Acrylic Acid (acrylic + acid)

Distribution by Scientific Domains
Distribution within Polymers and Materials Science

Terms modified by Acrylic Acid

  • acrylic acid monomer

  • Selected Abstracts

    Synthesis of Well-Defined Statistical and Diblock Copolymers of Acrylamide and Acrylic Acid by Inverse Miniemulsion Raft Polymerization

    Liu Ouyang
    Abstract Well-defined statistical and diblock copolymers with acrylamide and acrylic acid were synthesized by inverse miniemulsion RAFT polymerization. Statistical copolymers with various composition ratios were synthesized. Compositional drift was observed during polymerization. Acrylamide was polymerized with a water-soluble initiator (VA-044) at 60,C to give the RAFT-agent-containing acrylamide homopolymer with a narrow molecular-weight distribution (PDI,<,1.3), which was then chain-extended with acrylic acid to obtain the diblock copolymer. [source]

    PLP-SEC Study into the Free-Radical Propagation Rate Coefficients of Partially and Fully Ionized Acrylic Acid in Aqueous Solution

    Igor Lack
    Abstract Summary: Propagation rate coefficients, kp, for acrylic acid (AA) polymerization at 6,C in aqueous solution were measured via pulsed laser polymerization (PLP) with the degree of ionization, ,, varied over the entire range between 0 and 1. These measurements were carried out in conjunction with aqueous-phase size-exclusion chromatography (SEC). Strictly speaking, the reported kp's are "apparent" propagation rate coefficients deduced from the PLP-SEC data under the assumption that the local monomer concentration at the radical site is identical to overall monomer concentration. At an AA concentration of 0.69 mol,,L,1, the apparent kp decreases from 111,000 L,,mol,1,,s,1 at ,,=,0 to 13,000 L,,mol,1,,s,1 at ,,=,1.0. The significant lowering of kp with higher , is attributed to the repulsion between both monomer molecules and macroradicals becoming negatively charged. Addition of up to 10 mol-% (with respect to AA) sodium hydroxide to the fully ionized aqueous AA solution leads to an enhancement of kp up to 57,000 L,,mol,1,,s,1. Dependence of apparent kp values on the degree of ionization of acrylic acid (a) and on pH (b) for aqueous polymerizations of acrylic acid. [source]

    Study on the Graft Reaction of Poly(propylene) Fiber with Acrylic Acid

    Wei Wang
    Abstract Summary: In this paper, the graft of poly(propylene) fiber with acrylic acid is investigated. The effects of grafting temperature, monomer concentration, and grafting time on the grafting degree of acrylic acid onto poly(propylene) fiber are discussed. In contrast to the conventional method of determining the grafting degree gravimetrically, the acid-base titration method used in this paper was more efficient, even at low grafting degree. High-performance liquid chromatography (HPLC) was used to estimate the averaged length of the grafted poly(acrylic acid) chains on each grafted site of poly(propylene) backbone. And also a mechanism for the grafting polymerization is proposed. Possible microstructures of two PP-g-AA samples at the same grafting degree. [source]

    Reply to: "Testing the Hypothesis: Comments on Plasma Polymerization of Acrylic Acid Revisited"

    Dirk Hegemann
    Abstract We reply to the discussions started by Rob Short and David Steele concerning the use of a macroscopic approach to examine the plasma polymerization of acrylic acid. Therefore, we analyze data of mass deposition rates versus the reaction parameter W/F using Arrhenius-type plots, which were recorded in different plasma reactors used by Short et al. and our group. [source]

    PE-CVD of Acid/Base Coatings from Acrylic Acid and Allylamine Vapours

    Eloisa Sardella
    Abstract Different plasma processes were investigated to obtain coatings characterized by N and O functional groups at their surface. From the literature, big efforts are evident devoted to designing new surfaces with chemical composition and chemical,physical properties tightly controlled. This paper demonstrates how it is possible to obtain coatings with acid and basic properties at different extent, by simply adjusting the acrylic acid/allylamine chemical composition of the gas feed in a plasma deposition process. The deposited films exhibit tuneable acid,base properties, very attractive to manufacture sensors, and biomaterials, and for applications in tissue engineering field. [source]

    ChemInform Abstract: Base-Catalyzed Conjugate Addition of Thiols to Indolyl Acrylic Acids and in situ Decarboxylation: An Expedient Synthesis of Functionalized 3-(1-Thio)ethyl-1H-indoles.

    CHEMINFORM, Issue 17 2010
    Shijay Gao
    Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a "Full Text" option. The original article is trackable via the "References" option. [source]

    ChemInform Abstract: Synthesis of Functionalized ,-Pyrone and Butenolide Derivatives by Rhodium-Catalyzed Oxidative Coupling of Substituted Acrylic Acids with Alkynes and Alkenes.

    CHEMINFORM, Issue 2 2010
    Satoshi Mochida
    Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a "Full Text" option. The original article is trackable via the "References" option. [source]

    The Interaction of Heteroaryl-Acrylates and Alanines with Phenylalanine Ammonia-Lyase from Parsley

    Csaba Paizs Dr.
    Abstract Acrylic acids and alanines substituted with heteroaryl groups at the ,-position were synthesized and spectroscopically characterized (UV, HRMS, 1H NMR, and 13C NMR spectroscopy). The heteroaryl groups were furanyl, thiophenyl, benzofuranyl, and benzothiophenyl and contained the alanyl side chains either at the 2- or 3-positions. While the former are good substrates for phenylalanine ammonia-lyase (PAL), the latter compounds are inhibitors. Exceptions are thiophen-3-yl-alanine, a moderate substrate and furan-3-yl-alanine, which is inert. Possible reasons for these exceptions are discussed. Starting from racemic heteroaryl-2-alanines their D -enantiomers were prepared by using a stereodestructive procedure. From the heteroaryl-2-acrylates, the L -enantiomers of the heteroaryl-2-alanines were prepared at high ammonia concentration. These results can be best explained by a Friedel,Crafts-type electrophilic attack at the aromatic part of the substrates as the initial step of the PAL reaction. [source]

    Application of hydrophilic finished of synthetic fabrics coated with CMC/acrylic acid cured by electron beam irradiation in the removal of metal cations from aqueous solutions

    Sayeda M. Ibrahim
    Abstract Modified textile fabrics were used to remove Cu+2 and Cr+3 ions from aqueous solutions. For this purpose, modified Nylon-6, polyester woven and knitted fabrics were prepared by coating the surface with a thin layer of aqueous solution of carboxymethyl cellulose (CMC) and acrylic acid (AAc) of thickness 25 ,m. Radiation crosslinking of the coated layer was carried out by electron beam irradiation with a constant dose of 30 kGy. Morphology of the coated fabrics was examined by scanning electron microscope (SEM) which indicated the compatibility between the coated layer and fabrics. Properties attributed to the hydrophilicity, especially water uptake and weight loss before and after several washing cycles were followed up. The effect of AAc concentration on the hydrophilic properties of the coated fabrics was studied. A considerable enhancement in water uptake has been attained on increasing AAc content in solution in case of nylon-6 followed by polyester woven followed by polyester knitted fabrics. The performances of the modified textile fabrics were evaluated for the recovery of Cu+2 and Cr+3 from aqueous solution. The metal ion absorption efficiency of the modified textile fabrics was measured using UV Spectrophotometer analysis and EDX. Parameters affecting the efficiency of these textile fabrics in the removal of metal ions from aqueous solution namely, concentration of AAc and the immersion time were studied. It was found that there was a marked increase in the recovery of metal ions on increasing both immersion time and concentration of AAc. This study evidences that the modified textile fabrics can be used for the purpose of removal of some heavy metals such as Cu and Cr. 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010 [source]

    Empirical Modeling of Butyl Acrylate/Vinyl Acetate/Acrylic Acid Emulsion-Based Pressure-Sensitive Adhesives

    Renata Jovanovic
    Abstract Summary: Butyl acrylate/vinyl acetate/acrylic acid (BA/VAc/AA) emulsion latexes were produced in a semi-batch mode. The objective was to generate polymers with properties favoring their application as pressure-sensitive adhesives. The influence of the individual monomer concentrations on final properties such as glass transition temperature (Tg), peel strength, shear strength and tack was investigated. To obtain the maximum amount of information in a reasonable number of runs, a constrained three-component mixture design was used to define the experimental conditions. Latexes were coated onto a polyethylene terephthalate carrier and dried. Different empirical models (e.g. linear, quadratic and cubic mixture models) governing the individual properties (i.e. Tg, peel adhesion, shear resistance and tack) were developed and evaluated. In the given experimental region, no single model was found to fit all of the responses (i.e. the final properties). However, in all models the most significant factor affecting the final properties was the AA concentration, followed by the VAc concentration. Shear strength contour lines over the investigated region. [source]

    Using the Aggregation of Latex Polymers in the Fabrication of Reproducible Enzyme Electrodes

    ELECTROANALYSIS, Issue 17 2003
    Wibowo Rahmat
    Abstract An enzyme electrode for glucose is described as a model system to demonstrate a fabrication method using latex aggregation and entrapment of enzyme. Electrosterically-stabilized latex particles synthesized by emulsion polymerization in batch from acrylic acid, methyl methacrylate and butyl acrylate, and glucose oxidase were coagulated together at pH,5.5 with ethanol. A platinum disk electrode dipped in the solution becomes coated with latex/enzyme. The relative thickness of the film and relative amount of enzyme may be controlled by the time the electrode is in contact with the solution. The enzyme was then immobilized by covalent attachment of amine groups to carboxylic moieties in the polymer using 1-ethyl-3(3-dimethylaminopropyl)-carbodiimide hydrochloride and N -hydroxysuccinimide. Five minutes contact with the latex/enzyme solution and subsequent amide coupling, gave electrodes with a reproducibility of 5.7% RSD, a wide dynamic range (0,100,mM) and good storage properties. [source]

    Interaction of Zoospores of the Green Alga Ulva with Bioinspired Micro- and Nanostructured Surfaces Prepared by Polyelectrolyte Layer-by-Layer Self-Assembly

    Xinyu Cao
    Abstract The interaction of spores of Ulva with bioinspired structured surfaces in the nanometer,micrometer size range is investigated using a series of coatings with systematically varying morphology and chemistry, which allows separation of the contributions of morphology and surface chemistry to settlement (attachment) and adhesion strength. Structured surfaces are prepared by layer-by-layer spray-coating deposition of polyelectrolytes. By changing the pH during application of oppositely charged poly(acrylic acid) and polyethylenimine polyelectrolytes, the surface structures are systematically varied, which allows the influence of morphology on the biological response to be determined. In order to discriminate morphological from chemical effects, surfaces are chemically modified with poly(ethylene glycol) and tridecafluoroctyltriethoxysilane. This chemical modification changes the water contact angles while the influence of the morphology is retained. The lowest level of settlement is observed for structures of the order 2,m. All surfaces are characterized with respect to their wettability, chemical composition, and morphological properties by contact angle measurement, X-ray photoelectron spectroscopy, scanning electron microscopy, and atomic force microscopy. [source]

    Production of d -(,)-3-hydroxyalkanoic acid by recombinant Escherichia coli

    Kai Zhao
    Abstract Pathways for extracellular production of chiral d -(,)-3-hydroxybutyric acid (3HB) and d -(,)-3-hydroxyalkanoic acid (mcl-3HA) were constructed by co-expression of genes of ,-ketothiolase (phbA), acetoacetyl-CoA reductase (phbB) and 3-hydroxyacyl-ACP CoA transacylase (phaG), respectively, in Escherichia coli strain DH5,. The effect of acrylic acid and glucose on production of both 3HB and mcl-3HA was investigated. It was found that the addition of acrylic acid significantly increased production of 3HB and mcl-3HA consisting of 3-hydroxyoctanoic acid and 3-hydroxydecanoic acid in a ratio of 1:3 from 199 mg l,1 to 661 mg l,1 and from 27 mg l,1 to 135 mg l,1, respectively, in shake flask studies when glucose was present in the medium at the very beginning of fermentation. The timing of glucose addition had no effect on 3HB production. In contrast, mcl-3HA production was affected by glucose addition, an mcl-3HA concentration of 193 mg l,1 was obtained when glucose was added to the culture at 12 h. A more than seven-fold increase was obtained when compared with that in medium containing glucose at the beginning of fermentation. However, a decrease in production of 3HB and mcl-3HA was found when glucose was added at 12 h to the culture containing acrylic acid. The repressive effect of acrylic acid on acetic acid production was also evaluated and discussed. [source]

    Quantum-Dot-Functionalized Poly(styrene- co -acrylic acid) Microbeads: Step-Wise Self-Assembly, Characterization, and Applications for Sub-femtomolar Electrochemical Detection of DNA Hybridization

    Haifeng Dong
    Abstract A novel nanoparticle label capable of amplifying the electrochemical signal of DNA hybridization is fabricated by functionalizing poly(styrene- co -acrylic acid) microbeads with CdTe quantum dots. CdTe-tagged polybeads are prepared by a layer-by-layer self-assembly of the CdTe quantum dots (diameter,=,3.07,nm) and polyelectrolyte on the polybeads (diameter,=,323,nm). The self-assembly procedure is characterized using scanning and transmission electron microscopy, and X-ray photoelectron, infrared and photoluminescence spectroscopy. The mean quantum-dot coverage is (9.54,,1.2),,103 per polybead. The enormous coverage and the unique properties of the quantum dots make the polybeads an effective candidate as a functionalized amplification platform for labelling of DNA or protein. Herein, as an example, the CdTe-tagged polybeads are attached to DNA probes specific to breast cancer by streptavidin,biotin binding to construct a DNA biosensor. The detection of the DNA hybridization process is achieved by the square-wave voltammetry of Cd2+ after the dissolution of the CdTe tags with HNO3. The efficient carrier-bead amplification platform, coupled with the highly sensitive stripping voltammetric measurement, gives rise to a detection limit of 0.52 fmol L,1 and a dynamic range spanning 5 orders of magnitude. This proposed nanoparticle label is promising, exhibits an efficient amplification performance, and opens new opportunities for ultrasensitive detection of other biorecognition events. [source]

    Preparation of Uniform, Water-Soluble, and Multifunctional Nanocomposites with Tunable Sizes

    Dechao Niu
    Abstract Novel, thiol-functionalized, and superparamagnetic, silica composite nanospheres (SH-SSCNs) with diameters smaller than 100,nm are successfully fabricated through the self-assembly of Fe3O4 nanoparticles and polystyrene100 - block -poly(acrylic acid)16 and a subsequent sol-gel process. The size and magnetic properties of the SH-SSCNs can be easily tuned by simply varying the initial concentrations of the magnetite nanoparticles in the oil phase. By incorporating fluorescent dye molecules into the silica network, the composite nanospheres can be further fluorescent-functionalized. The toxicity of the SH-SSCNs is evaluated by choosing three typical cell lines (HUVEC, RAW264.7, and A549) as model cells, and no toxic effects are observed. It is also demonstrated that SH-SSCNs can be used as a new class of magnetic resonance imaging (MRI) probes, having a remarkably high spin,spin (T2) relaxivity (r2*,=,176.1,mM,1 S,1). The combination of the sub-100-nm particle size, monodispersity in aqueous solution, superparamagnetism, and fluorescent properties of the SH-SSCNs, as well as the non-cytotoxicity in vitro, provides a novel and potential candidate for an earlier MRI diagnostic method of cancer. [source]

    Preparation and Characterization of a pH- and Thermally Responsive Poly(N -isopropylacrylamide- co -acrylic acid)/Porous SiO2 Hybrid

    Loren A. Perelman
    Abstract A multifunctional nanohybrid composed of a pH- and thermoresponsive hydrogel, poly(N -isopropylacrylamide- co -acrylic acid) [poly(NIPAM- co -AAc)], is synthesized in situ within the mesopores of an oxidized porous Si template. The hybrid is characterized by electron microscopy and by thin film optical interference spectroscopy. The optical reflectivity spectrum of the hybrid displays Fabry,Prot fringes characteristic of thin film optical interference, enabling direct, real-time observation of the pH-induced swelling, and volume phase transitions associated with the confined poly(NIPAM- co -AAc) hydrogel. The optical response correlates to the percentage of AAc contained within the hydrogel, with a maximum change observed for samples containing 20% AAc. The swelling kinetics of the hydrogel are significantly altered due to the nanoscale confinement, displaying a more rapid response to pH or heating stimuli relative to bulk polymer films. The inclusion of AAc dramatically alters the thermoresponsiveness of the hybrid at pH 7, effectively eliminating the lower critical solution temperature (LCST). The observed changes in the optical reflectivity spectrum are interpreted in terms of changes in the dielectric composition and morphology of the hybrids. [source]

    Time Controlled Protein Release from Layer-by-Layer Assembled Multilayer Functionalized Agarose Hydrogels

    Sumit Mehrotra
    Abstract Axons of the adult central nervous system exhibit an extremely limited ability to regenerate after spinal cord injury. Experimentally generated patterns of axon growth are typically disorganized and randomly oriented. Support of linear axonal growth into spinal cord lesion sites has been demonstrated using arrays of uniaxial channels, templated with agarose hydrogel, and containing genetically engineered cells that secrete brain-derived neurotrophic factor (BDNF). However, immobilizing neurotrophic factors secreting cells within a scaffold is relatively cumbersome, and alternative strategies are needed to provide sustained release of BDNF from templated agarose scaffolds. Existing methods of loading the drug or protein into hydrogels cannot provide sustained release from templated agarose hydrogels. Alternatively, here it is shown that pH-responsive H-bonded poly(ethylene glycol)(PEG)/poly(acrylic acid)(PAA)/protein hybrid layer-by-layer (LbL) thin films, when prepared over agarose, provided sustained release of protein under physiological conditions for more than four weeks. Lysozyme, a protein similar in size and isoelectric point to BDNF, is released from the multilayers on the agarose and is biologically active during the earlier time points, with decreasing activity at later time points. This is the first demonstration of month-long sustained protein release from an agarose hydrogel, whereby the drug/protein is loaded separately from the agarose hydrogel fabrication process. [source]

    Dual-Tone Patterned Mesoporous Silicate Films Templated From Chemically Amplified Block Copolymers

    Sivakumar Nagarajan
    Abstract Directly patterned mesoporous silicate films are prepared using positive- and negative-tone strategies by performing phase selective silica condensation within lithographically exposed poly(styrene- b - tert -butyl acrylate) (PS- b -PtbA) templates containing photoacid generators. The use of supercritical fluid as a process medium enables rapid diffusion of the silicate precursor within the prepatterned block copolymer template film without disrupting its morphology. Template exposure through the mask triggers area selective generation of acid, which in turn both deprotects the poly(tert -butyl acrylate) block to yield a poly(acrylic acid) block and provides a catalyst for silica precursor condensation yielding pattern formation at the device level. Because the acid generated in the UV exposed field preferentially segregates into hydrophilic poly(acrylic acid) domains of the phase segregated, deprotected block copolymer, precursor condensation is simultaneously controlled at nanoscopic length scales via templating by the underlying block copolymer morphology. The ability of PS- b -PtbA to undergo chemical transformation in two stages, deprotection followed by crosslinking, enables precise replications of the photomask in positive and negative tones. Detemplating via calcination yields patterned mesoporous silicate films without etching. Template formulations are optimized using infrared spectroscopic studies and the silicate films are characterized using electron microscopy and scanning force microscopy. [source]

    Bifurcated Mechanical Behavior of Deformed Periodic Porous Solids

    Srikanth Singamaneni
    Abstract The transformation of periodic microporous structures fabricated by interference lithography followed by their freezing below glass transition is described. Periodic porous microstructures subjected to internal compressive stresses can undergo sudden structural transformation at a critical strain. The pattern transformation of collapsed pores is caused by the stresses originated during the polymerization of acrylic acid (rubbery component) inside of cylindrical pores and the subsequent solvent evaporation in the organized microporous structure. By confining the polymerization of acrylic acid to localized porous areas complex microscopic periodic structures can be obtained. The control over the mechanical instabilities in periodic porous solids at a sub-micron scale demonstrated here suggests the potential mechanical tunability of photonic, transport, adhesive, and phononic properties of such periodic porous solids. [source]

    A General Strategy to Disperse and Functionalize Carbon Nanotubes Using Conjugated Block Copolymers

    Jianhua Zou
    Abstract A general strategy to disperse and functionalize pristine carbon nanotubes in a single-step process is developed using conjugated block copolymers. The conjugated block copolymer contains two blocks: a conjugated polymer block of poly(3-hexylthiophene), and a functional non-conjugated block with tunable composition. When the pristine carbon nanotubes are sonicated with the conjugated block copolymers, the poly(3-hexylthiophene) blocks bind to the surface of de-bundled carbon nanotubes through non-covalent ,,, interactions, stabilizing the carbon nanotube dispersion, while the functional blocks locate at the outer surface of carbon nanotubes, rendering the carbon nanotubes with desired functionality. In this paper, conjugated block copolymers of poly(3-hexylthiophene)- b -poly(methyl methacrylate), poly(3-hexylthiophene)- b -poly(acrylic acid), and poly(3-hexylthiophene)- b -poly(poly(ethylene glycol) acrylate) are used to demonstrate this general strategy. [source]

    Selective Immobilization of Protein Clusters on Polymeric Nanocraters,

    A. Valsesia
    Abstract A method for fabricating chemically nanopatterned surfaces based on a combination of colloidal lithography and plasma- enhanced chemical vapor deposition (PECVD) is presented. This method can be applied for the creation of different nanopatterns, and it is in principle not limited in patterning resolution. Nanocraters of poly(acrylic acid) (carboxylic moieties) surrounded by a matrix of poly(ethylene glycol) are fabricated. Chemical force microscopy demonstrates that the process is able to produce the expected surface chemical contrast. Finally, the carboxylic groups of the craters are activated in order to induce the covalent binding of fluorescent-labeled proteins. Fluorescence investigation using scanning confocal microscopy shows that the proteins are preferentially attached inside the functional craters. [source]

    Cover Picture: Hierarchically Organized Superstructure Emerging from the Exquisite Association of Inorganic Crystals, Organic Polymers, and Dyes: A Model Approach Towards Suprabiomineral Materials (Adv. Funct.

    Abstract Suprabiomineral materials possessing hierarchically organized superstructures are investigated by Imai and Oaki on p.,1407. Inorganic crystals, organic polymers, and functional dyes have assembled via a simple biomimetic route into a superstructure that contains six different tiers, from the macroscale to the nanoscale. The hierarchy originates from the strong interaction between crystals and polymers and the diffusion-controlled conditions. The versatile role of the polymer is found to be essential for the construction of a superstructure. This approach promises to generate novel types of functional materials with controllable structures and properties. We report a novel hierarchically organized superstructure emerging from an exquisite association of inorganic crystals, organic polymers, and dyes. The resultant K2SO4/poly(acrylic acid) composite includes five different tiers from the nanoscopic to the macroscopic. An additional new tier leading to functionality is formed by the incorporation of organic dyes that are organized in a nanospace. The emergent superstructure and properties are designed through changes in polymer concentration. The multiple roles of the polymer realize the generation of the architecture at each size scale. This model approach should be widely applicable to other systems, allowing for the preparation of innovative materials by an appropriate combination of crystals, polymers, and functional molecules. [source]

    Cover Picture: Synthesis of Gadolinium-Labeled Shell-Crosslinked Nanoparticles for Magnetic Resonance Imaging Applications (Adv. Funct.

    Abstract Robust, amphiphilic core,shell nanoparticles that are selectively labeled with gadolinium in the hydrophilic and water-swollen shell layer are depicted in the cover picture. These well-defined nanostructured materials exhibit high relaxivity, a large loading capacity, and are based upon a biocompatible platform for ultimate function in magnetic resonance imaging (MRI) applications, as reported by Wooley and co-workers on p.,1248. Shell-crosslinked knedel-like nanoparticles (SCKs; "knedel" is a Polish term for dumplings) were derivatized with gadolinium chelates and studied as robust magnetic-resonance-imaging-active structures with hydrodynamic diameters of 40,,3,nm. SCKs possessing an amphiphilic core,shell morphology were produced from the aqueous assembly of diblock copolymers of poly-(acrylic acid) (PAA) and poly(methyl acrylate) (PMA), PAA52,b,PMA128, and subsequent covalent crosslinking by amidation upon reaction with 2,2,-(ethylenedioxy)bis(ethylamine) throughout the shell layer. The properties of these materials, including non-toxicity towards mammalian cells, non-immunogenicity within mice, and capability for polyvalent targeting, make them ideal candidates for utilization within biological systems. The synthesis of SCKs derivatized with GdIII and designed for potential use as a unique nanometer-scale contrast agent for MRI applications is described herein. Utilization of an amino-functionalized diethylenetriaminepentaacetic acid,Gd analogue allowed for direct covalent conjugation throughout the hydrophilic shell layer of the SCKs and served to increase the rotational correlation lifetime of the Gd. In addition, the highly hydrated nature of the shell layer in which the Gd was located allowed for rapid water exchange; thus, the resulting material demonstrated large ionic relaxivities (39,s,1,mM,1) in an applied magnetic field of 0.47,T at 40,C and, as a result of the large loading capacity of the material, also demonstrated high molecular relaxivities (20,000,s,1,mM,1). [source]

    Electroactivity of Polyaniline Multilayer Films in Neutral Solution and Their Electrocatalyzed Oxidation of ,-Nicotinamide Adenine Dinucleotide

    S. Tian
    Abstract In this paper, we report an alternative simple method to shift the electroactivity of polyaniline (PANI) films to neutral pH conditions by forming multilayer assemblies with poly(anions) using the layer-by-layer (LBL) deposition method. A series of self-assembled PANI multilayer films with poly(anions), such as sulfonated polyaniline (SPANI), poly(acrylic acid) (PAA), poly(vinyl sulfonate) (PVS), and poly(styrene sulfonate) (PSS), were prepared by the LBL method. Their electrochemical behavior and catalytic ability for the oxidation of ,-nicotinamide adenine dinucleotide (NADH) in neutral solution were investigated by electrochemistry (EC) combined with surface plasmon spectroscopy (SPS) and the quartz crystal microbalance (QCM) technique. Results indicated that all the films showed very good stability, reversibility, and electroactivity in neutral solution. All the multilayer films can electrocatalyze the oxidation of NADH, with the catalytic ability of PANI/SPANI being higher than that of the other assemblies under the same conditions. The catalytic abilities of the films with the same thickness prepared by the copolymerization method and the LBL method were also compared. [source]

    Fabrication of Reactivated Biointerface for Dual-Controlled Reversible Immobilization of Cytochrome c

    ADVANCED MATERIALS, Issue 43 2009
    Pengbo Wan
    A light or pH dual-responsive reactivated biointerface is fabricated using of photocontrolled reversible inclusion and exclusion reactions between photoresponsive azobenzene-containing self-assembled monolayer and pH-responsive poly(acrylic acid) polymer grafted with cyclodextrins. The dual-controlled reactivated biointerface can be employed for reversible immobilization of redox protein,Cytochrome c, triggered by dual external stimuli-light and pH. [source]

    Properties of Porous Si3N4/BN Composites Fabricated by RBSN Technique

    Ji-Xuan Liu
    Reaction bonding of silicon nitride (RBSN) technique combined with slip-casting shaping process was used to fabricate porous Si3N4/BN ceramic composites. Si/BN slurry with chemical stability, good dispersibility, and viscosity was prepared using glycerol trioleate (GTO) covering on Si surface and poly(acrylic acid) (PAA) as dispersant. The hydrolysis of Si was strongly prevented by GTO coating. The dispersibility of covered Si and BN suspensions were improved by PAA dispersant. Twenty volume percent covered Si/BN slurries with low viscosity were successfully casted. The cast bodies were dried at room temperature, debindered at 750C and nitrided below 1450C. The nitrided samples mainly consist of ,-Si3N4, ,-Si3N4, and h-BN. The composites exhibit homogeneous microstructure consisting of faceted particles, ,-Si3N4 nanowires and a large amount of pores. The porosity is 52.64% and the pore size is in the range of 60,300 nm. The composites show compressive strength of 16.61.5 MPa. The dielectric constant of the composite is about 3.1 and the dielectric loss is below 0.5% under different frequencies. [source]

    Multilayer Nanocomplexes of Polymer and DNA Exhibit Enhanced Gene Delivery,

    ADVANCED MATERIALS, Issue 1 2008
    M. Saul
    Polymeric-DNA complexes (polyplexes) are constructed with multiple layers of counter-polyions as DNA/polyethylenimine/poly(acrylic acid)/polyethylenimine. The increased association of polyethylenimine achieved by the multilayer approach leads to substantial increases in expression of transgene for reporter plasmids without the need for excess free polymer typically required for non-viral gene delivery. This method of polyplex preparation provides the opportunity to improve transgene expression for gene therapy approaches to disease treatment. [source]

    Kinetics of the synthesis of propyl and butyl acrylates in the presence of some heteropolyacids as catalysts

    Jerzy Skrzypek
    Esterification reactions of acrylic acid with n -propanol and n -butanol were carried out in the liquid phase in the presence of H3PW12O40 or H3PMo12O40 as a catalyst, at various temperatures, molar ratios of the reactants, and concentrations of the catalyst. The kinetic equations had a nonelementary form. 2008 Wiley Periodicals, Inc. Int J Chem Kinet 41: 12,17, 2009 [source]

    Kinetics and mechanism of esterification of epoxy resin in presence of triphenylphosphine

    Neelam Pal
    The kinetics of esterification of bisphenol-A based epoxy resin with acrylic acid in presence of triphenylphosphine has been studied. The reaction exhibits a first-order rate dependence with respect to [Epoxy] and [Catalyst]. A first-order dependence of rate with respect to [Acid] has been observed during a particular kinetic run. However, a retarding effect of [Acid] on the rate has been observed by increasing the initial concentration of acid. A suitable mechanism consistent with the kinetic data is proposed and discussed. 2004 Wiley Periodicals, Inc. Int J Chem Kinet 36: 280,285, 2004 [source]

    Regioselective and Enantioselective Hydroformylation of Dialkylacrylamides


    Abstract Dimethylacrylamide can be hydroformylated with very high chemo- and regioselectivity. Asymmetric hydroformylation of this substrate is possible, provided steps are taken to minimise racemisation of the aldehyde products, and this work demonstrates the effect of various conditions and variables on racemisation. Using the Landis diazaphospholane ligands up to 68% ee can be realised under very mild conditions. Other dialkylacrylamides were also hydroformylated under mild conditions giving similar or better enantioselectivities, including the Weinreb amide of acrylic acid (71% ee), and the asymmetric hydroformylation of diethylacrylamide producing the chiral aldehyde with up to 82% ee. [source]