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Maleic Acid (maleic + acid)

Distribution by Scientific Domains

Polymers and Materials Science	52%
Life Sciences	19%
Chemistry	19%

Selected Abstracts

On the Initial Stages of Electrooxidation of Aqueous Maleic Acid on Bi-Doped PbO2

ELECTROANALYSIS, Issue 15 2007
Carlos Borras
Abstract Oxidation of maleic acid in aqueous solution on bismuth-doped lead oxide has been studied. The effects of hydrodynamic conditions on the oxidation rate have been identified. The number of electrons transferred during the initial stages of oxidation as well as the apparent heterogeneous rate constant was obtained from the combined analysis of rotating ring-disk currents and the decrease of concentration at constant potential, determined from UV-vis measurements. The number of electrons involved during electrochemical oxidation was found to be 12, indicating full mineralization to CO2, and the heterogeneous rate constant for oxidation at 1.6,V was 9.8×105,cm s,1. [source]

Z and E isomers of butenedioic acid with 2-amino-1,3-thiazole: 2-amino-1,3-thiazolium hydrogen maleate and 2-amino-1,3-thiazolium hydrogen fumarate

ACTA CRYSTALLOGRAPHICA SECTION C, Issue 8 2010
Jain John
Maleic acid and fumaric acid, the Z and E isomers of butenedioic acid, form 1:1 adducts with 2-amino-1,3-thiazole, namely 2-amino-1,3-thiazolium hydrogen maleate (2ATHM), C3H5N2S+·C4H3O4,, and 2-amino-1,3-thiazolium hydrogen fumarate (2ATHF), C3H5N2S+·C4H3O4,, respectively. In both compounds, protonation of the ring N atom of the 2-amino-1,3-thiazole and deprotonation of one of the carboxyl groups are observed. The asymmetric unit of 2ATHF contains three independent ion pairs. The hydrogen maleate ion of 2ATHM shows a short intramolecular O,H...O hydrogen bond with an O...O distance of 2.4663,(19),Å. An extensive hydrogen-bonded network is observed in both compounds, involving N,H...O and O,H...O hydrogen bonds. 2ATHM forms two-dimensional sheets parallel to the ab plane, extending as independent parallel sheets along the c axis, whereas 2ATHF forms two-dimensional zigzag layers parallel to the bc plane, extending as independent parallel layers along the a axis. [source]

Characterization of Dicarboxylic Acids for Cellulose Hydrolysis

BIOTECHNOLOGY PROGRESS, Issue 3 2001
Nathan S. Mosier
In this paper, we show that dilute maleic acid, a dicarboxylic acid, hydrolyzes cellobiose, the repeat unit of cellulose, and the microcrystalline cellulose Avicel as effectively as dilute sulfuric acid but with minimal glucose degradation. Maleic acid, superior to other carboxylic acids reported in this paper, gives higher yields of glucose that is more easily fermented as a result of lower concentrations of degradation products. These results are especially significant because maleic acid, in the form of maleic anhydride, is widely available and produced in large quantities annually. [source]

On the Initial Stages of Electrooxidation of Aqueous Maleic Acid on Bi-Doped PbO2

Determination of ethyl sulfate , a marker for recent ethanol consumption , in human urine by CE with indirect UV detection

ELECTROPHORESIS, Issue 23 2006
Francesc A. Esteve-Turrillas
Abstract A CE method for the determination of the ethanol consumption marker ethyl sulfate,(EtS) in human urine was developed. Analysis was performed in negative polarity mode with a background electrolyte composed of 15,mM maleic acid, 1,mM phthalic acid, and 0.05,mM cetyltrimethylammonium bromide (CTAB) at pH,2.5 and indirect UV detection at 220,nm (300,nm reference wavelength). This buffer system provided selective separation conditions for EtS and vinylsulfonic acid, employed as internal standard, from urine matrix components. Sample pretreatment of urine was minimized to a 1:5 dilution with water. The optimized CE method was validated in the range of 5,700,mg/L using seven lots of urine. Intra- and inter-day precision and accuracy values, determined at 5, 60, and 700,mg/L with each lot of urine, fulfilled the requirements according to common guidelines for bioanalytical method validation. The application to forensic urine samples collected at autopsies as well as a successful cross-validation with a LC-MS/MS-based method confirmed the overall validity and real-world suitability of the developed expeditious CE assay (sample throughput 130 per day). [source]

Great Framework Variation of Polymers in the Manganese(II) Maleate/,,,,-Diimine System: Syntheses, Structures, and Magneto-Structural Correlation

EUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 15 2003
Chengbing Ma
Abstract Three novel manganese(II) coordination polymers, [Mn (maleate)(phen)]n (1; phen = 1,10-phenanthroline), [Mn(maleate)(phen)]n·nH2O (2), and [Mn(maleate)(bpy)]n (3; bpy = 2,2,-bipyridine), have been synthesized by treatment of Mn2+ with maleic acid with participation of chelate diimine ligands, and have been identified by single-crystal X-ray diffraction to have either one-dimensional (1D) zigzag chain structures (1 and 2) or a two-dimensional (2D) sinuous layer structure (3). Each maleate dianion coordinates to three Mn centers, in different bridging modes (syn - anti in 1 and 2, syn - syn and anti - anti in 3). These compounds represent an interesting example of structural topology variation from 1D to 2D mediated by chemically similar auxiliary chelate ligands. Variable-temperature magnetic susceptibility measurements show weak anti-ferromagnetic exchange interactions between the adjacent MnII ions, with J = ,0.06 cm,1 (2) and J = ,1.3 cm,1, zJ, = ,0.27 cm,1 (3). The differences in the magnitudes of these coupling interactions agree well with the nature of the carboxylate-bridging coordination of maleate. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003) [source]

Properties of amylopectin/montmorillonite composite films containing a coupling agent

JOURNAL OF APPLIED POLYMER SCIENCE, Issue 6 2007
D. Nordqvist
Abstract The addition of clay to polymers has the combined effects of enhancing both the strength/stiffness and the barrier properties. This investigation presents a novel approach to further enhance the strength/stiffness of cast plasticized amylopectin (AP)/Na+ -montmorillonite clay films using a water-soluble coupling agent, poly[(isobutylene- alt -maleic acid, ammonium salt)- co -(isobutylene- alt -maleic anhydride)], between the filler and the matrix. The addition of clay increased the strength and stiffness of the film and the addition of 0.4 parts of a coupling agent per 1 part clay further increased these properties. The trends were the same after each treatment, and there were always significant differences in stiffness and strength between the films without clay and with clay with 0.4 parts of the coupling agent. The increase in stiffness/strength in the presence of a small amount of the coupling agent suggested that it had a bridging effect, presumably through strong secondary bonds to the clay and to the matrix. Infrared spectroscopy and moisture swelling experiments indicated that ester bonds were formed between the coupling agent and AP. X-ray spectroscopy and transmission electron microscopy revealed that the clay-particle/polymer structure was qualitatively independent of the presence of the coupling agent showing a mixture of intercalated clay stacks and exfoliated platelets. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 104: 4160,4167, 2007 [source]

Establishment of Azotobacter on plant roots: chemotactic response, development and analysis of root exudates of cotton (Gossypium hirsutum L.) and wheat (Triticum aestivum L.)

JOURNAL OF BASIC MICROBIOLOGY, Issue 5 2007
Rakesh Kumar
Abstract Biofertilizers contribute in N2 fixation, P solubilization, phytohormone production and thus enhance plant growth. Beneficial plant-microbe interactions and the stability and effectiveness of biofertilizer depend upon the establishment of bacterial strains in the rhizosphere of the plant. This interaction depends upon many factors, one of them being plant exudates. Root exudates are composed of small organic molecules like carbonic acids, amino acids or sugars etc., which are released into the soil and bacteria can be attracted towards these exudates due to chemotaxis. The chemotactic behaviour of Azotobacter strains was studied using cotton (Desi HD 123 and American H 1098) and wheat (WH 711) seedlings and the root exudates of these two plants were chemically characterized. Analysis of the root exudates revealed the presence of sugars and simple polysaccharides (glucose), amino acids (glutamate, lysine) and organic acids (citric acid, succinic acid, maleic acid, malonic acid). Differences between cotton cultivars in root exudates were observed which influenced chemotactic response in Azotobacter. These results indicate colonization with rhizobacteria which implies that optimal symbionts, on the sides of both plant cultivar and bioinoculant bacteria can lead to better plant growth under cultivation conditions. (© 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]

Investigation of solute permeation across hydrogels composed of poly(methyl vinyl ether- co -maleic acid) and poly(ethylene glycol)

JOURNAL OF PHARMACY AND PHARMACOLOGY: AN INTERNATI ONAL JOURNAL OF PHARMACEUTICAL SCIENCE, Issue 7 2010
Thakur Raghu Raj Singh
Abstract Objectives, Swelling kinetics and solute permeation (theophylline, vitamin B12 and fluorescein sodium) of hydrogels composed of poly(methyl vinyl ether- co -maleic acid) (PMVE/MA) and poly(ethylene glycol) (PEG) are presented. Methods, The effects of PMVE/MA and PEG 10 000 content on swelling behaviour (percentage swelling, the type of diffusion and swelling rate constant) were investigated in 0.1 m phosphate buffer. Network parameters, such as average molecular weight between crosslinks (Mc) and crosslink density, were evaluated. Key findings, The percentage swelling and Mc of hydrogels increased with decrease in PMVE/MA content, where the water diffusion mechanism into the hydrogels was Class-II type. In contrast, increase in PMVE/MA content caused an increase in the crosslink density. Permeation of theophylline, vitamin B12 and fluorescein sodium, with increasing hydrodynamic radii, was studied through the equilibrium swollen hydrogels composed of PMVE/MA and PEG. In general, the permeability and diffusion coefficients of all three solutes decreased with increase in the PMVE/MA content. In addition, permeability and diffusion coefficient values increased with decreases in the hydrodynamic radii of the solute molecules. Conclusions, The hydrogels have shown a change in swelling behaviour, crosslink density, Mc and solute permeation with change in PMVE/MA content, thus suggesting a potential application in controlled drug-delivery systems. [source]

Ionic-Strength- and pH-Responsive Poly[acrylamide- co -(maleic acid)] Hydrogel Nanofibers

MACROMOLECULAR CHEMISTRY AND PHYSICS, Issue 8 2007
Haiqing Liu
Abstract A novel acrylamide/maleic acid copolymer [P(AM-MA)] hydrogel nanofibrous membrane with a fiber diameter of ca. 120 nm is prepared by electrospinning an aqueous P(AM-MA) solution with diethylene glycol as crosslinker, followed by a heat-induced esterification crosslinking reaction at 145,°C. This hydrogel nanofiber can maintain a fiber form, but becomes distorted and merges to form many physical crosslinking points after immersion in water. The P(AM-MA) hydrogel nanofibers are sensitive to external stimuli ionic strength and pH. Their water-swelling ratio decreases with increasing solution ionic strength, and it shows a characteristic two-step increase at pH,=,2.5 and 8.5 in response to the increase of solution pH. The maximum water-swelling ratios of the P(AM-MA) hydrogel nanofibers are 18.1 and 22.5 g,·,g,1 in a solution of 0.05 mol,·,dm,3 ionic strength and in an aqueous solution of pH 11, respectively. [source]

Preparation of Scratch- and Abrasion-Resistant Polymeric Nanocomposites by Monomer Grafting onto Nanoparticles, 4,

MACROMOLECULAR CHEMISTRY AND PHYSICS, Issue 3 2003
Frank Bauer
Abstract To obtain transparent, scratch- and abrasion-resistant coating materials a high content of nanosized silica and alumina filler was embedded in radiation-curable acrylate formulations by acid catalyzed silylation using trialkoxysilanes. 29Si magic angle spinning (MAS) NMR spectroscopy and matrix-assisted laser desorption/ionisation time-of-flight mass spectrometry (MALDI-TOF MS) were used to elucidate the structure of the surface-grafted methacryloxypropyl-, vinyl-, and n -propyltrimethoxysilane. 29Si MAS NMR measurements revealed a predominance of T2 and T3 structures of silicon atoms, i.e., silane oligomers have been formed by an extensive loss of water. For methacryloxypropyltrimethoxysilane, the proportion of the highly condensed T3 silicon atoms was estimated to be 75%. In accordance with these NMR findings, MALDI-TOF MS showed highly condensed oligomeric siloxanes of more than 20 monomeric silane units. The degree of silane condensation is higher on alumina than on silica, irrespective to the addition of maleic acid as catalyst. Moreover, completely condensed silsesquioxanes, e.g., octamers, decamers, and dodecamers, were detected. Based on the observed MS pattern, a ladder-like arrangement of two linked siloxane chains forming connected eight-membered rings is proposed, which is similar for all of the condensed organosilanes under study. The grafted polysiloxanes lead to an organophilation of inorganic nanofillers and improve their dispersibility in acrylate suspensions. Proposed ladder-like arrangement of the T3 structure of silicon atoms in polysiloxanes grafted on the silica surface. [source]

Novel Nanosized Aluminium Carboxylates: Synthesis, Characterization and Use as Nanofillers for Protective Polymeric Coatings

MACROMOLECULAR MATERIALS & ENGINEERING, Issue 1 2007
Hans-Jürgen Gläsel
Abstract A mixture of novel aluminium carboxylate nanoparticles and aluminium hydroxide ultrafine powder was prepared via precipitation reaction between Al(2-PrO)3 and maleic acid. In this mixture both free primary particles occur (mean geometrical size around 40 nm) together with a secondary agglomerated particle fraction of sizes in the low micrometer region. However, centrifugation processes allowed for the removal of the latter and resulted in the formation of size stable nanopowders. Up to 30 wt.-% of these particles were incorporated into acrylate matrices resulting in low-viscosity formulations with [,],<,1,000 mPa,·,s, which allowed for roller application and even spray coating of these nanocomposites at room temperature. Radiation curing of such coatings was accomplished via UV irradiation. In comparison to the corresponding SiO2 -based nanocomposites and carboxylate alumoxane fillers, the cured coatings revealed significantly improved surface mechanical properties. [source]

Brush-Like Amphoteric Poly[isobutylene- alt -(maleic acid)- graft -oligoethyleneamine)]/DNA Complexes for Efficient Gene Transfection

MACROMOLECULAR RAPID COMMUNICATIONS, Issue 13 2010
Majad Khan
Abstract Synthetic gene delivery vectors, especially cationic polymers have attracted enormous attention in recent decades because of their ease of manufacture, targettability, and scaling up. However, certain issues such as high cytotoxicity and low transfection efficiency problems have hampered the advance of nonviral gene delivery. In this study, we designed and synthesized brush-like amphoteric poly[isobutylene- alt -(maleic acid)- graft -oligoethyleneamine] capable of mediating highly efficient gene transfection. The polymers are composed of multiple pendant oligoethyleneimine molecules with alternating carboxylic acid moiety grafted onto poly[isobutylene- alt -(maleic anhydride)]. The polymer formed from pentaethylenehexamine {i.e., poly[isobutylene- alt -(maleic acid)- graft -pentaethylenehexamine)]} was able to condense DNA efficiently into nanoparticles of size around 200,nm with positive zeta potential of about 28,30,mV despite its amphoteric nature. Luciferase expression level and percentage of GFP expressing cells induced by this polymer was higher than those mediated with polyethyleneimine (branched, 25,kDa) by at least one order of magnitude at their optimal N/P ratios on HEK293, HepG2, and 4T1 cells. In vitro cytotoxicity testing revealed that the polymer/DNA complexes were less cytotoxic than those of PEI, and the viability of the cells after being incubated with the polymer/DNA complexes at the optimal N/P ratios was higher than 85%. This polymer can be a promising gene delivery carrier for gene therapy. [source]

Spectroscopic and thermal studies of poly[(N -vinylimidazole)- co -(maleic acid)] hydrogel and its quaternized form

POLYMER INTERNATIONAL, Issue 4 2008
Nursel Pekel
Abstract BACKGROUND: In this study, poly[(N -vinylimidazole)- co -(maleic acid)] (poly(VIm/MA)) hydrogels were prepared by ,-irradiation of ternary mixtures of N -vinylimidazole,maleic acid,water using a 60Co ,-source. Spectroscopic and thermal analyses of these hydrogels as a function of protonation showed that the results are consistent with the existence of an H-bridged complex when the imidazole rings are partially protonated. Finally, the efficiency and binding trends of Cu2+, Co2+, Cd2+ and Pb2+ ions with both protonated and unprotonated poly(VIm/MA) hydrogels were determined. RESULTS: Gelation of 90% was reached at around 180 kGy dose at the end of irradiation. The poly(VIm/MA) hydrogels synthesized were further protonated in HCl solutions with different concentrations. Hydrogels originally showed 450% volumetric swelling; this ratio reached 1900% after protonation at pH = 5.0. Fourier transform infrared spectral changes in the +NH stretching region (3200,3600 and 1173 cm,1) and the ring mode deformation at 915 cm,1 are consistent with the formation of an H-bridged complex between the protonated and unprotonated imidazole rings upon partial protonation. Similar changes were obtained from NMR spectra of both the protonated and unprotonated forms of the hydrogels. CONCLUSION: Protonated and unprotonated hydrogels have been used in heavy metal ion adsorption studies for environmental purposes. Adsorption decreased with decreasing pH value due to the protonation of the VIm ring. The adsorption of Me2+ ions decreased in the order Cu2+ > Co2+ > Cd2+ > Pb2+, which is related to the complexation stability as well as the ionic radius of the metal ions. These results show that P(VIm/MA) hydrogels can be used efficiently to remove heavy metal ions from aqueous solutions. However, the protonated form is a bad choice for heavy metal ion adsorption due to electrostatic repulsion forces; it can nevertheless be assumed to be a good choice for anion adsorption from environmental waste water systems. Copyright © 2007 Society of Chemical Industry [source]

Hydrogen-bonding interaction of an alternating maleic acid,vinyl acetate copolymer with poly(ethylene glycol), polyacrylamide and poly(N -isopropylacrylamide): a comparative study

POLYMER INTERNATIONAL, Issue 12 2003
C Vasile
Abstract The hydrogen-bonding interaction and interpolymer complex formation between an alternating maleic acid,vinyl acetate copolymer, (MAc- alt -VA) and poly(ethylene glycol) (PEG), polyacrylamide (PAM) or poly(N -isopropylacrylamide) (PNIPAM) in aqueous solution was potentiometrically and viscometrically investigated. MAc- alt -VA formed with PEG a strong hydrogen-bonding interpolymer complex with a compact structure, and while its interaction with PAM seems to be very weak, if any, the complex formed with PNIPAM is even stronger than that with PEG. This indicates a very important contribution of hydrophobic interaction to the formation of such hydrogen-bonding interpolymer complexes. Copyright © 2003 Society of Chemical Industry [source]

Hyperbranched macromolecules through donor-acceptor type copolymerization of allyl,vinylene bifunctional monomers,

POLYMER INTERNATIONAL, Issue 10 2002
O Rzaev, Zakir M
Abstract Present review is an attempt to generalize and systematize the results accumulated in synthesis of cyclolinear and hyperbranched reactive macromolecules via radical alternating copolymerization of various bifunctional monomers containing donor and acceptor type double bonds. Synthesis of hyperbranched reactive macromolecules was carried out using complex-radical cyclocopolymerization of donor-acceptor type bifunctional monomers such as monoallyl ester of maleic acid (MAM), allyl acrylate (AA), allyl methacrylate (AM), allyl trans -cinnamate (AC), methylallylmaleate (MeAM), methylallylfumarate (MAF) and allyl-,-(N-maleimido)acetate (AMI), and maleic anhydride (MA) and styrene (St) as typical acceptor and donor comonomers, respectively. The kinetic parameters of these reactions, constants of cyclization, complex-formation and copolymerization, as well as the ratios of chain growth rates for the participation of monomeric charge transfer complexes and free monomers, were all determined. It was demonstrated that in the studied systems, copolymerizations predominantly proceed according to alternating mechanism with formation of macromolecules having cyclolinear structure in the steady-state and hyperbranched structure in the high conversion conditions. It was shown that formation of linear and hyperbranched macromolecules containing allyl or vinylene groups in the side chain occurs selectively carry out and depends on the nature of used comonomer. General schemes and proposed mechanism of hyperbranching and crosslinking reactions were also described. Some useful properties of synthesized reactive copolymers were discussed. © 2002 Society of Chemical Industry. [source]