Showing papers on "Acrylic acid published in 2002"

Layered, erasable polymer multilayers formed by hydrogen-bonded sequential self-assembly

Abstract: Robust multilayers can be formed on solid surfaces, and subsequently destroyed by changing the environmental conditions, by the layer-by-layer sequential assembly of monomolecular films of a polyacid and polybase from aqueous solution. Interlayer hydrogen bonding produces stable multilayers up to the point where altered pH or other environmental stimulus introduces an unacceptably large electrical charge within them. This is demonstrated for the polyacids poly(acrylic acid), PAA, and poly(methacrylic acid), PMAA, and for the polybases poly(vinylpyrrolidone), PVPON, and poly(ethylene oxide), PEO, in D2O. The adsorption was quantified by Fourier transform infrared spectroscopy in attenuated total reflection (FTIR-ATR). The ratio between suppressed ionization of the carboxylic groups within the film and their ionization in solution, as directly measured by FTIR-ATR, was used to estimate the fraction of hydrogen-bonded carboxylic groups; this was ∼0.5 in PVPON/PMAA but only ∼0.1 in the PEO/PMAA system, though...

Micropatterning of Polymer Thin Films with pH-Sensitive and Cross-linkable Hydrogen-Bonded Polyelectrolyte Multilayers

Abstract: Polyelectrolyte multilayers of poly(acrylic acid) (PAA) and polyacrylamide (PAAm) were prepared via hydrogen-bonding interactions. These multilayers as assembled were stable at low pH but dissolved quickly in neutral pH water. We developed methods for stabilizing these multilayers to high pH through cross-linking by heating or UV-irradiation. Thermal treatment of the multilayers, which resulted in a partial imidization between carboxylic acid and amide groups, gave the multilayer good stability at high pH. In addition, we introduced photoreactive groups in the multilayer, which rendered the film insoluble after UV irradiation. Using these selective stabilization approaches, we have succeeded in micropatterning these films by ink-jet printing and photolithography to create subtractive patterns.

Polyelectrolyte Multilayer Nanoreactors for Preparing Silver Nanoparticle Composites: Controlling Metal Concentration and Nanoparticle Size

Abstract: The size of in situ prepared silver nanoparticles and the overall metal concentration within poly(acrylic acid) (PAA) and poly(allylamine hydrochloride) (PAH) multilayer films are systematically co...

Integration of polyaniline/poly(acrylic acid) films and redox enzymes on electrode supports: an in situ electrochemical/surface plasmon resonance study of the bioelectrocatalyzed oxidation of glucose or lactate in the integrated bioelectrocatalytic systems.

Abstract: Electropolymerization of aniline in the presence of poly(acrylic acid) on Au electrodes yields a polyaniline/poly(acrylic acid) composite film, exhibiting reversible redox functions in aqueous solutions at pH = 7.0. In situ electrochemical-SPR measurements are used to identify the dynamics of swelling and shrinking of the polymer film upon the oxidation of the polyaniline (PAn) to its oxidized state (PAn(2+)) and the reduction of the oxidized polymer (PAn(2+)) back to its reduced state (PAn), respectively. Covalent attachment of N(6)-(2-aminoethyl)-flavin adenin dinucleotide (amino-FAD, 1) to the carboxylic groups of the composite polyaniline/poly(acrylic acid) film followed by the reconstitution of apoglucose oxidase on the functional polymer yields an electrically contacted glucose oxidase of unprecedented electrical communication efficiency with the electrode: electron-transfer turnover rate approximately 1000 s(-1) at 30 degrees C. In situ electrochemical-SPR analyses are used to characterize the bioelectrocatalytic functions of the biomaterial-polymer interface. The current responses of the bioelectrocatalytic system increase as the glucose concentrations are elevated. Similarly, the SPR spectra of the system are controlled by the concentration of glucose. The glucose concentration controls the steady-state concentration ratio of PAn/PAn(2+) in the film composition. Therefore, the SPR spectrum of the film measured upon its electrochemical oxidation is shifted from the spectrum typical for the oxidized PAn(2+) at low glucose concentration to the spectrum characteristic of the reduced PAn at high glucose concentration. Similarly, the polyaniline/poly(acrylic acid) film acts as an electrocatalyst for the oxidation of NADH. Accordingly, an integrated bioelectrocatalytic assembly was constructed on the electrode by the covalent attachment of N(6)-(2-aminoethyl)-beta-nicotinamide adenine dinucleotide (amino-NAD(+), 2) to the polymer film, and the two-dimensional cross-linking of an affinity complex formed between lactate dehydrogenase and the NAD(+)-cofactor units associated with the polymer using glutaric dialdehyde as a cross-linker. In situ electrochemical-SPR measurements are used to characterize the bioelectrocatalytic functions of the system. The amperometric responses of the system increase as the concentrations of lactate are elevated, and an electron-transfer turnover rate of 350 s(-1) between the biocatalyst and the electrode is estimated. As the PAn(2+) oxidizes the NADH units generated by the biocatalyzed oxidation of lactate, the PAn/PAn(2+) steady-state ratio in the film is controlled by the concentration of lactate. Accordingly, the SPR spectrum measured upon electrochemical oxidation of the film is similar to the spectrum of PAn(2+) at low lactate concentration, whereas the SPR spectrum resembles that of PAn at high concentrations of lactate.

Fluorochemical sulfonamide surfactants

Abstract: Described are fluorochemical surfactants derived from nonafluorobutanesulfonyl fluoride that contain polyalkyleneoxy side chains and may be copolymerized with acrylic acid or methacrylic acid to form polyacrylates or polymethacrylates. The surfactants surprisingly lower the surface tension of water and other liquids in the same or similar low values achieved by premier surfactants such as those derived from perfluorooctane sulfonyl fluoride.

Synthesis and characterisation of a polyacrylamide-polyacrylic acid copolymer hydrogel for environmental analysis of Cu and Cd

Abstract: A polyacrylamide–polyacrylic acid copolymer hydrogel was prepared by the controlled hydrolysis of polyacrylamide in an alkaline solution of 10% sodium hydroxide. The structure and composition of the resulting copolymer hydrogel was approximately two acrylic acid units for every acrylamide unit. The capacity of the copolymer hydrogel to bind various metal ions was tested under a range of uptake conditions, with varying uptake time, pH and ionic strength. Ions such as Cu 2+ and Cd 2+ were bound more strongly to the copolymer hydrogel than the competing ions of Na + , K + , Ca 2+ and Mg 2+ , particularly at pH>5, largely due to the increased acidity of these transition metal ions. Metals bound to the copolymer hydrogel were efficiently (>94%) eluted in 2 M HNO 3 solution. The copolymer was found to have a p K a of ∼4.5 and had an equilibrium swelling ratio of 120 at pH>6 with an ionic strength equivalent to 0.01 M NaCl, and a swelling ratio of 265 at low ionic strengths. This material should be of use for the recovery and separation of Cu 2+ and Cd 2+ ions, and trace environmental analysis applications such as the diffusive gradients in thin films (DGT) technique.

Poly(ethylene oxide) coated surfaces

Abstract: Methods are provided for the fabrication of hydrophilic coatings on hydrophobic surfaces. In one embodiment, a polyethylene oxide (PEO) coating is fabricated on the surface of a polymeric material by contacting the surface with a methacrylic acid or acrylic acid monomer. The monomer first is reacted, for example by irradiation with an electron beam, to polymerize and covalently attach the monomer to the surface, to improve the hydrophilicity of the polymeric material. A coating of PEO molecules is subsequently attached to the polymer surface by hydrogen bond complexation. The PEO coating then may be covalently grafted onto the surface, for example, by irradiation grafting with an electron beam. The covalent grafting of a coating of the methacrylic or acrylic monomers to the surface greatly improves the wettability of the surface, and facilitates the covalent or non-covalent attachment of a coating of PEO to the polymer surface. Thus, hydrophilic PEO coatings can be fabricated on hydrophobic polymer surfaces, to improve the biocompatibility and other properties of the polymer surfaces.

Synthesis and Characterization of Poly(acrylic acid)-graft-poly(vinylidene fluoride) Copolymers and pH-Sensitive Membranes

Abstract: Molecular modification of ozone-pretreated poly(vinylidene fluoride) (PVDF) via thermally induced graft copolymerization with acrylic acid (AAc) in N-methyl-2-pyrrolidone (NMP) solution was carried...

Dually Responsive Microgels from Polyether-Modified Poly(acrylic acid): Swelling and Drug Loading

Abstract: Gel microparticles composed of lightly cross-linked poly(acrylic acid) networks, onto which polyether chains (Pluronic F127) are grafted, are introduced. The hydrophobic poly(propylene oxide) chains aggregate within the microgel structure, and the resulting aggregates are capable of solubilizing hydrophobic drugs, such as taxol. At temperatures where the Pluronic chains are not aggregated, the microgels behave like networks without spatial heterogeneity. Upon formation of aggregates within hydrogels, their equilibrium swelling diminishes, and the swelling behavior indicates non-Gaussian chain distribution. The kinetics of gel swelling shows unusual temperature dependence of the effective diffusion coefficient, indicative of chain rearrangement within a certain temperature range. The microgels exhibit high ion-exchange capacity for cationic hydrophilic drugs. The potential for the newly obtained microgels to be used as drug carriers is discussed.

Continuous method for the production and purification of (meth)acrylic acid

Abstract: The invention relates to a method for the purification of (meth)acrylic acid comprising a stage which consists of the following steps a) (meth) acrylic acid is crystallized from a mother liquor; b) crystallized (meth) acrylic acid is separated from the mother liquor; c) at least one part of the separated (meth)acrylic acid crystals is melted; d) the melted part is at least partially returned to step a) or b). The inventive method, the device suitable for carrying out said method and the use of the inventive device for the production of (meth) acrylic acid are characterized by the high purity of the (meth) acrylic acid thus obtained, and high efficiency with regard to the desired yield and amount of energy required.

Synthesis and characterization of branched polyelectrolytes. 1. Preparation of hyperbranched poly(acrylic acid) via self-condensing atom transfer radical copolymerization

Abstract: We report on the synthesis of randomly branched (arborescent) poly(acrylic acid) (PAA) by self-condensing vinyl copolymerization (SCVCP) of an acrylic AB* inimer, 2-(2-bromopropionyloxy)ethyl acryl...

Thermosensitive Poly(N-isopropylacrylamide-co-acrylic acid) Hydrogels with Expanded Network Structures and Improved Oscillating Swelling−Deswelling Properties

Abstract: In this paper, a P(NIPAAm-co-AAc) hydrogel with rapid temperature sensitivity and improved oscillatory properties over small temperature cycles around the physiologic temperature of 37 °C was synth...

The Effect of Fatty Acid Composition on the Acrylation Kinetics of Epoxidized Triacylglycerols

Abstract: Epoxidized oils, epoxidized triacylglycerols, and epoxidized fatty acid methyl esters were made by reaction with performic acid formed in situ. The extent of epoxidation was ca. 95% for all of the epoxidized samples, as determined by 1H nuclear magnetic resonance. The epoxidized samples were reacted with an excess of acrylic acid for different reaction times. The acrylation reaction was found to have a first-order dependence on the epoxide concentration for all oils, pure triacylglycerols, and fatty acid methyl esters. However, the rate constant of acrylation was found to depend on the composition of the epoxidized material. The acrylation rate constant for 9,10-epoxystearic acid was 96 L2/(mol2·min). The rate constant of acrylation for the epoxides on 9,10,12,13-diepoxystearic acid was 60 L2/(mol2·min). The acrylation rate constant for the epoxides on 9,10,12,13,15,16-triepoxystearic acid was 50 L2/(mol2·min). Thus, the rate constant of acrylation increased as the number of epoxides per fotty acid decreased. Multiple epoxides per fatty acid decrease the reactivity of the epoxides because of steric hindrance effects, and the oxonium ion, formed as an intermediate during the epoxyacrylic acid reaction, is stabilized by local epoxide groups. These results were used to derive an acrylation kinetic model that predicts rate constants from fatty acid distributions in the oil. The predictions of the model closely match the experimentally determined rate constants.

Thermoresponsive Ultrathin Hydrogels Prepared by Sequential Chemical Reactions

Abstract: Thermoresponsive ultrathin hydrogels were prepared by the sequential chemical reaction of poly(vinylamine-co-N-vinylisobutyramide) [poly(VAm-co-NVIBA)] and poly(acrylic acid) (polyAAc) on a gold surface. The carboxyl group of polyAAc was activated by 1-ethyl-3-(3-(dimethylamino)propyl)carbodiimide hydrochloride (EDC) for the reaction with the amino group of poly(VAm-co-NVIBA) to yield the amide linkage. This stepwise assembly was analyzed quantitatively by a quartz crystal microbalance (QCM), which revealed that the 39 mol % VAm content of poly(VAm-co-NVIBA) was suitable for the preparation of ultrathin hydrogels. A detailed analysis was performed by the assembly of poly(VAm-co-NVIBA), with a 39 mol % VAm content and polyAAc. The reflection−absorption spectra (RAS) showed the presence of both polymers in the assembly. Atomic force microscopic (AFM) observations confirmed the hydrogel structure of the assembly; the thickness of the hydrogel in an aqueous medium (around 320 nm) was 2 times greater than that...

Preparation of styrene/acrylic acid copolymer microspheres: polymerization mechanism and carboxyl group distribution

Abstract: Poly(styrene-co-acrylic acid) (St/AA) copolymer microspheres were prepared by batch emulsifier-free emulsion copolymerization of St with AA. The monomer conversion, the morphology and the composition of the particles along the polymerization process were monitored by a gravimetric method, transmission electron microscopy observation and Fourier transform IR analysis, respectively. A shift of the polymerization locus from inside the particles to “outside” the particles in the postnucleation stage was proposed. The results of the study of the distribution of carboxyl groups by a combination of elemental and X-ray photoelectron spectroscopy analyses implied a core/shell structure for the St/AA copolymer microspheres. By chemical metal deposition, nickel particles were formed and deposited on the surface of St/AA microspheres, forming polymer/metal composite particles.

UV-Based Patterning of Polymeric Substrates for Cell Culture Applications

Abstract: We studied the physico/chemical effects of deep UV irradiation of polystyrene, polymethylmethacrylate and polycarbonate with respect to cell adhesion in vitro. Photochemical modifications of the polymer surfaces yielded active peroxide compounds which allowed graft coupling of acrylic monomers (acrylamide, acrylic acid) together with oxidized chemical groups which were identified by X-ray photoelectron spectroscopy, dye binding and contact angle titrations as being mainly carboxylic groups. It was observed that hepatocytes (HepG2, human hepatoma cell line) and fibroblasts (L929, murine cell line) exhibit strong adhesion on the irradiated polymer surfaces. Masked irradiations opened a simple, fast, and economical route to obtain chemically patterned polymeric substrates for structured cell adhesion. This is more advantageous as compared to silane based patterning techniques on glass or thiol based patterning on gold due to the elimination of any chemical treatment, the clean room compatibility and the small size of achieved structures. The described cell patterning technique may become a useful tool for the study of a variety of defined co-cultures (for example hepatocytes and fibroblasts), neuronal networks, intercellular communication, organogenesis and for applications like biosensors or engineered highly functional tissues and implants as bioartificial organs.

Equilibrium Swelling of Copolymerized Acrylic Acid−Methacrylated Dextran Networks: Effects of pH and Neutral Salt

Abstract: In this study, pH-responsive dextran hydrogels were prepared by radical copolymerization of methacrylated dextran (MA-dextran) with acrylic acid (AAc) in aqueous solution, using ammonium peroxydisu...