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Acid Groups (acid + groups)
Kinds of Acid Groups Selected AbstractsPTFE Micropowder Functionalized with Carboxylic Acid GroupsMACROMOLECULAR MATERIALS & ENGINEERING, Issue 6 2008Uwe Lappan Abstract PTFE powder irradiated in air at room temperature was studied by infrared spectroscopy, potentiometric titration with sodium hydroxide, and polyelectrolyte titration with poly(diallyl dimethylammonium chloride). Through the radiation-induced degradation COF groups are formed in the material, which can be hydrolyzed to COOH groups. About 10,20% of the COOH groups are located at the surface of the PTFE particle. The COOH groups start to decompose under oxidizing conditions at temperatures above 200,°C. The decarboxylation results in the formation of CFCF2 groups, which are oxidized to COF groups in the presence of air. [source] Thermodynamic Analysis of Receptors Based on Guanidinium/Boronic Acid Groups for the Complexation of Carboxylates, ,-Hydroxycarboxylates, and Diols: Driving Force for Binding and CooperativityCHEMISTRY - A EUROPEAN JOURNAL, Issue 15 2004Sheryl L. Wiskur Dr. Abstract The thermodynamics of guanidinium and boronic acid interactions with carboxylates, ,-hydroxycarboxylates, and diols were studied by determination of the binding constants of a variety of different guests to four different hosts (7,10). Each host contains a different combination of guanidinium groups and boronic acids. The guests included molecules with carboxylate and/or diol moieties, such as citrate, tartrate, and fructose, among others. The Gibbs free energies of binding were determined by UV/Vis absorption spectroscopy, by use of indicator displacement assays. The receptor based on three guanidinium groups (7) was selective for the tricarboxylate guest. The receptors that incorporated boronic acids (8,10) had higher affinities for guests that included ,-hydroxycarboxylate and catechol moieties over guests containing only carboxylates or alkanediols. Isothermal titration calorimetry revealed the enthalpic and entropic contributions to the Gibbs free energies of binding. The binding of citrate and tartrate was investigated with hosts 7,10, for which all the binding events were exothermic, with positive entropy. Because of the selectivity of hosts 8,10, a simple boronic acid (14) was also investigated and determined to be selective for ,-hydroxycarboxylates and catechols over amino acids and alkanediols. Further, the cooperativity of 8 and 9 in binding tartrate was also investigated, revealing little or no cooperativity with 8, but negative cooperativity with 9. A linear entropy/enthalpy compensation relationship for all the hosts 7,10, 14, and the carboxylate-/diol-containing guests was also obtained. This relationship indicates that increasing enthalpy of binding is offset by similar losses in entropy for molecular recognition involving guanidinium and boronic acid groups. [source] Improved Detection Limit and Stability of Amperometric Carbon Nanotube-Based Immunosensors by Crosslinking Antibodies with PolylysineELECTROANALYSIS, Issue 2 2008Vito Cataldo Abstract Amperometric immunosensor configurations featuring covalently bound anti-biotin antibodies (Ab) embedded into a polylysine (PLL)-single walled carbon nanotube (SWCNT) composite layer were evaluated. Assemblies were made by first oxidizing pyrolytic graphite (PG) electrodes to form surface carboxylic acid groups, to which PLL, SWCNTs and anti-biotin were covalently linked. Incorporating SWCNT into PLL-antibody assemblies improved the amperometric detection limit for biotin (Ag) labeled with horseradish peroxidase to 10,fmol mL,1. Anti-biotin embedded into the PLL matrix had improved thermal stability and retained its binding ability for biotin after exposure to temperatures of 42,°C for up to 3 hours, while the noncrosslinked antibody was inactivated at this temperature in several minutes. [source] Xanthine Sensors Based on Anodic and Cathodic Detection of Enzymatically Generated Hydrogen PeroxideELECTROANALYSIS, Issue 6 2007Aminur Rahman Abstract A xanthine biosensor was fabricated by the covalent immobilization of xanthine oxidase (XO) onto a functionalized conducting polymer (Poly-5, 2,: 5,, 2,-terthiophine-3-carboxylic acid), poly-TTCA through the formation of amide bond between carboxylic acid groups of poly-TTCA and amine groups of enzyme. The immobilization of XO onto the conducting polymer (XO/poly-TTCA) was characterized using cyclic voltammetry, quartz crystal microbalance (QCM), and X-ray photoelectron spectroscopy (XPS) techniques. The direct electron transfer of the immobilized XO at poly-TTCA was found to be quasireversible and the electron transfer rate constant was determined to be 0.73,s,1. The biosensor efficiently detected xanthine through oxidation at +0.35,V and reduction at ,0.25,V (versus Ag/AgCl) of enzymatically generated hydrogen peroxide. Various experimental parameters, such as pH, temperature, and applied potential were optimized. The linear dynamic ranges of anodic and cathodic detections of xanthine were between 5.0×10,6,1.0×10,4 M and 5.0×10,7 to 1.0×10,4,M, respectively. The detection limits were determined to be of 1.0×10,6,M and 9.0×10,8,M with anodic and cathodic processes, respectively. The applicability of the biosensor was tested by detecting xanthine in blood serum and urine real samples. [source] Study of Factors Affecting the Performance of Voltammetric Copper Sensors Based on Gly-Gly-His Modified Glassy Carbon and Gold ElectrodesELECTROANALYSIS, Issue 12 2006Guozhen Liu Abstract This paper reports a study of the factors affecting the analytical performance of gold and glassy carbon electrodes modified with the tripeptide Gly-Gly-His for the detection of copper ions. Gly-Gly-His is attached to a glassy carbon (GC) surface modified with 4-carboxyphenyl moieties or a gold surface modified with 3-mercaptopropionic acid by the reaction of the N-terminal amine group of the peptide with the carboxylic acid groups of the monolayer via carbodiimide activation. X-ray photoelectron spectroscopy was used to characterize the steps in the biosensor fabrication. It was found that the analytical performance of a sensor prepared with Gly-Gly-His on a GC electrode was similar to that on a gold electrode under the same conditions. The performance was greatly enhanced at higher temperature, no added salt during copper accumulation and longer accumulation time within a pH range of 7,9. Interference studies and investigations of stability of the Gly-Gly-His sensor are reported. Analysis of natural water samples show that the sensors measure only copper ions that can complex at the sensor surface. Strongly complexed copper in natural water is not measured. Despite greater stability of diazonium salt derived monolayers on carbon surfaces compared with alkanethiols self-assembled monolayers on gold, the stability of the sensors was essentially the same regardless of the modification procedure. [source] The Effects of Ascorbic Acid on Penicillin-induced Epileptiform Activity in RatsEPILEPSIA, Issue 7 2007Mustafa Ayyildiz Summary:,Purpose: Epileptic seizure results from excessive discharge in a population of hyperexcitable neurons. A number of studies help to document the effects of active oxygen free radical scavengers such as ,-tocopherol or ascorbic acid (vitamin C). In the present study, we examined the effects of ascorbic acid, at the six different doses, on penicillin-induced epileptiform activity. Methods: A single microinjection of penicillin (2.5 ,l, 500 units, intracortically) into the left sensorimotor cortex induced epileptiform activity within 2,5 min, progressing to full seizure activity lasting ,3,5 h. In the first set of experiments, 30 min after penicillin injection, six different doses of ascorbic acid (25, 50, 100, 200, 400, or 800 mg/kg) were administered intraperitoneally (IP). The other group of animals received the effective dose of ascorbic acid (100 mg/kg, IP) for 7 days. Ascorbic acid administration was stopped 24 h before penicillin treatment. Another group of rats received the effective dose of ascorbic acid (100 mg/kg, IP) 30 min before penicillin treatment. In the second set of experiments, the lipid peroxidation (MDA) and reduced glutathione (GSH) levels of brain were measured in the control, control + ascorbic acid, penicillin, and penicillin + ascorbic acid groups. Results: Ascorbic acid, at the low dose (50, 100 mg/kg, 30 min after penicillin injection), decreased both the frequency and amplitude of penicillin-induced epileptiform activity in rats. Ascorbic acid, at intermediate doses (200, 400 mg/kg, 30 min after penicillin injection), decreased the frequency of epileptiform activity without changing the amplitude. Ascorbic acid, at the lowest dose (25 mg/kg) and highest dose (800 mg/kg) (30 min after penicillin injection), did not change either the frequency or amplitude of epileptiform activity. Ascorbic acid, at the low dose (100 mg/kg) was the most effective dose in changing the frequency and amplitude of penicillin-induced epileptiform activity. Pretreatment with ascorbic acid (100 mg/kg) 30 min before penicillin treatment caused a significant delay in the onset of penicillin-induced epileptiform activity. Pretreatment with ascorbic acid (100 mg/kg) for 7 days did not change the latency of epileptiform activity. The most effective dose of ascorbic acid (100 mg/kg) prevented both the decrease in GSH level and the increase in lipid peroxidation level (MDA) occurring after penicillin-induced epileptiform activity. Conclusions: These data indicate that ascorbic acid has neuroprotective activity against penicillin-induced epileptiform electrocorticogram activity. [source] Base-Induced Formation of Two Magnesium Metal-Organic Framework Compounds with a Bifunctional Tetratopic LigandEUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 23 2008Pascal D. C. Dietzel Abstract Two coordination polymers constructed from magnesium and the tetratopic organic linker 2,5-dihydroxyterephthalic acid are reported, denominated CPO-26-Mg and CPO-27-Mg. The organic component carries two different types of protic functional groups. The degree of deprotonation of the organic component can be regulated by the amount of sodium hydroxide employed in the synthesis, thus determining which of the compounds forms. In CPO-26-Mg, only the carboxylic acid groups of the linker are deprotonated and take part in the construction of the three-dimensional framework. The structure is non-porous, and its topology is based on the PtS net. In CPO-27-Mg, both the carboxylic acid and the hydroxy groups are deprotonated and involved in the construction of a microporous three-dimensional framework which is based on a honeycomb motif containing large solvent-filled channels. The metal atoms are arranged in chiral chains along the intersection of the honeycomb and contain one water molecule in their coordination sphere, which allows for the creation of coordinatively unsaturated metal sites upon dehydration. CPO-27-Mg is a potentially useful lightweight adsorbent with a pore volume of 60,% of the total volume of the structure and an apparent Langmuir surface area of up to 1030 m2,g,1. Its thermal stability was investigated by thermogravimetry and variable-temperature powder X-ray diffraction, which shows framework degradation to commence at 160 °C in air, at 235 °C under nitrogen, and at 430 °C in a dynamic vacuum. Thermogravimetric dehydration and re-hydration experiments at miscellaneous temperatures indicate that it is possible to obtain open metal sites in CPO-27-Mg, but the water is more tightly bound in this material than in the previously reported isostructural nickel compound.(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008) [source] Neurite Outgrowth on Nanocomposite Scaffolds Synthesized from PLGA and Carboxylated Carbon Nanotubes,ADVANCED ENGINEERING MATERIALS, Issue 12 2009Hyun Jung Lee Abstract Carbon nanotubes (CNTs) have been suggested as suitable materials for biomedical applications, especially in the neural area. It is essential not only to investigate the biocompatibility of CNTs with the neural system but also to determine proper methods for applying CNTs to neuronal growth. This work represents the first application of CNTs by electrospun poly(D,L -lactic-co-glycolic acid) (PLGA) scaffolds for a neural system. We synthesized electrospun nanocomposites of PLGA and single-walled carbon nanotubes functionalized by carboxylic acid groups (c- SWNTs), and investigated neurite outgrowth from SH-SY5Y cells on these nanocomposites as compared to that on fibrous PLGA alone. Cells on our PLGA/c -SWNT nanocomposite showed significantly enhanced mitochondrial function and neurite outgrowth compared to cells on PLGA alone. We concluded that c -SWNTs incorporated into fibrous PLGA scaffolds exerted a positive role on the health of neural cells. [source] Combination of a hydroxy-functional organophosphorus oligomer and a multifunctional carboxylic acid as a flame retardant finishing system for cotton: Part II.FIRE AND MATERIALS, Issue 5 2003Formation of calcium salt during laundering Abstract Multifunctional carboxylic acids, such as 1,2,3,4-butanetetracarboxylic acid (BTCA), were used to bond a hydroxy-functional organophosphorus oligomer (FR) to cotton fabric in the presence of a catalyst, such as sodium hypophosphite (NaH2PO2). Previously, it was found that the cotton fabric treated with FR and BTCA showed a high level of phosphorus retention after one home laundering cycle. However, the flame retardant properties quickly deteriorated as the number of home laundering cycles was increased. In this research, it was found that the free carboxylic acid groups bound to the cotton fabric form an insoluble calcium salt during home laundering, thus diminishing the flame retardant properties of the treated cotton fabric. It was also found that the free carboxylic acid groups on the treated cotton fabric were esterified by triethanolamine (TEA), and that the formation of calcium salt on the fabric was suppressed by the esterification of the free carboxylic acid groups by TEA. The cotton fabric treated with BTCA and the hydroxy-functional organophosphorus oligomer significantly improved its flame retardance when a new catalyst system consisting of hypophosphorous acid (H3PO2) and TEA was used in the system. Copyright © 2003 John Wiley & Sons, Ltd. [source] A Reusable Interface Constructed by 3-Aminophenylboronic Acid-Functionalized Multiwalled Carbon Nanotubes for Cell Capture, Release, and CytosensingADVANCED FUNCTIONAL MATERIALS, Issue 6 2010Xue Zhong Abstract A newly developed electrochemical cell sensor for the determination of K562 leukemia cells using 3-aminophenylboronic acid (APBA)-functionalized multiwalled carbon nanotubes (MWCNTs) films is demonstrated. The films are generated by the covalent coupling between the NH2 groups in APBA and the COOH group in the acid-oxidized MWCNTs. As a result of the sugar-specific affinity interactions, the K562 leukemia cells are firmly bound to the APBA-functionalized MWCNTs film via boronic acid groups. Compared to electropolymerized APBA films, the presence of MWCNTs not only provides abundant boronic acid domains for cell capture, their high electrical conductivity also makes the film suitable for electrochemical sensing applications. The resulting modified electrodes are tested as cell detection sensors. This work presents a promising platform for effective cell capture and constructing reusable cytosensors. [source] Clean and Flexible Modification Strategy for Carboxyl/Aldehyde-Functionalized Upconversion Nanoparticles and Their Optical ApplicationsADVANCED FUNCTIONAL MATERIALS, Issue 24 2009Huan-Ping Zhou Abstract Rare-earth upconversion nanoparticles (UCNPs) exhibit great potential in luminescent biolabels and other multifunctional probes; however, their applications are limited by their low water solubility and the lack of binding groups. To address these problems, a clean and flexible strategy to modify hydrophobic monodisperse UCNPs into hydrophilic ones that are capped with functional groups is developed. The modification process is implemented by direct oxidation of oleic acid ligands with ozone under specific conditions, where the oleic acid (OA) ligands on the surface of the UCNPs can be converted into azelaic acid ligands (HOOC(CH2)7COOH) or azelaic aldehyde HOOC(CH2)7CHO, as is revealed by Fourier-transform infrared (FTIR) and nuclear magnetic resonance (NMR) measurements. This oxidation process has no significant side-effects on the morphology, phase, composition, or luminescent properties of the UCNPs. Free carboxylic acid groups on the surface endow the UCNPs with good water solubility, while aldehyde groups at the surface provide binding sites for amino-containing molecules via Schiff-base condensation, such as 2-(4-aminophenylethylyl)-5-methoxy-2-(2-pyridyl)thiazole (MPTEA) and 2-aminoethanethiol hydrochloride (NH2CH2CH2SH·HCl, HEMA). A Ce4+ sensor is constructed based on the dual-emission arising from the different spectral responses of MPTEA and the UCNPs. Facilitated by the covalent linkage between the terminal aldehyde group on the UCNPs and the amino group in HEMA, a hybrid structure of UCNPs and Au NPs is fabricated. The effective coupling between the aldehyde group and the amino group suggests that these functionalized UCNPs have potential in combining other functional units for simultaneous biolabeling, or other optical applications. [source] Specific Functionalization of Carbon Nanotubes for Advanced Polymer NanocompositesADVANCED FUNCTIONAL MATERIALS, Issue 24 2009Nanda Gopal Sahoo Abstract A novel approach to chemically functionalize multiwalled carbon nanotubes (MWCNTs) for making advanced polymeric nanocomposites with liquid crystalline polymers (LCPs) is presented. In this approach, two types of chemical moieties (i.e., carboxylic and hydroxyl benzoic acid groups) are selectively introduced onto the sidewalls of the MWCNTs. Fourier transform IR and Raman spectroscopy are used to examine the interaction between the functionalized MWCNTs and the LCP. The strong interaction between the functionalized MWCNTs and the LCP greatly improved the dispersion of MWCNTs in the polymer matrix as well as the interfacial adhesion. The dispersion of the MWCNTs in the LCP matrix is observed by optical microscopy and field-emission scanning electron microscopy. As a result, the addition of 1,wt% MWCNTs in the LCP resulted in the significant improvement (41 and 55%) in the tensile strength and modulus of the LCP. [source] Synthesis and Optoelectronic Properties of Nonpolar Polyrotaxane Insulated Molecular Wires with High Solubility in Organic Solvents,ADVANCED FUNCTIONAL MATERIALS, Issue 21 2008Michael J. Frampton Abstract Hydrophilic polyanionic conjugated polyrotaxanes are readily synthesized in water by Suzuki coupling, but their high polarity and ionic nature limit the potential applications of these materials. Here, we demonstrate three methods for transforming these polar polyelectrolytes into nonpolar lipophilic insulated molecular wires. A water-soluble polyfluorene- alt -biphenylene ,-cyclodextrin (CD) polyrotaxane was converted into nonpolar derivatives by methylation of the carboxylic acid groups with diazomethane and conversion of the hydroxyl groups of the CDs to benzyl ethers, trihexylsilyl ethers, benzoyl esters, and butanoate esters to yield polyrotaxanes that are soluble in organic solvents such as chloroform and cyclohexane. Elemental analysis, NMR spectroscopy, and gel permeation chromatography (GPC) data support the proposed structures of the organic-soluble polyrotaxanes. The extents of reaction of the polyrotaxane CD hydroxyl groups were 55% for trihexylsilyl chloride/imidazole; 81% for benzyl chloride/sodium hydride; 72% for benzoyl chloride/pyridine/4-dimethylaminopyridine; and 98% butanoic anhydride/pyridine/4-dimethylaminopyridine. Alkylation, silylation, and esterification increase the bulk of the encapsulating sheath, preventing interstrand aggregation, increasing the photoluminescence efficiency in the solid state and simplifying the time-resolved fluorescence decay. The organic-soluble polyrotaxanes were processed into polymer light-emitting diodes (PLEDs) from solution in nonpolar organic solvents, thereby excluding ionic impurities from the active layer. [source] Novel Solid Acid Catalysts: Sulfonic Acid Group-Functionalized Mesostructured Polymers,ADVANCED FUNCTIONAL MATERIALS, Issue 14 2007R. Xing Abstract Novel solid acid catalysts have been prepared from Fudan University (FDU)-type mesoporous polymers with the Ia d and P6mm mesostructures through a carefully controlled sulfonation procedure. Various techniques have been adopted to characterize throughout their structures, porosity, acidity as well as the information related to the sulfonic acid groups. The sulfonic acid group-functionalized mesopolymers prove to be efficient heterogeneous catalysts in the reactions such as liquid-phase Beckmann rearrangement of cyclohexanone oxime and condensation of ethylene glycol with the aldehydes having different molecular sizes. [source] The effect of ionic interaction on the miscibility and crystallization behaviors of poly(ethylene glycol)/poly(L -lactic acid) blendsJOURNAL OF APPLIED POLYMER SCIENCE, Issue 6 2008Wei-Chi Lai Abstract The effect of end groups (2NH2) of poly(ethylene glycol) (PEG) on the miscibility and crystallization behaviors of binary crystalline blends of PEG/poly(L -lactic acid) (PLLA) were investigated. The results of conductivity meter and dielectric analyzer (DEA) implied the existence of ions, which could be explained by the amine groups of PEG gaining the protons from the carboxylic acid groups of PLLA. The miscibility of PEG(2NH2)/PLLA blends was the best because of the ionic interaction as compared with PEG(2OH, 1OH-1CH3, and 2CH3)/PLLA blends. Since the ionic interaction formed only at the chain ends of PEG(2NH2) and PLLA, unlike hydrogen bonds forming at various sites along the chains in the other PEG/PLLA blend systems, the folding of PLLA blended with PEG(2NH2) was affected in a different manner. Thus the fold surface free energy played an important role on the crystallization rate of PLLA for the PEG(2NH2)/PLLA blend system. PLLA had the least fold surface free energy and the fast crystallization rate in the PEG(2NH2)/PLLA blend system, among all the PEG/PLLA systems studied. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008 [source] Synthesis of a new photoreactive gelatin with BTDA and HEMA derivativesJOURNAL OF APPLIED POLYMER SCIENCE, Issue 1 2008Fan-Chun Ding Abstract A novel bio-affinitive, photocuring, and membrane-forming gelatin derivative was synthesized in this study. This process was based on the amide formation between carboxylic acid and the amine in methanol,water media using dicyclohexyl-carbodiimide (DCC) as a condenser. Gelatin and glycine were the sources of amine in the model reaction. Since there were two anhydride groups in each 3,3,,4,4,-benzophenone tetra-carboxylic dianhydride (BTDA) molecule, two 2-hydroxyethyl methacrylate (HEMA) molecules were used to induce the ring-opening reaction of BTDA and release two carboxylic acid groups. The resulting photoreactive gelatin was called GE-BTHE, of which the photoreactive component was the ketone groups of BTDA and HEMA that played the role of double bond supplier. This photoreactive gelatin could be converted from the transparent liquid phase into swollen membrane by a 6-min irradiation of high pressure mercury lamp. The most efficient irradiation was at 267 nm and the highest degree of swelling of the cured GE-BTHE membrane could reach 5.9. The elongation from the dried gel remained 5,10%, i.e., relatively elastic. The properties of this gelatin derivative were investigated using amide formation analysis, calculation of the gel content and the swelling ratio, and monitoring of the photocuring process. The GE-BTHE synthesized in this study should be very potential in applications such as protective wound dressings and hemostatic absorbents for minimally invasive surgery. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008 [source] Comparison of specific interactions in P4VP/PSCA and PS4VP/PSCA blends and complexesJOURNAL OF APPLIED POLYMER SCIENCE, Issue 5 2008Naima Bouslah Abstract The compatibilization of an immiscible polymer system polystyrene/poly(4-vinylpyridine) has been induced by the introduction of carboxylic acid groups within the polystyrene chains. Poly(styrene- co -cinnamic acid), PSCA, copolymers were used to prepare blends and complexes with poly(4-vinylpyridine), P4VP, and in a second time with poly(styrene- co -4-vinylpyridine), PS4VP, copolymer in order to reduce the density of the interacting groups. The miscibility of the systems has been ascertained by DSC, which revealed that both blends and complexes exhibit a single glass transition temperature indicating their single phase nature. The Tgs of the complexes of PS4VP with PSCA15, containing 15 mol % of cinnamic acid content, were higher than those of the corresponding blends indicating that stronger interpolymer interactions were developed in the complexes. Furthermore, the application of the Kwei equation suggested that P4VP interacts more strongly with PSCA15 than does PS4VP. FTIR spectra revealed the development of hydrogen bonding within the PS4VP/PSCA system and both hydrogen bonding and ionic interaction in the P4VP/PSCA blends whereas the same interactions were expected in both systems. This observation confirmed the stronger ability of P4VP to interact with PSCA copolymer. The viscosimetric study showed both positive and negative deviations of the reduced viscosity of the blends from the additivity law confirming the presence of specific interactions within the blend solutions. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008 [source] FTIR, 1H-NMR spectra, and thermal characterization of water-based polyurethane/acrylic hybridsJOURNAL OF APPLIED POLYMER SCIENCE, Issue 2 2008O. R. Pardini Abstract Polyurethane (PU) polymer was synthesized following a prepolymer mixing process, by polyaddition of isophorone diisocyanate (IPDI), poly(propylene glycol) (PPG), 2-hydroxyethyl methacrylate (HEMA), and 2,2-bis(hydroxymethyl)propionic acid (DMPA). The PU anionomer having 2-ethoxymethacrylate terminal groups was dispersed in water by prior neutralization of carboxylic acid groups of DMPA with triethylamine (TEA), chain extended with hydrazine (HZM) in water and a dispersion polymerization with methyl methacrylate/n -butyl acrylate/acrylic acid mixture was performed. The above polymerization reactions lead to the formation of PU/acrylic hybrids having a chemical bond between PU and acrylic moieties. Acrylic content was varied from 0 to 50 wt % and samples were purified to eliminate oligomers and impurities before characterization. The FTIR and 1H-NMR spectra of these purified hybrid samples were obtained and bands and peaks assignments were discussed. Thermal properties (DSC and TGA) were also discussed. Breaking hydrogen bonds is the main reason for changes in properties with increasing acrylic content. Particle size data of dispersions is also presented and discussed. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008 [source] Characterization of end-functionalized styrene,butadiene,styrene copolymers and their application in modified asphaltJOURNAL OF APPLIED POLYMER SCIENCE, Issue 1 2007Qiang Wang Abstract End amino, carboxylic acid, and hydroxyl functionalized styrene,butadiene,styrene (SBS) triblock copolymers were prepared with 1,5-diazabicyclo[3.1.0]hexane, carbon dioxide, and epoxy ethane as capping agents, respectively. The effects of the end polar groups on the morphology and dynamic mechanical properties were investigated. Transmission electron microscopy images suggested that the group at the end of the polystyrene (PS) segment made the morphology of the PS domains disordered and incompact. Dynamic mechanical results showed that the storage and loss modulus increased after SBS was end-functionalized. End amino and carboxylic acid groups improved the compatibility and storage stability of SBS-modified asphalt. However, the effect of the end-hydroxyl group on the improvement of the storage stability of SBS-modified asphalt was not obvious. The differential scanning calorimetry analysis of SBS-modified asphalt further showed that the compatibility and storage stability of SBS-modified asphalt were improved by the attachment of amino or carboxylic acid groups through the anionic polymerization method. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 8,16, 2007 [source] Goitrogenic activity of p -coumaric acid in ratsJOURNAL OF BIOCHEMICAL AND MOLECULAR TOXICOLOGY, Issue 6 2003Fatima Khelifi-Touhami Abstract The effects of three natural phenolic acids (caffeic, ferulic, and p -coumaric) on the rat thyroid gland were examined in a 3-week oral-treatment study. Forty male Wistar albino rats, divided into groups of 10 rats each and fed iodine-rich diet, were administered by gastrointestinal tube saline (control), caffeic acid, ferulic acid, or p -coumaric acid at a dose level of 0.25 ,mol/kg/day for 3 weeks. The mean absolute and relative thyroid weights in caffeic, ferulic, or p -coumaric acid groups were significantly increased to 127 and 132%, 146 and 153%, or 189 and 201% compared to control value, respectively. Histological examination of the thyroids of p -coumaric acid group revealed marked hypertrophy and/or hyperplasia of the follicles. Caffeic or ferulic groups showed slight to moderate thyroid gland enlargement. Thyroid lesions in p -coumaric acid group were associated with significant increases in cellular proliferation as indicated by [3H]thymidine incorporation. In addition, the goitrogenic effect of p -coumaric acid was further confirmed by significant decreases (50%) in serum tri-iodothyronine (T3) and thyroxine (T4), and a parallel increase (90%) in serum thyroid stimulating hormone (TSH) compared to control group. These results indicate that administration of p -coumaric acid at relatively high doses induces goiter in rats. © 2003 Wiley Periodicals, Inc. J Biochem Mol Toxicol 17:324,328, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/jbt.10094 [source] Differential fragmentation patterns of pectin oligogalacturonides observed by nanoelectrospray quadrupole ion-trap mass spectrometry using automated spectra interpretationJOURNAL OF MASS SPECTROMETRY (INCORP BIOLOGICAL MASS SPECTROMETRY), Issue 4 2007Kudzai E. Mutenda Abstract Oligogalacturonides of different degrees of polymerization (DP) and methyl esterification (DE) were structurally analyzed by nanoESI quadrupole ion-trap mass spectrometry. The fragmentation patterns of the oligogalacturonides were compared using the program ,Virtual Expert Mass Spectrometrist' (VEMS) for structural annotation. In the analyzed oligogalacturonides of lower DP, the generation of C/Y ions, i.e. ions retaining the glycosidic oxygen, was higher than that of B/Z ions. In general, with oligogalacturonides of higher DP, the B/Z ions were generated more abundantly. Oligogalacturonides with free carboxylic acid groups underwent higher water loss compared to fully methyl-esterified oligogalacturonides under the same fragmentation conditions. Cross-ring cleavage, in which fragmentation occurs across the ring system of the galacturonate residue and signified by unique mass losses, was observed to be higher in fully methyl-esterified oligogalacturonides than in non-methyl-esterified ones. This study demonstrates the different fragmentation patterns of oligogalacturonides as influenced by the presence or absence of methyl ester groups. For a detailed analysis of unknown oligogalacturonides, cross-ring fragmentation gives more structural information than glycosidic bond cleavage. One implication of this is that more structural information is obtained when analyzing methyl-esterified oligogalacturonides than non-methyl-esterified ones in an ion-trap instrument. This is of particular importance in pectin chemistry, where mass spectrometry has become the technique of choice for structural determination. Although this study was not designed to explain the mechanisms of oligogalacturonide fragmentation, possible explanations for why non-methyl-esterified oligogalacturonides undergo more water loss than methyl-esterified ones will be postulated. In addition, the VEMS program was extended to automatically interpret and assign the fragment ions peaks generated in this study. Copyright © 2007 John Wiley & Sons, Ltd. [source] Application of solid-phase concentration-dependent HSDM to the acid dye adsorption systemAICHE JOURNAL, Issue 1 2005Vinci K. C. Lee Abstract The fixed-bed adsorption of acid dyes onto granular activated carbon (Chemviron Filtrasorb 400) has been studied using a homogeneous surface diffusion model (HSDM). The model incorporates the external boundary layer mass transport and homogeneous diffusion inside the particle. A new orthogonal collocation method has been developed and used to solve the diffusion equations. This orthogonal collocation gives a faster solution method compared with the numerical Crank,Nicolson method. The surface diffusivity has been determined by an optimization procedure with minimization of sum of the error squared. The equilibrium relationship between the liquid-phase concentration and the solid-phase concentration has been described by the Redlich,Peterson isotherm. A solid-phase concentration-dependent surface diffusivity was introduced. The Darken model with the Redlich,Peterson isotherm was found to be a suitable correlation model for the adsorption of the acid dyes on carbon. The magnitude of the averaged Ds0 of each dye is in the order of AR114 > AB80 > AY117, which implies that, under the same solid-phase concentration gradient, the rate of mass transport diffusion is higher in AR114 than that in AB80 and AY117. This phenomenon may be explained by the different mobilities of the dye molecules present in the solution by the different arrangements of two sulfonic acid groups in the dye structures. © 2004 American Institute of Chemical Engineers AIChE J, 51: 323-332, 2005 [source] Surface modification of poly(glycolic acid) (PGA) for biomedical applicationsJOURNAL OF PHARMACEUTICAL SCIENCES, Issue 5 2003Kyung-Bok Lee Abstract The immobilization of biological ligands (such as biotin and peptides) onto biodegradable polymer surfaces, including poly(glycolic acid) (PGA) sutures, is complicated by the absence of functional groups on the polymer backbone. We demonstrate a method for overcoming this problem, by attaching (+)-biotinyl-3,6,9-trioxaundecanediamine to the surface of PGA sutures, which immobilizes the ligand through an amide bond between amine (ligands) and carboxylic acid groups (surface-hydrolyzed PGA sutures). Fluorescence microscopy was used to verify the attachment of the biotin ligand to the surface of the PGA suture after a complexation with fluorescein-conjugated streptavidin. The strategy can be generalized to surface modifications of other biodegradable aliphatic polyesters, which would improve the properties of the polymers in biomedical applications such as active targeting of drugs based on ligand-attached, polymeric drug delvery systems. © 2003 Wiley-Liss, Inc. and the American Pharmaceutical Association J Pharm Sci 92:933,937, 2003 [source] Sulfonated polybenzimidazoles: Proton conduction and acid,base crosslinkingJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 16 2010Owen D. Thomas Abstract A series of soluble, benzimidazole-based polymers containing sulfonic acid groups (SuPBI) has been synthesized. SuPBI membranes resist extensive swelling in water but are poor proton conductors. When blended with high ion exchange capacity (IEC) sulfonated poly(ether ether ketone) (SPEEK), a polymer that has high proton conductivity but poor mechanical integrity, ionic crosslinks form reducing the extent of swelling. The effect of sulfonation of PBI on crosslinking in these blends was gauged through comparison with nonsulfonated analogs. Sulfonic acid groups present in SuPBI compensate for acid groups involved in crosslinking, thereby increasing IEC and proton conductivity of the membrane. When water uptake and proton conductivity were compared to the IEC of blends containing either sulfonated or nonsulfonated PBI, no noticeable distinction between PBI types could be made. Comparisons were also made between these blends and pure SPEEK membranes of similar IEC. Blend membranes exhibit slightly lower maximum proton conductivity than pure SPEEK membranes (60 vs. 75 mS cm,1) but had significantly enhanced dimensional stability upon immersion in water, especially at elevated temperature (80 °C). Elevated temperature measurements in humid environments show increased proton conductivity of the SuPBI membranes when compared with SPEEK-only membranes of similar IEC (c.f. 55 for the blend vs. 42 mS cm,1 for SPEEK at 80 °C, 90% relative humidity). © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 3640,3650, 2010 [source] Polynorbornene with pentafluorophenyl imide side chain groups: Synthesis and sulfonationJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 13 2010Arlette A. Santiago Abstract The mixtures of exo-endo -monomers and isomerically pure endo -monomers of N -pentafluorophenyl-norbornene-5,6-dicarboximide (2a) and N -phenyl-norbornene-5,6-dicarboximide (2b) were synthesized and polymerized via ring opening metathesis polymerization using bis(tricyclohexylphosphine) benzylidene ruthenium (IV) dichloride (I) and tricyclohexylphosphine [1,3-bis(2,4,6-trimethylphenyl)-4,5-dihydroimidazol-2-ylidene][benzylidene] ruthenium dichloride (II). Ring opening metathesis polymerization of mixtures of exo-endo -monomers (2a) and (2b) and pure endo - 2b gave the corresponding high molecular weights poly(N -pentafluorophenyl-norbornene-5,6-dicarboximide) (3a) and poly(N -phenyl-norbornene-5,6-dicarboximide) (3b). The isomerically pure endo - 2a did not polymerize by I in these conditions, since I is the least active catalyst and endo - 2a is the least active monomer because of the intramolecular complex formation between the Ru active center and the fluorine atom of ring-opened endo - 2a on the one hand and steric hindrances caused by the pentafluorinated ring on the other. The quantitative hydrogenation of the polymer 3a, at room temperature and 115 bar, was achieved by a Wilkinson's catalyst. The new polynorbornene bearing highly fluorinated sulfonic acid groups (5) was obtained by the reaction of the hydrogenated poly(N -pentafluorophenyl-norbornene-5,6-dicarboximide) (4) with sodium 4-hydroxybenzenesulfonate dihydrate. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 2925,2933, 2010 [source] A versatile approach for the syntheses of poly(ester amide)s with pendant functional groupsJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 15 2009Katelyn M. Atkins Abstract Poly(ester amide)s (PEAs) are emerging as promising materials for a wide range of biomedical applications due to their potential for both hydrolytic and enzymatic degradation, as well as the ease with which their properties can be tuned by the choice of monomers. The incorporation of pendant functional handles along the PEA backbone has the potential to further expand their applications by allowing the charge and hydrophilicity of the polymers to be altered, and facilitating the conjugation of active molecules such as drugs, targeting groups, and cell signaling molecules. Described here is a simple and versatile strategy based on orthogonal protecting groups, by which L -lysine and L- aspartic acid can be incorporated into several families of PEAs based on monomers including the diacids succinic and terephthalic acid, the diols 1,4-butanediol and 1,8-octanediol, and the amino acids L- alanine and L- phenylalanine. All polymers were thoroughly characterized by nuclear magnetic resonance spectroscopy, infrared spectroscopy, size exclusion chromatography, thermogravimetric analysis, and differential scanning calorimetry. It was demonstrated that the side chain protecting groups could be readily removed, allowing the pendant amines or carboxylic acids to be functionalized. In particular, the carboxylic acid groups on a polymer containing L- aspartic acid units were converted to N -hydroxysuccinimidyl esters, providing a useful template for further derivatization. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 3757,3772, 2009 [source] Synthesis, properties, and sulfonation of novel dendritic multiblock copoly(ether-sulfone)JOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 19 2008Sumiko Matsumura Abstract Multiblock copoly(ether-sulfone)s (PESs) bearing anchor units for the construction of dendritic blocks were synthesized by two-step reactions: (1) synthesis of PES block with both phenoxide end-groups; (2) chain extension and end-capping of the block by use of excess novel hexafunctional agent, hexakis(4-(4-fluorophenylsulfonyl)phenyl)benzene. The optimum average block length (n) and amount (x) of the hexafunctional agent used for the synthesis of high-molecular-weight PES without crosslinking were n = 26 and x = 2.6 equiv, respectively. The dendritic blocks in the PES were constructed by the aromatic nucleophilic substitution reaction of the activated aromatic fluoride groups on the anchor units using 4-tritylbenzenethiol. The clean substitution of the fluoride groups in the PES was confirmed by 1H NMR and 19F NMR. Three sulfonic acid groups were introduced on the pendant phenyl rings of the trityl groups in the PES by the reaction with chlorosulfonic acid. This is the first example of a dendritic PES bearing clusters of sulfonic acid groups only on the dendritic blocks. Cast films of presulfonated dendritic PES were strong and flexible, however, the membranes of sulfonated dendritic PES were brittle so that the conductivity measurements were not performed. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 6365,6375, 2008 [source] Synthesis and properties of polyimides bearing acid groups on long pendant aliphatic chainsJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 13 2006Tomohiro Yasuda Abstract A series of novel polyimide electrolytes having long pendant sulfo- or phosphoalkoxy groups were synthesized for fuel-cell applications. Sulfodecyloxy-, phosphodecyloxy-, and sulfophenoxydodecyloxy-substituted benzidine monomers were synthesized from dihydroxybenzidine. These monomers were copolymerized with naphthalene tetracarboxylic dianhydride and fluorenylidene dianiline to give the corresponding polyimides. A flexible, ductile, and self-standing membrane was obtained via casting from the polyimide solution. Because the acid groups were on long pendant side chains and away from the main chains, the polyimide membrane showed improved oxidative and hydrolytic stability in comparison with the polyimides with sulfonic acid groups on the main chains or on the short side chains. High thermal stability (no glass-transition temperature and a decomposition temperature > 200 °C) was also obtained. The polyimide membrane displayed high proton conductivity of 10,1 S cm,1 at 120 °C. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 3995,4005, 2006 [source] Synthesis of metal (Fe or Pd)/alloy (Fe,Pd)-nanoparticles-embedded multiwall carbon nanotube/sulfonated polyaniline composites by , irradiationJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 10 2006Kakarla Raghava Reddy Abstract Composites of multiwall carbon nanotubes (MWCNTs) and sulfonated polyaniline (SPAN) were prepared through the oxidative polymerization of a mixture of aniline, 2,5-diaminobenzene sulfonic acid, and MWCNTs. Fe, Pd, or Fe,Pd alloy nanoparticles were embedded into the MWCNT,SPAN matrix by the reduction of Fe, Pd, or a mixture of Fe and Pd ions with , radiation. Sulfonic acid groups and the emeraldine form of backbone units in SPAN served as the source for the reduction of the metal ions in the presence of , radiation. The existence of metallic/alloy particles in the MWCNT,SPAN matrix was further ascertained through characterization by high-resolution transmission electron microscopy (HRTEM), Fourier transform infrared spectroscopy, ultraviolet,visible spectroscopy, thermogravimetric analysis, and conductivity measurements. HRTEM pictures clearly revealed the existence of Fe, Pd, and Fe,Pd nanoparticles of various sizes in the MWCNT,SPAN matrices. There were changes in the electronic properties of the MWCNT,SPAN,M composites due to the interaction between the metal nanoparticles and MWCNT,SPAN. Metal-nanoparticle-loaded MWCNT,SPAN composites (MWCNT,SPAN,M; M = Fe, Pd, or Fe,Pd alloy) showed better thermal stability than the pristine polymers. The conductivity of the MWCNT,SPAN,M composites was approximately 1.5 S cm,1, which was much higher than that of SPAN (2.46 × 10,4 S cm,1). Metal/alloy-nanoparticle-embedded, MWCNT-based composite materials are expected to find applications in molecular electronics and other fields. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 3355,3364, 2006 [source] Improvement of ,-tocopherols long-term efficiency by modeling its heterogeneous natural environment in polyethyleneJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 5 2006Clara Strandberg Abstract The natural antioxidant vitamin E (,-tocopherol) is of interest to use in packaging applications to decrease the amount of toxic products migrating into food and drugs. We have earlier shown that the long-term efficiency of ,-tocopherol in polyethylene (PE) films is poor. ,-Tocopherol is located in the lipid phase of the cell in vivo and it has been revealed that it is more efficient in a polar substrate. PE is more hydrophobic and homogenous than the heterogeneous and hydrophilic lipid phase. Three different additive systems were investigated to model ,-tocopherols heterogeneous natural environment in PE. Two of these had carboxylic acid groups, EAA and polyTRIM/PAA core-shell particles (Core), and the third, oat starch, had no carboxylic acid groups. The materials were thermally aged and characterized by chemiluminescence (CL), FTIR, chromatography, and thermal analysis. The EAA system as well as the Core system improved the antioxidant properties of ,-tocopherol in PE, and the Core system had the best performance. We know that starch has stabilizing properties in PE, but it had no effect on the efficiency of ,-tocopherol. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 1660,1666, 2006 [source] | ||||||||||||||||||||||||||||||||||