a particulate gel. However, this is instantly fragmented by the mechanical energy input caused by the stirrer. Shrinkage and compaction of these fragments lead to the final product aggregates. It is the aim of this study to enable tailoring of the structure and size of these product particles via the process parameters. The present paper describes the influence of the parameters temperature, ionic strength, and composition, which affect the pH, on the properties of unstirred gels regarding their elasticity and thus their fragmentation behavior. Gelation time may be qualitatively estimated solely from the concentration of the feed materials. [source] Homogeneous Two-Component Polycondensation Without Strict Stoichiometric Balance via the Tsuji,Trost Reaction: Remote Control of Two Reaction Sites by Catalysis.CHEMINFORM, Issue 33 2004Nobuyoshi Nomura No abstract is available for this article. [source] Highly Emissive and Electrochemically Stable Thienylene Vinylene Oligomers and Copolymers: An Unusual Effect of Alkylsulfanyl SubstituentsADVANCED FUNCTIONAL MATERIALS, Issue 10 2010Shehzad Jeeva Abstract The synthesis, unexpected efficient photoluminescence, and reversible electrochemical p- and n-doping of new conjugated thienylene vinylene materials functionalized with alkylsulfanyl substituents poly(trithienylene vinylene) (PTTV) and poly(dithienylvinyl- co -benzothiadiazole) (PDTVB) along with dithienylvinylene-based oligomers is reported. The materials are studied by thermal and X-ray diffraction analysis, optical spectroscopy, cyclic voltammetry, and spectroelectrochemistry. Organic field-effect transistors (OFETs) are fabricated with PTTV and PDTVB. The polymers, prepared by Stille polycondensation, exhibit good thermal stability and a photoluminescent quantum yield in the range 34%,68%. Low bandgaps (1.5,1.8,eV), estimated by optical and electrochemical measurements along with high stability of both redox states, suggest that these structures are promising materials for photovoltaic applications. OFETs fabricated with PDTVB reveal a hole mobility of 7,×,10,3,cm2 V,1 s,1 with on/off ratio 105, which are comparatively high values for completely amorphous polymer semiconductors. [source] Red-Emitting Polyfluorenes Grafted with Quinoline-Based Iridium Complex: "Simple Polymeric Chain, Unexpected High Efficiency"ADVANCED FUNCTIONAL MATERIALS, Issue 1 2010Zhihua Ma Abstract A series of red-light emitting electrophosphorescent polyfluorenes (PFs) with varying content of a quinoline-based iridium complex, (PPQ)2Ir(acac) (bis(2,4-diphenylquinolyl-N,C2,) iridium(acetylacetonate)), in the side chain are synthesized by Suzuki polycondensation. Because of the efficient Förster energy transfer from the PF main chain to (PPQ)2Ir(acac) and direct charge trapping on the complex, the electroluminescent emission from PF is nearly completely quenched, even though the amount of iridium complex incorporated into the polymers is as low as 1,mol %. Based on a single-layer device configuration, a luminous efficiency of up to 5.0,cd A,1 with a luminance of 2000,cd m,2 and Commission Internationale de L'Eclairage coordinates of (0.63, 0.35) (x, y) is realized, which is far superior to that of previously reported red-light emitting PFs containing benzothiazole- and isoquinoline-based iridium complexes. This result is beyond expectations, especially when considering that the simple polymeric chain involved has no additional charge-transporting moieties. Noticeably, the device efficiency remains as high as 4.2,cd A,1 with a luminance of 4000,cd m,2 even at current densities of 100,mA cm,2. Further optimization of the device configuration by incorporating an additional electron-injection layer leads to improved efficiencies of 8.3 and 7.5,cd A,1 at luminances of 100 and 1000,cd m,2, respectively. This state-of-the-art performance indicates that covalently attaching quinoline-based iridium complexes to a PF backbone is a simple and effective strategy to develop high-efficiency red-light emitting electrophosphorescent polymers. [source] Tuning and Transcription of the Supramolecular Organization of a Fluorescent Silsesquioxane Precursor into Silica-Based Materials through Direct Photochemical Hydrolysis,Polycondensation and MicropatterningADVANCED FUNCTIONAL MATERIALS, Issue 3 2009Xavier Sallenave Abstract A new fluorescent silsequioxane precursor with tuned optical properties and controlled aggregation properties is designed. The two cyclohexyl moieties introduced in the molecular structure allow the formation of very good quality films. The J-aggregated structure is transcribed into the solid by photoacid-catalyzed hydrolysis,polycondensation. Aggregation of the chromophores is reduced and highly fluorescent materials are obtained. The photoacid generator lies on the surface of the homogeneous layer of the sol,gel precursor. This phase separation presents several advantages, including UV protection of the chromophore and easy removal of the PAG. The first example of chemical amplification in the photolithography of the conjugated silsesquioxane precursor is demonstrated. As hydrolysis,polycondensation could be achieved in a controlled way by UV exposure, chemically amplified photolithography is achieved by irradiating a composite film (,110,nm thick) on silicon wafer by using a copper TEM grid as shadow mask. The pattern is produced uniformly on a miscroscopic scale of 3,mm, the photopatterned pixels remaining highly fluorescent. The sizes of the photolithographed pixels correspond to the sizes of the rectangular holes of the 300,×,75 mesh grid (hole: 63,<$>,<$>m,×,204,<$>,<$>m). [source] Highly Fluorescent Mesostructured Films that consist of Oligo(phenylenevinylene),Silica Hybrid Frameworks,ADVANCED FUNCTIONAL MATERIALS, Issue 22 2008Norihiro Mizoshita Abstract Highly fluorescent and visible-light-responsive mesostructured organosilica films are successfully obtained by acidic sol,gel polycondensation of oligo(phenylenevinylene) (OPV)-bridged organosilane and tetraethoxysilane precursors in the presence of a template surfactant. The OPV-bridged organosilane precursors with different lateral alkoxy substituents, hexyloxy and 2-ethylhexyloxy, and no substituent, are synthesized by Rh-catalyzed silylation of corresponding aromatic iodides. From the organosilane precursors, three kinds of mesostructured OPV,silica hybrid films are prepared by spin-casting using evaporation-induced self-assembly. UV-vis absorption and fluorescence behavior of the OPV,silica hybrid films show that the optical properties and intermolecular interactions of the OPV moieties embedded within the organosilica frameworks strongly depend on the lateral alkoxy substituents in the precursors. The hexyloxy and 2-ethylhexyloxy substituents prevent aggregation of the OPV units in the organosilica frameworks; this result leads to high fluorescence quantum yields of 0.48,0.61 and 0.63,0.66, respectively, while non-substitution leads to lower fluorescence quantum yields of 0.25,0.34. Fluorescence decay profiles of the organosilica hybrid films also confirm a suppression of the aggregation of OPV moieties by the lateral substituents. These mesostructured organosilica films with significant optical properties in the visible-light region are promising as a new class of phosphor materials. [source] Reversible Cluster Formation of Colloidal Nanospheres by Interparticle Photodimerization,ADVANCED FUNCTIONAL MATERIALS, Issue 5 2004X. Yuan Abstract Crosslinked spherical nanoparticles based on trimethoxysilane monomers have been prepared by polycondensation in aqueous emulsion. These particles have been labeled chemically at their surface region with two different types of organic dye molecules (cinnamate, coumarin), which both are well known for their ability to undergo a reversible photodimerization if irradiated with light of a suitable wavelength. Upon irradiation of dilute solutions of these nanoparticles with UV light, the photodimerization of labels belonging to different colloidal nanoparticles caused the formation of large colloidal clusters consisting of chemically bound individual nanospheres. This process has been quantitatively investigated using light scattering and atomic force microscopy. Importantly, utilizing the reversibility of the photoreaction, the clusters could be broken up by irradiation of the sample with UV light of shorter wavelengths than the light used for their formation [source] Synthesis of Components for the Generation of Constitutional Dynamic Analogues of Nucleic AcidsHELVETICA CHIMICA ACTA, Issue 1 2008David Abstract The introduction of dynamic covalent polymers, in which the monomer units are linked by reversible covalent bonds and can undergo component exchange, opens up new possibilities for the generation of functional materials. Extending this approach to the generation of dynamic biopolymers in aqueous media, which are able to adapt constitution (sequence, length) to external factors (e.g., environment, medium, template), would provide an alternative approach to the de novo design of functional dynamic bio-macromolecules. As a first step towards this goal, various mono- and bifunctionalised (hetero- and homotopic) nucleic acid-derived building blocks of type I,X have been synthesised for the generation of dynamic main-chain and side-chain reversible nucleic acid analogues. Hydrazide- and/or acetal (protected carbonyl)-functionalised components were selected, which differ in terms of flexibility, length, net formal charge, and hydrazide/acetal substituents, in order to explore how such factors may affect the properties (structure, solubility, molecular recognition features) of the polymer products that may be generated by polycondensation. [source] Amphiphilic Homochiral Oligopeptides Generated via Phase Separation of Nonracemic , -Amino Acid Derivatives and Lattice-Controlled Polycondensation in a Phospholipid EnvironmentHELVETICA CHIMICA ACTA, Issue 11 2003Irina Rubinstein Racemic S -ethyl thioesters of N, -stearoyllysine (=,S -ethyl (R,S)-2-amino-6-(stearoylamino)hexanethioate) and S -ethyl thioesters of , -stearyl glutamic acid (=stearyl (R,S)-4-amino-5-(ethylsulfanyl)-5-oxopentanoate) self-assemble as separated two-dimensional crystalline monolayers within an achiral phospholipid environment of racemic 1,2-dipalmitoylglycerol (DPG) and 1,2-dipalmitoylglycero-3-phosphoethanolamine (DPPE), as demonstrated by grazing-incidence X-ray-diffraction (GIXD) measurements performed on the surface of H2O. Lattice-controlled polycondensation within these crystallites with deuterium-enantiolabeled monomers was initiated by injecting aqueous solutions of Ag+ or I2/KI beneath the monolayers, which yielded mixtures of diastereoisomeric oligopeptides containing up to six to eight repeating units, as analyzed by MALDI-TOF mass spectrometry. Analysis of the diastereoisomeric distribution showed an enhanced relative abundance of the oligopeptides with homochiral sequences containing three or more repeating units. Within the DPPE monolayers, the nucleophilic amino group of the phospholipid operates as an initiator of polymerization at the periphery of the monomer two-dimensional crystallites. Enhanced relative abundance of enantiomerically enriched homochiral oligopeptides was obtained by the polycondensation of nonracemic monomers. This enhancement indicated a phase separation into racemic and enantiomorphous monomer crystallites within the phospholipid environment, although this separation could not be observed directly by GIXD. A possible role that might have been played by crystalline assemblies for the abiotic generation and amplification of oligopeptides with homochiral sequences is discussed. [source] Cover Picture: Functionalized Gold Nanoparticles Mimic Catalytic Activity of a Polysiloxane-Synthesizing Enzyme (Adv. Mater.ADVANCED MATERIALS, Issue 10 200510/2005) Abstract A system that acts as a biomimetic of the silica-synthesizing enzyme found in a marine sponge is reported by Morse and co-workers on p.,1234. Gold nanoparticles (GNPs) are functionalized with the same organic moieties that are found in the enzyme's catalytic site. Interaction between the nucleophilic (OH-terminated) and hydrogen-bonding (imidazole-terminated) GNPs, as shown on the cover, is required for the hydrolysis of a silicon alkoxide precursor and subsequent polycondensation to form silica at a low temperature and near-neutral pH. Replacement of either of the required functional groups by a non-reactive methyl group abolishes catalysis in this synthetic system, as it does in the biological enzyme. Cover art provided by Peter Allen. [source] Highly Stereoselective Synthesis of Arylene-Silylene-Vinylene PolymersADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 9 2005Mariusz Majchrzak Abstract Stereoregular trans -arylene-silylene-vinylene polymers of Mw=13100,34800 and PDI=1.6,2.9 of the general formulas CH2CH[SiMe2C6H4 -SiMe2CHCH](16, 17, 18) and CH2CH[(R)CHCHC6H4CHCH](where R=Me2Si- pC6H4 - SiMe2, Me2Si- mC6H4SiMe2 and Me2SiC6H4C6H4SiMe2) (19, 20, 21) have been effectively synthesized via silylative coupling (SC) homopolycondensation of bis(vinyldimethylsilyl)arenes (10, 12, 14) and cross-polycondensation of 4-(vinyldimethylsilyl)styrene (11) as well as cross-copolycondensation of bis(vinyldimethylsilyl)arenes (10, 12 and 14) with 1,4-divinylbenzene (9) catalyzed by [RuH(Cl)(CO)(PCy3)2] (7). Such highly stereoregular products cannot be synthesized via ADMET polycondensation or ring opening metathesis ROM or polyaddition of hydridosilanes to acetylenes. [source] Synthesis and characterization of new soluble polyamides from an unsymmetrical diamine bearing a bulky triaryl pyridine pendent groupJOURNAL OF APPLIED POLYMER SCIENCE, Issue 6 2010Mousa Ghaemy Abstract New unsymmetrical diamine monomer containing triaryl pyridine pendent group, 2,4-diaminophenyl [4-(2, 6-diphenyl-4-pyridyl) phenyl]ether, was synthesized via aromatic substitution reaction of 1-chloro-2,4-dinitrobenzene with 4-(2,6-diphenyl-4-pyridyl) phenol, followed by Pd/C-catalyzed hydrazine reduction. Five Polyamides (PA) were prepared by the phosphorylation polycondensation of different dicarboxylic diacids with the diamine. Inherent viscosities of PAs were in the range 0.51,0.59 g/dL indicating formation of medium molecular weight polymers. The weight and number average molecular weights of a PA, (PA-d), determined by GPC were 6944 g/mol and 17,369 g/mol, respectively. PAs exhibited glass-transition temperatures (Tg) in the range 140,235°C. These polymers, essentially amorphous, were soluble in polar aprotic solvents such as DMF, NMP, DMAc, DMSO, pyridine, m -cresol, and THF. The initial decomposition temperatures (Ti) of PAs, determined by TGA in air, were in the range 300,380°C indicating their good thermal stability. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010 [source] Synthesis and characterization of imine-coupled polyphenols containing carbazole unitsJOURNAL OF APPLIED POLYMER SCIENCE, Issue 3 2009smet Kaya Abstract Imine coupled phenolic monomers containing carbazole unit were synthesized in four steps. The monomers were polymerized via oxidative polycondensation by air as oxidant in an aqueous alkaline medium at 50°C. The structures of compounds were confirmed by ultraviolet,visible (UV,vis), Fourier transform infrared, and 1H- and 13C-NMR techniques. The conductivity measurements of these polymers were made by the four-point probe technique and iodine was used as doping agent. The highest occupied molecular orbital, the lowest unoccupied molecular orbital, and electrochemical and optical band gap values were calculated by the results of the UV,vis and the cyclic voltammetry measurement, respectively. The number-average molecular weight, weight-average molecular weight, and polydispersity index values were determined by the size exclusion chromatography technique. Also, thermal behavior of these polymers was determined by thermogravimetric/differential thermal analysis measurements in a N2 atmosphere between 20 and 1000°C. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009 [source] Synthesis and magnetic properties of novel fully conjugated polymeric complexes containing 1,10-phenanthrolineJOURNAL OF APPLIED POLYMER SCIENCE, Issue 4 2008Renhua Zheng Abstract A novel fully conjugated polymer containing 1,10-phenanthroline (DAPcDOD) was first synthesized by the polycondensation of 2,7-dimethyl-2,4,6-octatriene-1,8-dial with 5,6-diamine-1,10-phenanthroline. Three polymeric complexes were first prepared by the reaction of DAPcDOD with NiSO4, CoCl2, and FeSO4, respectively. The structures of the polymer and the complexes were characterized by IR, 1H-NMR, and elemental analysis. The magnetic behaviors of these complexes were measured as a function of magnetic field strength (0,50 kOe) at 5 K and as a function of temperature (5,300 K) at a magnetic field strength of 30 kOe. The results show that DAPcDOD,Ni2+ and DAPcDOD,Co2+ were soft ferromagnets, whereas DAPcDOD,Fe2+ exhibited the features of an antiferromagnet. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008 [source] Synthesis and properties of homopolyamide and copolyamides fibers based on 2,6-bis(p -aminophenyl)benzo[1,2-d;5,4- d,]bisoxazoleJOURNAL OF APPLIED POLYMER SCIENCE, Issue 3 2008Xiangqun Chen Abstract A novel aromatic homopolyamide with benzobisoxazole units in the main chain was synthesized with 2,6-bis(p -aminophenyl)benzo[1,2- d;5,4- d,]bisoxazole and terephthaloyl chloride by low temperature solution polycondensation, the inherent viscosity of which was 1.98 dL/g. The diamine and p -phenylendiamine with terephthaloyl chloride were used to synthesize the copolyamides. The structures of homopolyamide and copolyamides were characterized by IR spectra, elemental analysis, and wide-angle X-ray diffraction. Wide-angle X-ray diffraction measurements showed that homopolyamide and copolyamides were predominantly crystallinity. The results of thermal analysis indicated that the thermal stabilities of the copolymer increased with an increase of the molar fraction of benzobisoxazole in the copolymers. The thermal stability of the copolyamides with decomposition temperatures (at 10% weight loss) above 570°C was better than that of poly(p -phenylene terephthalamide) (PPTA). Fibers of homopolyamide and copolyterephthalamides were spun from lyotropic liquid crystal dope in 100% H2SO4. When compared with PPTA fibers prepared under the same conditions, the tensile strengths of copolyamides fibers improved by 20,33% with tensile strengths of 1.81 GPa, tensile moduli of 76 GPa, and elongations at break of 3.8,4.1%, which indicated that copolyamides fibers had outstanding mechanical properties. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008 [source] Dehydration of benzene through fluorine containing aromatic polyamide membrane by pervaporationJOURNAL OF APPLIED POLYMER SCIENCE, Issue 1 2008P. K. Gutch Abstract A series of soluble polyamides were synthesized by direct polycondensation of the 5- tert -butyl isophthalic acid with different diamines. Solution (20%) of the polymers in suitable solvents was used to cast the membranes. The membranes showed selectivity toward the benzene (Bz) in a mixture of Bz/water (H2O). Water affinity of the membrane was found to be lower than that of Bz. The polyamide incorporating hexafluoro isopropylidene moiety was promising for the dehydaration of Bz and breaking of Bz/H2O azeotrope. The polymers exhibited inherent viscosities, ranging from 0.40 to 0.92 dL/g and 10% weight loss in synthetic air up to 474°C. Glass transition temperature measured by DSC and DMA reached up to 258°C. The membranes were pale yellow in appearance having tensile strength up to 85 MPa, modulus of elasticity up to 2.6 GPa, and elongation at break up to 9.5%, depending upon the exact repeating unit structure. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008 [source] Synthesis and characterization of amphiphilic biodegradable poly(glutamic acid- co -lactic acid- co -glycolic acid) by direct polycondensationJOURNAL OF APPLIED POLYMER SCIENCE, Issue 6 2008Dedai Lu Abstract Poly(glutamic acid- co -lactic acid- co -glycolic acid) (PGLG), an amphiphilic biodegradable copolymer, was synthesized by simply heating a mixture of L -glutamic acid (Glu), DL -lactic acid, and glycolic acid with the present of stannous chloride. The unique branched architecture comprising of glutarimide unit, polyester unit, and polyamide unit was confirmed by NMR spectrum. The PGLG was soluble in many organic solvents and aqueous solution of sodium hydroxide (pH , 9.0). The thermal properties were evaluated using thermogravimetric analysis and differential scanning calorimetry. Molecular weights were determined by 1H NMR end-group analysis and GPC, respectively, and the results indicated that the higher Glu content resulted in a decrease of the molecular weight. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008 [source] The synthesis of block copolyetherketones based on 4,4,-dichlorodiphenylketone, phenolphthaleine, and bisphenol A and investigation of their propertiesJOURNAL OF APPLIED POLYMER SCIENCE, Issue 4 2008S. Ozden Abstract Block structured polyethers based on phenolphthaleine, 4,4,-dichlorodiphenylketone, and bisphenol A with different degrees condensation (n = 1, 5, 10, and 20) were synthesized by means of acceptor-catalytic polycondensation. Equaimolar quantities of chloranhydrides of iso- and terephthalic acids were used. Higher molecular masses were obtained from longer oligoketones with higher condensation degrees. Better molecular packing, increased thermal and mechanical properties were obtained with higher condensation degrees of oligoketones. © 2007 Wiley Periodicals, Inc. JAppl Polym Sci, 2008 [source] Unexpected fluorescence emission of poly(,,,- L -malic acid) in aqueous mediumJOURNAL OF APPLIED POLYMER SCIENCE, Issue 3 2007Yaofeng Fan Abstract Unexpected fluorescence of poly(,,,- L -malic acid) (,,,-PMA) without traditional fluorophore was observed firstly. This fluorescent polymer was synthesized via melt polycondensation of L -malic acid. The polymer was characterized by gel permeation chromatography (GPC), nuclear magnetic resonance (NMR), differential scanning calorimetry (DSC), thermogravimetry (TG), Fourier transform infrared spectroscopy (IR), Fourier transform Raman spectroscopy (Raman), and X-ray powder diffractometry (XRD). The high molecular weight ,,,-PMA was synthesized by the optimum polycondensation at 130°C for 15 h, followed by fractional precipitation with diethyl ether and petroleum ether. The degree of branching of ,,,-PMA was from 10% to 20% according to the reaction condition. Terminal group of ,,,-PMA was mainly hydroxycarboxylic group companied with a few CHCHCOOH groups owing to dehydration of a normal terminal during the melt polycondensation. A fluorescence emission maximum of ,,,-PMA in water appeared at 420 nm when it was excited at 340 nm. Further study indicated that the fluorescence intensity was concentration-dependent, pH-dependent, and molecular-weight-dependent. The fluorescence formation may result from multichain aggregations, which was formed readily in aqueous solution due to intermolecular hydrogen bonds between branched ,,,-PMA. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2007 [source] CHANGES IN MAJOR ANTIOXIDANT COMPOUNDS DURING AGING OF TRADITIONAL BALSAMIC VINEGARJOURNAL OF FOOD BIOCHEMISTRY, Issue 1 2010ELENA VERZELLONI ABSTRACT Traditional balsamic vinegar (TBV) shows antioxidant capacity that increases passing from cask 5, containing the youngest vinegar, to cask 1 containing the oldest vinegar. This increase in antioxidant capacity is a consequence of both the concentration of compounds already present and of new antioxidants formation and is positively related to the increase in the polyphenolic content and in the Maillard reaction/caramellization products. During TBV aging, some reactions involving flavonoids and tannins take place. Tannins can undergo acid-catalyzed cleavage of their interflavonoid bonds with subsequent condensation of other flavonoid molecules. In addition, the low pH, the decrease of the water content and the presence of aldehydes, may promote flavonoids polycondensation. These reactions explain the observed increase in polymeric phenolic compounds and the decrease in monomeric flavonoids. During TBV aging an increase in the browning index is observed as a consequence of the polycondensation reactions of flavonoids and of brown melanoidins accumulation. PRACTICAL APPLICATIONS Traditional balsamic vinegar is a potentially healthy seasoning with high antioxidant capacity that increases during the aging resulting in a product with a strong antioxidant capacity and rich in phenolic compounds such as phenolic acids, monomeric catechins, flavonols and tannins. It also contains other antioxidants such as melanoidins derived from the Maillard and caramelization reaction that occur during must boiling and traditional balsamic vinegar aging. Independently of their bioavailability, traditional balsamic vinegar can contribute to supply antioxidant molecules that play an important role in protecting the gastrointestinal tract itself against peroxidation, thereby limiting the formation of detrimental lipid degradation products. [source] Polyamides nanocapsules: Modeling and wall thickness estimationAICHE JOURNAL, Issue 6 2006K. Bouchemal Abstract This work provides a better understanding for effective control of the nanocapsules wall thickness. Polyamides based nanocapsules are prepared by interfacial polymerization combined with spontaneous emulsification. A clear guideline of how factors such as monomer concentration, diffusion, interfacial reaction, or water swelling influence the capsule formation is very important to the control of capsule wall structure and release performance. In this goal, the macroscopic planar models of the interfacial polycondensation between diethylenetriamine and sebacoyle chloride are studied experimentally and theoretically. This planar model is developed to examine the kinetics of the reaction and to perform the estimation of parameters thanks to the experiment measurements. The effect of the operating conditions on the wall thickness is also studied. The model is shown to be consistent with the experimental data. Next, the spherical model is deduced from the first one. The results obtained with this model are in accordance with some observations of wall thickness. From this model, the increase of the wall thickness is predicted for several operating conditions. © 2006 American Institute of Chemical Engineers AIChE J, 2006 [source] Regioregular poly(3-alkanoylthiophene): Synthesis and electrochemical, photophysical, charge transport, and photovoltaic propertiesJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 21 2010Chao Wang Abstract Head-to-tail regioregular poly(3-heptanoylthiophene) (PHOT) was synthesized by Ni-catalyzed polycondensation of the 2,2-dimethyl-1,3-propanediol-protected Grignard monomer followed by deprotection. Cyclic voltammetric (CV) study demonstrates that the highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) of PHOT are 0.5 eV lower in energy than those of the head-to-tail poly(3-hexylthiophene) (HT-P3HT). Their optical band gaps are essentially the same. Incomplete photoluminescence (PL) quenching was observed in thin films of the 1:1 blend of PHOT and HT-P3HT. PHOT displayed a glass transition at ,269 °C and decomposed at ,300 °C according to differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA). Wide-angle X-ray diffraction (WAXD) study showed that PHOT exists in a not highly ordered state in solid films especially in the ,-stacking direction. Only p -channel activity was observed in field-effect transistors (FETs) for PHOT. The hole mobility was on the order of 10,4 cm2 V,1 s,1. Photovoltaic devices with an active layer of 1:1 blend of PHOT and PC71BM had a power conversion efficiency (PCE) of ,0.5%. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2010 [source] From polymeric particles to multifunctional nanocapsules for biomedical applications using the miniemulsion processJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 3 2010Katharina Landfester Abstract The miniemulsions process represents a versatile tool for the formation of polymeric nanoparticles consisting of different kinds of polymer as obtained by a variety of polymerization types ranging from radical, anionic, cationic, enzymatic polymerization to polyaddition, and polycondensation. The process perfectly allows the encapsulation of hydrophilic and hydrophobic liquids and solids in polymeric shells, molecularly dissolved dyes or other components. In combination with a specific functionalization of the nanoparticles' or nanocapsules' surfaces and the possibility to release substances in a defined way from the interior, complex nanoparticles or nanocapsules are obtained, which are ideally suited for application in biomedical application as marker and targeted drug-delivery system. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 493,515, 2010 [source] Cyclic polymers: Synthetic strategies and physical propertiesJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 2 2010Hans R. Kricheldorf Abstract Syntheses of cyclic polymers including cyclic homopolymers, cyclic block copolymers, sun-shaped polymers, and tadpole polymers are discussed on the basis of a differentiation between synthetic methods and synthetic strategies (e.g., polycondensation, ring,ring equilibration, or ring-expansion polymerization). Furthermore, all synthetic methods are classified as kinetically or thermodynamically controlled reactions. Characteristic properties of cyclic polymers such as smaller hydrodynamic volume, lower melt viscosities, and higher thermostabilities are compared to the properties of their linear counterparts. Furthermore, the nanophase separation of cyclic diblock copolymers is discussed. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 251,284, 2010 [source] | ||||||||||||||||||||||||||||