Showing papers on "Acrylic acid published in 2001"

Coated medical devices

Abstract: An implantable medical device carries on at least part of its external surface a coating. The coating consists essentially of aterpolymer of vinyl pyrrolidone, acrylic acid and activated acrylic acid, and optionally a colouring agent.

Nanoporous thin films formed by salt-induced structural changes in multilayers of poly(acrylic acid) and poly(allylamine).

Abstract: We report here on the influence of changes in the solution salt concentration on the structure of multilayers of weak polyelectrolytes. For poly(acrylic acid) (PAA) and poly(allylamine) (PAH) multilayers assembled by the layer-by-layer process in the presence of sodium chloride, washing with pure water after deposition of each layer produces films with considerable surface roughness (root-mean-squared (rms) roughness ∼17 nm for a 10 layer film), as assessed by scanning force microscopy. In contrast, relatively smooth (rms roughness ∼1 nm) and homogeneous PAH/PAA multilayer films are formed when the salt concentration is kept constant both during the assembly process and in the washing steps. For such smooth films, subsequent exposure to pure water leads to the introduction of regular, discrete, nanometer-sized pores, thus providing a means of introducing lateral structure into the PAH/PAA multilayer films. Electrochemical measurements revealed that the pores formed in less than 10 min. The sensitivity of ...

Synthesis and Properties of Poly(acrylic acid)/Mica Superabsorbent Nanocomposite

Abstract: A novel poly(acrylic acid)/mica super absorbent composite was synthesized by graft polymerization reaction betwen partially neutralized acrylic acid and ultrafine mica mineral powder. The water absorbency of the composite is higher than 1 100 g H2O/g. The influence of the neutralization degree of acrylic acid, as well as of the amounts of mica and crosslinker on the absorbing properties are discussed in this paper.

Selective oxidation of propane to acrylic acid with molecular oxygen

Abstract: This review covers the recent developments and the present state of selective oxidation of propane to acrylic acid with molecular oxygen. The current commercial manufacturing process of acrylic acid, as well as the possible oxidation pathways of propane are included as background information. Special attention is given to three classes of leading catalysts: vanadium pyrophosphate, heteropoly acids and salts and mixed metal oxides. Topics covered include the development and the effectiveness of the catalyst systems, the oxidation pathways, and some structural aspects.

Acrylic acid doped polyaniline as an ammonia sensor

Abstract: Chemically synthesised acrylic acid doped polyaniline (PANI:AA) has been utilised as an ammonia vapour sensor in a broad range of concentrations, viz. 1–600 ppm. The response, in terms of decrease in dc electric resistance on exposure to ammonia was observed. The change in resistance, ΔR, is found to increase linearly with NH3 concentration upto 58 ppm and saturates thereafter. The decrease in resistance has been explained on the basis of removal of proton from the free acrylic acid (AA) dopant by the ammonia molecules thereby rendering free conduction sites in the polymer matrix. These results are well supported by FTIR spectral analysis and the X-ray diffraction studies. The FTIR spectra show a remarkable increase in benzenoid and quinoid vibrations. Also, simultaneous appearance of COO− and ammonium ion vibrations is indicative of the interaction of ammonia molecules with acrylic acid. The degree of crystallinity was found to increase substantially upto 58 ppm concentration.

Molecular parameters and their relation to the adhesive performance of acrylic pressure-sensitive adhesives

Abstract: Model acrylic pressure-sensitive adhesives (PSAs) based on poly(2-ethyl-hexyl acrylate-stat-acrylic acid) and poly(n-butyl acrylate-stat-acrylic acid) at 97.5/2.5 wt % were synthesized using semicontinuous emulsion and solution polymerizations. Microgels formed in the lattices retained their discrete network morphology in the film. In contrast, acrylic solution was essentially gel free and crosslinking in the film was provided by the reaction of acrylic acid and post added Al Acetyl Acetonate after solvent evaporation, which led to continuous network morphology. The difference in film network morphology caused significantly lower shear holding power for the film from emulsion PSA compared with that of solvent-borne film. Unlike shear holding power, loop tack and peel of acrylic PSAs were mainly controlled by the same sol/gel molecular parameters, regardless of emulsion or solution PSAs. The important molecular parameters are sol-to-gel ratio, entanglement molecular weight, weight average molecular weight, and to a lesser extent, glass transition temperature. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 79: 2230–2244, 2001

Thin-Film Formation of Calcium Carbonate Crystals: Effects of Functional Groups of Matrix Polymers

Abstract: We report on the preparation of the thin films of calcium carbonate (CaCO3) crystals on solid matrixes, i.e., cellulose, chitosan, and chitin in the presence of an acidic macromolecule. The crystal growth from CaCO3 solution containing poly(acrylic acid) as a soluble acidic polymer results in the formation of CaCO3 thin-film crystals about 0.8 μm in thickness on these solid matrixes. The crystallite size is estimated to be about 30 nm by X-ray measurements and SEM observation. The derivatives of these polysaccharides, whose functional groups of the OH and NH groups are protected, have been prepared and employed as insoluble solid matrixes. No precipitation is observed for the crystallization on the polysaccharide derivatives possessing no proton-donating group even in the presence of poly(acrylic acid). Rhombohedral calcite crystals are obtained from the solution in the absence of the acidic polymer. The infrared spectra for the solid matrixes soaked in the solution show that the acidic polymer is adsorbe...

Plasma‐induced graft polymerization of acrylic acid onto poly(ethylene terephthalate) films

Abstract: The graft polymerization of acrylic acid was carried out onto poly(ethylene terephthalate) films that had been pretreated with argon plasma and subsequently exposed to oxygen to create peroxides. The influence of synthesis conditions, such as plasma treatment time, plasma power, monomer concentration, temperature, and the presence of Mohr's salt, on the degree of grafting was investigated. The observed initial increase in grafting with monomer concentration accelerated at about 20% monomer. The grafting reached a maximum at 40% monomer and subsequently decreased with further increases in monomer concentration. The reaction temperature had a pronounced effect on the degree of grafting. The initial rate of grafting increased with increasing temperature, but the degree of grafting showed a maximum at 50°C. The activation energy of the grafting obtained from an Arrhenius plot was 29.1 kJ/mol. The addition of Mohr's salt to the reaction medium not only led to a homopolymer-free grafting reaction but also diminished the degree of grafting. The degree of grafting increased with increasing plasma power and plasma treatment time. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 81: 2993–3001, 2001

Direct Synthesis of Double Hydrophilic Statistical Di- and Triblock Copolymers Comprised of Acrylamide and Acrylic Acid Units via the MADIX Process

Abstract: Double hydrophilic statistical, diblock and triblock copolymers comprised of acrylamide and acrylic acid units have been synthesized in aqueous medium using the MADIX process. Starting from an either monofunctional or difunctional xanthate, the resulting AB and ABA-type double hydrophilic block copolymers (DHBC) exhibited molar masses predetermined by the initial monomer/xanthate precursor molar ratio and polydispersity indices in the range 1.2–1.5. Batch copolymerizations yielded well-defined statistical copolymers that were chain-extended for the synthesis of novel poly- (acrylic acid-stat-acrylamide)-block-polyacrylamide DHBC.

Surface characterization and antibacterial activity of chitosan-grafted poly(ethylene terephthalate) prepared by plasma glow discharge

Abstract: Poly(ethylene terephthalate) (PET) texture was exposed to oxygen plasma glow discharge to produce peroxides on its surfaces. These peroxides were then used as catalysts for the polymerization of acrylic acid (AA) in order to prepare a PET introduced by a carboxylic acid group (PET-A). Chitosan and quaternized chitosan (QC) were then coupled with the carboxyl groups on the PET-A to obtain chitosan-grafted PET (PET-A-C) and QC-grafted PET (PET-A-QC), respectively. These surface-modified PETs were characterized by attenuated total reflection Fourier transform IR spectroscopy, electron spectroscopy for chemical analysis, and a contact angle goniometer. The amounts of AA, chitosan, and QC grafted on the PET surfaces as determined by the gravimetric method were about 6, 8, and 9 μg/cm2, respectively. The antibacterial activity of the surface-modified PET textures was investigated using a shake flask method. After 6 h of shaking, the growth of bacteria was markedly inhibited by PET with ionically (86% in PET-A−-C+) and covalently (75% in PET-A-C) grafted chitosan and with covalently grafted QC (83% in PET-A-QC). After the laundering the inhibition of the growth of the bacteria was maintained in the range of 48–58%, showing the fastness of the chitosan-grafted PET textures against laundering. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 81: 2769–2778, 2001

Controlling the Permeability of Multilayered Polyelectrolyte Films through Derivatization, Cross-Linking, and Hydrolysis

Abstract: Partial Fischer esterification of poly(acrylic acid) allows tailoring of the hydrophobicity and charge density of multilayered films containing poly(allylamine hydrochloride) (PAH) and derivatized poly(acrylic acid) (d-PAA). As hydrophobicity and charge density strongly affect film permeability, control over these properties is vital for possible applications of PAH/d-PAA films as ion-separation membranes and sensors. The hydrophobicity of these films depends on both the extent of esterification and the nature of the derivatizing alcohol. Even though PAH/d-PAA films are composed of polyelectrolytes, the presence of hydrophobic ester groups results in advancing water contact angles as high as 101°. The hydrophobicity of these coatings allows them to effectively passivate underlying electrodes as shown by minimal peak currents in cyclic voltammograms (CVs) of Ru(NH3)63+ and Fe(CN)63-. Cross-linking of hydrophobic PAH/d-PAA films via heat-induced amidation stabilizes coatings over a wide pH range but does no...

Block copolymers of poly(styrene) and poly(acrylic acid) of various molar masses, topologies, and compositions prepared via controlled/ living radical polymerization. Application as stabilizers in emulsion polymerization

Abstract: A series of well-defined diblock, triblock, and star-block copolymers composed of polystyrene and poly(acrylic acid) were synthesized by controlled/living radical polymerization and used as stabilizers in emulsion polymerization under alkaline conditions. The structure of the copolymers, the size of the blocks, and the composition were varied and their efficiency as stabilizers was correlated with their structural characteristics. The block length was varied from 10 to 30 units for the polystyrene block and from 13 to 266 units for the poly(acrylic acid) block. The copolymers appeared to be efficient stabilizers down to a block copolymer-to-monomer ratio of less than 0.5 wt %. From the comparison of the effect of the different structures and compositions, it was shown that the diblock copolymers were particularly efficient and that the optimal composition was about 10 styrene units and a maximum of 50 acrylic acid units. The triblock and star-block copolymers with external hydrophilic blocks did not behav...

Influence of the COOH and COONa groups and crosslink density of poly(acrylic acid)/ montmorillonite superabsorbent composite on water absorbency

Abstract: A novel poly(acrylic acid)/montmorillonite superabsorbent composite with a water absorbency of 1100 times its own weight was synthesized by the graft copolymerization of acrylic acid with a cross-linking agent in the presence of montmorillonite ultrafine powder. The influence of the amount of crosslinker and montmorillonite on water absorbency has been investigated. It was found that a crosslinker concentration of 0.03 wt% and 30 wt% montmorillonite gave the best results. The collaborative absorbent effect of sodium carboxylate and carboxylic acid groups was superior to that of sodium carboxylate or carboxylic acid groups alone, and the composite with a ratio of about 2/3 for sodium carboxylate to carboxyl acid groups possessed the highest water absorbence. © 2001 Society of Chemical Industry

Influence of Molecular Features on the Tackiness of Acrylic Polymer Melts

Abstract: The effects of molecular weight and acrylic acid content on the adhesive properties of a series of monodisperse poly(n-butyl acrylate) materials have been investigated. The short-time adhesion, or ...

Recent Trends in Hydrogels Based on Starchgraft‐Acrylic Acid: A Review

Abstract: This paper presents a reviewal profile of water absorbing resins based on graft copolymers of acrylic acid and gelatinised starch. It first elaborates on the synthesis of these hydrogels, use of these hydrogels in a variety of commercial applications, and the role of hydrogen bonding in the water absorbing capacity of these hydrogels. It describes the exact experimental conditions for producing hydrogels based on gelatinised maize starch grafted with acrylic acid showing maximum water absorption of 260 g/g.

Aqueous phase size-exclusion-chromatography used for PLP-SEC studies into free-radical propagation rate of acrylic acid in aqueous solution

Abstract: Pulsed laser polymerization (PLP) in conjunction with analysis of the resulting polymer by size-exclusion-chromatography (SEC) was used to measure propagation rate coefficients, kp, of acrylic acid (AA) in aqueous solution at concentrations of 20 and 40 wt % and temperatures between 2.6 and 28.5 °C. Under these conditions, more than 99% of acrylic acid exists in the nonionized form. The molecular weight distribution (MWD) of poly(AA) is directly measured by aqueous SEC. The kp values at 20 wt % are about 60% higher than at 40 wt %. The activation energy of kp is close to 12.0 kJ·mol-1 at both concentrations. At 25 °C and 20 wt %, kp of AA in aqueous solution exceeds 100 000 L·mol-1·s-1 which is the highest kp value determined by the PLP−SEC technique so far.

Catalytic oxidative activation of light alkanes over Mo–V-based oxides having controlled surface

Abstract: An arrangement of catalytically active elements of Mo, V, and Te in an oxide solid with a single crystallographic phase was successfully done by the hydrothermal synthetic method. A black solid powder with a rod-shape (by SEM) was obtained. This catalyst material was first air-treated at 280 °C for 2 h, by which Te was stabilized in the structure. The air-treated sample was then heat-treated at 600 °C in a nitrogen stream. It was revealed by XRD analysis that this treatment made the solid in a well-crystallized state. Finally, in order to break the rods into fine powders, the well-crystallized rod-shaped material was ground, by which a face of the cross-section of the rods seems to be preferentially appeared. Thus obtained catalyst, Mo6V3Te1O x , showed a high activity for the selective oxidation of propane to acrylic acid at 360 °C. Since the grinding was found to be the most effectual determinant in the propane conversion and the acrylic acid formation, the surface on the cross-section part of the rod-shaped crystals is active for the selective oxidation. It was assumed that all the elements of Mo, V, and Te arrange in this surface and effectively promote the consecutive oxidation from propane to acrylic acid via propene and acrolein.

Surface Functionalized Polypropylene: Synthesis, Characterization, and Adhesion Properties

Abstract: Modification of polypropylene by hyperbranched grafting with a poly(acrylic acid) graft was carried out using techniques previously used with gold, aluminum, silicon, and polyethylene surfaces. An initial etching oxidation produced a modified polypropylene that was presumed to contain carboxylic acid functional groups (though none were detected by IR spectroscopy). Then, a series of repetitive grafting experiments using an α,ω-diamine derivative of poly(tert-butyl acrylate) were used to produce surfaces containing significant amounts of poly(acrylic acid). The resulting surfaces were characterized by ATR-IR spectroscopy, contact angle measurements, and XPS spectroscopy. Treatment of the surfaces with alkali produced a more hydrophilic carboxylate surface. Treatment of these surfaces first with ethyl chloroformate followed by pentadecylfluorooctylamine produced a hydrophobic fluorinated surface. Mechanical tests show that such surface modification not only serves as a route to modify polypropylene's hydrop...

Interpenetrating polymer networks based on poly(acrylic acid) and gelatin. I: Swelling and thermal behavior

Abstract: This article describes the synthesis of full and semi-interpenetrating polymer networks (IPNs) based on poly(acrylic acid) and gelatin as polymers 1 and 2, which were crosslinked sequentially using N,N′-methylene bisacrylamide (BAm) and glutaraldehyde, respectively. Various samples were prepared by taking varying amounts of acrylic acid and gelatin in the initial feed. Sequential IPNs were prepared by first polymerizing and crosslinking acrylic acid in the presence of gelatin using redox initiators (ammonium persulphate and sodium metabisulphite) and BAm as a crosslinking agent. Gelatin present in the firm gels was then crosslinked using 4% glutaraldehyde. Characterization of these gels was done by measuring their swelling behavior as a function of pH, temperature, and time. Percent swelling increased with increasing amounts of acrylic acid. The swelling ratio was also determined in the pH range of 1 to 12. Acid/alkali or buffers were used for maintaining pH. A significant increase in the percent swelling was observed when pH of distilled water was above 10. On the other hand, in the case of buffer, the swelling ratio increased with increasing the pH, and a maxima was observed at pH 8.4. A further increase in pH resulted in a decrease in the swelling ratio. Thermal and morphological characterization was done using thermogravimetric analyzer and scanning electron microscopy, respectively. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 82: 217–227, 2001

Palladium Nanoparticle Catalyst Prepared in Poly(Acrylic Acid)-lined Channels of Diblock Copolymer Microspheres

Abstract: Block copolymers self-assemble in bulk, forming a number of intricate block segregation patterns Such assembled structures can serve as precursors to nano- or microstructures with numerous potential applications For many applications, such as catalysis, a high surface area to volume ratio is desirable, which requires “breaking up” copolymer solid into dispersed particles Reported in this letter is the preparation of water-dispersible block copolymer microspheres containing Pd nanoparticles The Pd nanoparticles are a more efficient catalyst for alkene hydrogenation than is the commercial Pd black catalyst