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Query: UMLS:C0267964 (PAA)
 2,561 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Janus nanoparticles have been synthesized consisting of approximately 5 nm magnetite nanoparticles coated on one side with a pH-dependent and temperature-independent polymer (poly(acrylic acid), PAA), and functionalized on the other side by a second (tail) polymer that is either a pH-independent polymer (polystyrene sodium sulfonate, PSSNa) or a temperature-dependent polymer (poly(N-isopropyl acrylamide), PNIPAM). These Janus nanoparticles are dispersed stably as individual particles at high pH values and low temperatures, but can self-assemble at low pH values (PSSNa) or at high temperatures (>31 degrees C) (PNIPAM) to form stable dispersions of clusters of approximately 80-100 nm in hydrodynamic diameter. The Janus nanoparticle compositions were verified using FTIR and XPS, and their structures observed directly by TEM. Their clustering behavior is analyzed by dynamic light scattering and zeta potential measurements.
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PMID:Reversible clustering of pH- and temperature-responsive Janus magnetic nanoparticles. 1920 18

Poly(acrylic acid) (PAA) brushes and poly(methacrylic acid) (PMAA) brushes on gold substrates were synthesized by surface-initiated atom-transfer radical polymerization of sodium acrylate and sodium methacrylate in water media at room temperature. Fourier transform infrared spectroscopy (FTIR) titration and contact angle titration methods were used in combination to investigate the dissociation behavior of these two brushes. Whereas FTIR titration gives effective bulk pKa values of the polyacid brushes (pKabulk of PAA brushes is 6.5-6.6 and pKabulk of PMAA brushes is 6.9-7.0), contact angle titration provides effective surface pKa of the brushes (pKasurf of PAA brushes is 4.4+/-0.01 and pKasurf of PMAA brushes is approximately 4.6+/-0.1). The difference between pKabulk and pKasurf suggests that acid groups further from the substrate surface are easier to ionize and have smaller pKa values. Although such behavior of weak polyelectrolyte brushes has been predicted by theoretical simulation, here we provide the first experimental evidence of this behavior.
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PMID:Dissociation behavior of weak polyelectrolyte brushes on a planar surface. 1924 53

Cationic contact-killing is an important strategy for creating antimicrobial surfaces that prevent viable bacteria attachment. Recent studies have shown that highly swollen, compliant surfaces resist bacterial attachment and a sufficient density of mobile cationic charge can effectively disrupt bacterial cell membranes. Polyelectrolyte multilayers (PEMs), a popular coating system for surface modification, have been used to kill bacteria through the incorporation of contact-killing or leaching biocides. In this work, we show that manipulation of multilayer assembly and postassembly conditions (e.g., pH) to expose mobile cationic charge can create antimicrobial PEMs without the addition of specific biocidal species. As a model system, we explored PEMs comprising poly(allylamine hydrochloride) (PAH) and poly(sodium 4-styrene sulfonate) (SPS) assembled at high pH and subsequently immersed in low pH solutions. This system undergoes a reversible pH-dependent swelling transition, and we demonstrate that antimicrobial functionality at physiological pH conditions can be turned on and off with suitable pH treatment. In both airborne and waterborne bacteria assays, the viability of two strains of Gram positive Staphylococcus epidermidis (S. epidermidis), one biofilm forming and one nonbiofilm forming, and two strains of Gram negative Escherichia coli (E. coli) was effectively reduced on SPS/PAH multilayers displaying accessible cationic charge. To generalize our results, the pH assembly conditions of PEMs comprising poly(acrylic acid) (PAA) and PAH were also modified to introduce antibacterial capabilities.
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PMID:Polyelectrolyte multilayers with intrinsic antimicrobial functionality: the importance of mobile polycations. 1931 89

In this work chitosan membranes modified by contact with poly(acrylic acid) (PAA) aqueous solution at two different temperatures (25 degrees C and 60 degrees C) were obtained. The pure chitosan (CS) membranes, as well as those treated with PAA (CSPAA_25 and CSPAA_60) were characterized by FTIR-ATR, water sorption capacity, thermal analysis (TG/DTG), and scanning electron microscopy (SEM). In addition, in vitro permeation experiments were carried out using metronidazol and sodium sulfamerazine aqueous solutions at 0.1% and 0.2% as model drugs. FTIR-ATR results showed the presence of absorption bands of NH3+ and COO(-) indicating the formation of a polyelectrolyte complex between chitosan and poly(acrylic acid). The results also indicated that PAA penetrates deeper into the membrane at higher temperature (60 degrees C), forming a thicker complex layer. Polyelectrolyte complex formation as well as the influence of treatment temperature was confirmed by lower hydrophilicity, higher thermal stability, and lower permeability of the treated membranes. The results show that the methodology used is a simple and very efficient way to drastically change some membrane properties, especially their permeability.
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PMID:Chitosan membranes modified by contact with poly(acrylic acid). 1955 25

A new concept of designing a photocontrollable supramolecular polymer nanocontainer through the electrostatic association between an azobenzene-containing surfactant (AzoC10) and a double-hydrophilic block ionomer, poly(ethylene glycol)-b-poly(acrylic acid) (PEG(43)-PAA(153)), is described. Such a block ionomer complex can self-assemble in aqueous solution and form vesicle-like aggregates, which are composed of a poly(ethylene glycol) corona and a poly(acrylic acid) shell associated with azobenzene-containing surfactant. The photoisomerization of azobenzene moieties in the block ionomer complex can reversibly tune the amphiphilicity of the surfactants, inducing the disassembly of the vesicles. Such block ionomer complex vesicles are further evaluated as nanocontainers capable to encapsulate and release guest solutes on demand controlled by light irradiation. For example, the vesicles encapsulating the fluorescein sodium display clear spherical images observed by fluorescence microscopy. However, such fluorescence-marked images disappear after releasing the solute from the vesicles triggered by the UV light. Such novel materials are of both basic and practical significance, especially as prospective nanocontainers for cargo delivery.
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PMID:Photocontrolled self-assembly and disassembly of block ionomer complex vesicles: a facile approach toward supramolecular polymer nanocontainers. 1962 65

We report herein the fluorescence response of pyrene in the presence of sodium dodecyl sulfate (SDS) micelle and poly(acrylic acid) (PAA) with Cu(2+) as an ionic quencher. Pyrene present in the PAA-SDS complex is quenched by Cu(2+) at pH approximately 2 ("off" state). Quenched pyrene emission is recovered at pH approximately 8 ("on" state). Due to easy protonation and deprotonation of the PAA chain in aqueous solution, this pH-controlled micellar ternary system exhibits a highly reversible "off-on-off" switch of the pyrene emission.
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PMID:pH-Controlled "off-on-off" switch based on Cu(2+)-mediated pyrene fluorescence in a PAA-SDS micelle aggregated supramolecular system. 1976 33

A series of pH-sensitive composite hydrogel beads, chitosan-g-poly (acrylic acid)/vermiculite/sodium alginate (CTS-g-PAA/VMT/SA), was prepared using CTS-g-PAA/VMT composite and SA by Ca(2+) as the crosslinking agent. The structure and morphologies of the developed composite hydrogel beads were characterized by Fourier transform infrared spectroscopy and scanning electron microscopy. The swelling properties and pH-sensitivity of the beads were investigated. In addition, the drug loading and controlled release behaviors of the beads were also evaluated using diclofenac sodium (DS) as the model drug in stimulated gastric fluids (pH 2.1) and intestinal fluids (pH 6.8). The results indicate that the composite hydrogel beads showed good pH-sensitivity. The release rate of the drug from the composite hydrogel beads is remarkably slowed down, which indicated that incorporating VMT into the composite hydrogel beads can improve the burst release effect of the drug.
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PMID:Preparation and swelling properties of pH-sensitive composite hydrogel beads based on chitosan-g-poly (acrylic acid)/vermiculite and sodium alginate for diclofenac controlled release. 2009 1

This paper deals with bimetallic (Fe/Pd) nanoparticle synthesis inside the membrane pores and application for catalytic dechlorination of toxic organic compounds form aqueous streams. Membranes have been used as platforms for nanoparticle synthesis in order to reduce the agglomeration, encountered in solution phase synthesis which leads to a dramatic loss of reactivity. The membrane support, polyvinylidene fluoride (PVDF) was modified by in situ polymerization of acrylic acid in aqueous phase. Subsequent steps included ion exchange with Fe(2+), reduction to Fe(0) with sodium borohydride and Pd deposition. Various techniques, such as STEM, EDX, FTIR and permeability measurements, were used for membrane characterization and showed that bimetallic (Fe/Pd) nanoparticles with an average size of 20-30 nm have been incorporated inside of the PAA-coated membrane pores. The Fe/Pd-modified membranes showed a high reactivity toward a model compound, 2, 2'-dichlorobyphenyl and a strong dependence of degradation on Pd (hydrogenation catalyst) content. The use of convective flow substantially reduces the degradation time: 43% conversion of dichlorobiphenyl to biphenyl can be achieved in less than 40 s residence time. Another important aspect is the ability to regenerate and reuse the Fe/Pd bimetallic systems by washing with a solution of sodium borohydride, because the iron becomes inactivated (corroded) as the dechlorination reaction proceeds.
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PMID:Aqueous - Phase Synthesis of PAA in PVDF Membrane Pores for Nanoparticle Synthesis and Dichlorobiphenyl Degradation. 2016 75

Conducting polyaniline nanofibers (nf-PANI) were successfully synthesized by simple polymerization of aniline in presence of single and binary dopant agents. Strong hydrochloride acid (HCl), two weak organic acids (poly acrylic acid, PAA, 2-acrylamido-2-methyl-1-propanesulfonic acid, AMPSA) and one anionic surfactant (sodium dodecyl sulfate, SDS) were used to form the binary dopant agents. The binary dopant agent PAA modified the morphology of the single doped PANI, whereas AMPSA and SDS modified the dimensions of the nanofibers: the length size single nanofibers is reduced 1.72 times with binary-doped AMPSA and increased by a factor of 0.7 with SDS. The surface roughness of the films decreases when the dimensions of the nanofibers increase: PANI-SDS film is flatter than PANI-AMPSA film. In general, the conductivity of the single-doped PANI nanofibers (nf-PANI-HCl) was improved by one order of magnitude with binary dopant agents (HCI-PAA, HCl-AMPSA, HCl-SDS). The influence of the binary dopant agents in the nf-PANI-HCl properties is analyzed by Transmission Electron Microscope (TEM), Atomic Force Microscopy (AFM), UV-VIS absorption spectra, thermogravimetric analysis (TGA) and Fourier-Transform infrared spectra (FT-IR).
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PMID:Synthesis of conducting polyaniline nanofibers from single and binary dopant agents. 2035 90

We have fabricated a polymeric superamphiphile based on the electrostatic interaction between the double hydrophilic block copolymer of poly(ethylene glycol)-b-acrylic acid (PEG-b-PAA) and a selenium-containing surfactant (SeQTA). The polymeric superamphiphiles are able to self-assemble to form micelles in solution. The micelles can be disassembled with the addition of 0.1% H(2)O(2) because SeQTA is very sensitive to oxidation. The selenide group in SeQTA is oxidized into selenoxide (SeQTA-Ox) by H(2)O(2), which makes the surfactant more hydrophilic, thus leading to the disassembly of the micelles. In addition, small guest molecules such as fluorescein sodium can be loaded into the micelles made from the polymeric superamphiphiles and released in a controlled way under mild oxidation conditions. This study represents a new way to fabricate stimuli-responsive superamphiphiles for controlled self-assembly and disassembly.
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PMID:Oxidation-responsive micelles based on a selenium-containing polymeric superamphiphile. 2072 31


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