Presence Of PAA Research Articles

Exploring the Origins of Association of Poly(acrylic acid) Polyelectrolyte with Lysozyme in Aqueous Environment through Molecular Simulations and Experiments.

This study provides a detailed picture of how a protein (lysozyme) complexes with a poly(acrylic acid) polyelectrolyte (PAA) in water at the atomic level using a combination of all-atom molecular dynamics simulations and experiments. The effect of PAA and temperature on the protein's structure is explored. The simulations reveal that a lysozyme's structure is relatively stable except from local conformational changes induced by the presence of PAA and temperature increase. The effect of a specific thermal treatment on the complexation process is investigated, revealing both structural and energetic changes. Certain types of secondary structures (i.e., α-helix) are found to undergo a partially irreversible shift upon thermal treatment, which aligns qualitatively with experimental observations. This uncovers the origins of thermally induced aggregation of lysozyme with PAA and points to new PAA/lysozyme bonds that are formed and potentially enhance the stability in the complexes. As the temperature changes, distinct amino acids are found to exhibit the closest proximity to PAA, resulting into different PAA/lysozyme interactions; consequently, a different complexation pathway is followed. Energy calculations reveal the dominant role of electrostatic interactions. This detailed information can be useful for designing new biopolymer/protein materials and understanding protein function under immobilization of polyelectrolytes and upon mild denaturation processes.

Modification of stability properties of yttrium(III) oxide particles by simultaneous adsorption of poly(acrylic acid) and poly(ethylene glycol) for possible applications in wastewater treatment

The adsorption, electrokinetic and stability properties of yttrium(III) oxide—Y2O3 in mixed solutions of macromolecular compounds were investigated. The interfacial behavior of poly(acrylic acid)-PAA and poly(ethylene glycol)—PEG in single and binary systems was examined in the pH range 3–10. The polymers used were characterized by different ionic nature—the PAA is an anionic polymer, whereas PEG belongs to the group of non-ionic polymers. Based on the results obtained, the most probable mechanisms for the binding of PAA and PEG macromolecules on the yttrium(III) oxide surface were proposed. In addition, the analysis of adsorption and electrokinetic data enabled explanation of the obtained changes in the stability of Y2O3 suspensions without and in the presence of PAA or/and PEG, as well as determination of the specific stabilization-destabilization mechanisms of the studied systems. It was shown that yttrium(III) oxide modification by mixed adsorption layers of both polymers with different ionic character changes considerably the surface and stability properties of the examined solid suspensions.Graphical

Low additive peracetic acid enhanced sulfamethazine degradation by permanganate: A mechanistic study

In this study, a novel water treatment process combining permanganate (Mn(VII)) and peracetic acid (PAA, CH3C(O)OOH) was employed to degrade sulfamethazine (SMT), a typical model contaminant. Simultaneous application of Mn(VII) and a small amount of PAA resulted in much faster oxidation of organics than a single oxidant. Interestingly, coexistent acetic acid played a crucial role in SMT degradation, while background hydrogen peroxide (H2O2) had a negligible effect. However, compared with acetic acid, PAA could better improve the oxidation performance of Mn(VII) and accelerate the removal of SMT more significantly. The mechanism of SMT degradation by Mn(VII)-PAA process was systematically evaluated. Firstly, based on the quenching experiments, electron spin resonance (EPR) results and UV–visible spectrum, singlet oxygen (1O2), Mn(III)aq and MnO2 colloids were the predominant active substances, while organic radicals (R-O•) showed negligible contribution. Then, the decay of Mn(VII) in the presence of PAA and H2O2 was investigated. It was found that the coexisting H2O2 accounted for almost all the decay of Mn(VII), PAA and acetic acid both had low reactivity toward Mn(VII). During the degradation process, acetic acid was able to acidify Mn(VII) and simultaneously acted as a ligand to form reactive complexes, while PAA mainly played a role of spontaneously decomposing to produce 1O2, they jointly promoted the mineralization of SMT. Finally, the degradation intermediates of SMT and their toxicities were analyzed. This paper reported the Mn(VII)-PAA water treatment process for the first time, which provided a promising approach for rapid decontamination of refractory organics-polluted water.

Dual driven mechanism (hygro‐redox) semi‐interpenetrating polymer network composite film (polyaniline‐polyacrylic acid/sulfonated poly (ether ether ketone)) for artificial muscles

AbstractDifferent weight ratios of polyaniline (PANI) to poly (acrylic acid) (PAA) were synthesized as interpenetrating polymer networks and blended with sulfonated poly (ether ether ketone) (SPEEK). In‐situ polymerization was performed by chemical oxidation of aniline in the presence of PAA. The composites showed actuation capability in the presence of fuel/air and moisture. Mechanical testing indicated that samples with higher concentration of PAA were stronger. For instance, PANI1PAA2SPEEK3 breaks at 8.4 MPa and has a failure strain of 2.5%, which is higher than PANI3PAA1SPEEK3 at 7 MPa and 2%. However, higher amount of PAA resulted in a lower electrochemical conductivity of 1.52 × 10−2 S/cm for the former and 1.8 × 10−2 S/cm for the latter. Intermolecular interaction at the optimum composition is necessary to induce forward and reverse bending of catalyst coated composite under exposure of fuel and air. In addition, the formation of compact structures and rough surfaces resulted in the maximal contractile strain of 1% for PANI3PAA1SPEEK3 based on moisture actuation.

SURFACE TENSION AND ASSOCIATION IN AQUEOUS SOLUTION SURFACTANTS IN THE PRESENCE OF POLYACRYLAMIDE

The surface tension of aqueous solutions of cationic (dodecylammonium and dodecylpyridinium chlorides) and anionic (sodium dodecylsulfate) surfactants was measured in the presence of polyacrylamide in the solution. A synergistic effect of reducing the surface tension of mixed solutions of cationic surfactants, in the region of sufficiently high concentrations of mixed solutions of sodium dodecyl sulfate, with polyacrylamide in the range of molar ratios of the mixture components - n (Surfactants : PAA) = 1: 1; 1: 0.25 was established. The values ​​of the maximum adsorption, the values ​​of the area per molecule or associate of surfactants in the adsorption layer, as well as the standard Gibbs free energy of adsorption of surfactant - PAA associates are calculated. In accordance with Rosen's model, the composition of mixed adsorption layers at the solution-air interface is calculated, as well as the parameter of intermolecular interaction in adsorption layers between molecules, cationic and anionic ions surfactants and PAA. The values ​​of the critical micelle concentration (CMC) of individual surfactants in aqueous solutions exceed the CMC of the studied surfactants in the presence of PAA, which promotes micelle formation.

Stabilization of Calcium Oxalate Precursors during the Pre- and Post-Nucleation Stages with Poly(acrylic acid).

In this work, calcium oxalate (CaOx) precursors were stabilized by poly(acrylic acid) (PAA) as an additive under in vitro crystallization assays involving the formation of pre-nucleation clusters of CaOx via a non-classical crystallization (NCC) pathway. The in vitro crystallization of CaOx was carried out in the presence of 10, 50 and 100 mg/L PAA by using automatic calcium potentiometric titration experiments at a constant pH of 6.7 at 20 °C. The results confirmed the successful stabilization of amorphous calcium oxalate II and III (ACOII and ACO III) nanoparticles formed after PNC in the presence of PAA and suggest the participation and stabilization of polymer-induced liquid-precursor (PILP) in the presence of PAA. We demonstrated that PAA stabilizes CaOx precursors with size in the range of 20–400 nm. PAA additive plays a key role in the in vitro crystallization of CaOx stabilizing multi-ion complexes in the pre-nucleation stage, thereby delaying the nucleation of ACO nanoparticles. Indeed, PAA additive favors the formation of more hydrated and soluble phase of ACO nanoparticles that are bound by electrostatic interactions to carboxylic acid groups of PAA during the post-nucleation stage. These findings may help to a better understanding of the pathological mineralization resulting in urolithiasis in mammals.

The Probable Mechanism for Silicon Capture by Diatom Algae: Assimilation of Polycarbonic Acids with Diatoms-Is Endocytosis a Key Stage in Building of Siliceous Frustules?

Many organisms including unicellular (diatoms, radiolaria, and chrysophytes), higher plants (rice and horsetail) and animals (sponges) use silica as a main part of skeletons. The bioavailable form of silicon is silicic acid and the mechanism of silicic acid penetration into living cells is still an enigma. Macropinocytosis was assumed as a key stage of the silicon capture by diatoms but assimilation of monomeric silicic acid by this way requires enormous amounts of water to be passed through the cell. We hypothesized that silicon can be captured by diatoms via endocytosis in the form of partially condensed silicic acid (oligosilicates) whose formation on the diatom surface was supposed. Oligosilicates are negatively charged nanoparticles and similar to coils of poly(acrylic acid) (PAA). We have synthesized fluorescent tagged PAA as well as several neutral and positively charged polymers. Cultivation of the diatom Ulnaria ferefusiformis in the presence of these polymers showed that only PAA is able to penetrate into siliceous frustules. The presence of PAA in the frustules was confirmed with chromatography and PAA causes various aberrations of the valve morphology. Growth of U. ferefusiformis and two other diatoms in the presence of tri- and tetracarbonic fluorescent tagged acids points to the ability of diatoms to recognize substances that bear four acidic groups and to include them into siliceous frustules. Thus, partial condensation of silicic acid is a plausible first stage of silicon assimilation.

Electrochemical nucleic acid hybridization biosensor based on poly(L-Aspartic acid)-modified electrode for the detection of short oligonucleotide sequences related to hepatitis C virus 1a

This work describes, for the first time, the fabrication of poly(L-aspartic acid) (PAA) film modified pencil graphite electrode (PGE) for the detection of hepatitis C Virus 1a (HCV1a). The presence of PAA on the electrode surface can provide free carboxyl groups for covalent binding of biomolecules. The PGE surface was first coated with PAA via electropolymerization of the L-aspartic acid, and avidin was subsequently attached to the PAA modified electrode by covalent attachment. Biotinylated HCV1a probes were immobilized on avidin/PAA/PGE via avidin-biotin interaction. The morphology of PAA/PGE was examined using a scanning electron microscope. The hybridization events were monitored with square wave voltammetry using Meldola’s blue (MDB). Compared to non-complementary oligonucleotide sequences, when hybridization was carried out between the probe and its synthetic targets or the synthetic polymerase chain reaction analog of HCV1a, the highest MDB signal was observed. The linear range of the biosensor was 12.5 to 100 nM and limit of detection was calculated as 8.7 nM. The biosensor exhibited favorable stability over relatively long-term storage. All these results suggest that PAA-modified electrode can be used to nucleic acid biosensor application and electropolymerization of L-aspartic acid can be considered as a good candidate for the immobilization of biomolecules.

Electrohydrodynamic jet 3D-printed PCL/PAA conductive scaffolds with tunable biodegradability as nerve guide conduits (NGCs) for peripheral nerve injury repair

NGCs are considered as an alternative treatment method for treating peripheral nerve injuries in place of nerve autografts. Biomimicry, conductivity, and biodegradability are the properties expected of an ideal NGC. PCL/PAA NGCs with three different concentrations of PAA (2.5, 5 and 7.5%) were fabricated using EHD-jet 3D printing. The mechanical properties of the PCL/PAA NGCs mimic the native human nerve properties (ultimate tensile strength of 6.5 to 11.7 MPa) and the conductivity match that of the amphibian motor nerve fiber myelin sheath (10−6 S/cm). The in vitro degradation studies reveal that they are biodegradable and injury/site-specific biodegradability can be obtained by tuning the PCL/PAA concentration ratio. In addition, PAA being a polyanionic polymer has the potential to act as a cation-exchanger, mimicking the functions of the nerve cortical gel layer, thereby influencing the electrophysiological phenomena called nerve excitation and conduction. Neural differentiation studies with PC12 cells assessed by the Reverse Transcription-Polymerase Chain Reaction (RT-PCR) and immunocytochemistry showed enhanced gene expression with the presence of PAA. Our results suggest that the EHD-jet 3D printed porous conductive PCL/PAA NGCs has the potential to be used in the treatment of peripheral nerve injuries.

Anionic polyelectrolytes in titanosilicate molecular sieve synthesis towards simultaneously accomplishing low production cost and high catalytic activity.

Assisted by an anionic polyelectrolyte of poly(acrylic acid) (PAA), high-performance titanium silicalite-1 (TS-1) could be facilely synthesized at very low usage of expensive organic templates (tetrapropylammonium hydroxide). The presence of PAA helped to incorporate more active Ti species into the TS-1 framework and change the morphology to a plate-like shape, which was beneficial to molecular diffusion among its micropores to access the Ti active sites. Therefore, TS-1 synthesized with PAA showed much higher catalytic activity than that synthesized using the traditional synthesis without polyelectrolytes, and only a 30% usage amount of organic template was used. Moreover, this ultra-cheap catalyst also displayed a better catalytic activity than commercial TS-1 synthesized via a series of complicated preparation processes including alkene epoxidation with hydrogen peroxide as a green oxidant.

Exploring the effect of poly(acrylic acid) on pre- and post-nucleation BaSO4species: new insights into the mechanisms of crystallization control by polyelectrolytes

Barium sulphate (BaSO4) precipitation has been suggested to occur by non-classical pathways that include the formation of a dense liquid precursor phase, nucleation of primary nanoparticles and two levels of oriented aggregation resulting in micron-sized barite single crystals. In this study we build from this previous knowledge and explore how Ba2+ and SO42− ions associate in solution prior to nucleation of a solid phase and the effects of poly(acrylic acid) (PAA) in these pre-nucleation and post-nucleation stages. With this aim, in situ potentiometric experiments and transmission electron microscopy (TEM) observations of time-resolved quenched samples were carried out. Additional bulk precipitation experiments in which supersaturation was achieved by rapid mixing of Ba- and SO4-bearing solutions were performed. The resultant precipitates were characterized by scanning electron microscopy (FESEM and ESEM), transmission electron microscopy (TEM), X-ray diffraction (XRD) and thermogravimetric (TG) analyses. Our study provides evidence that barium sulphate precipitation occurs via the formation of ion associates in solution (ion pairs and/or clusters), that are significantly destabilized in the presence of PAA. This is associated with a noticeable delay in nucleation in the presence of PAA. Thus, our results provide indirect evidence that suggests that prenucleation ion associates must form prior to solid BaSO4 nucleation. Alternatively, BaSO4 mineralization in the presence of PAA seems to occur by a different route that consists in the formation of Ba-PAA globules in solution followed by an amorphous hydrated BaSO4 phase that transform into crystalline barite nanoparticles. PAA seems to stabilize this amorphous phase, which nevertheless also forms in the absence of PAA. Finally, single micron-sized crystals are formed by the oriented attachment of distinguishable smaller subunits, thus forming mesocrystals in the presence and absence of PAA.

The influence of poly(acrylic acid) on micellization and gelation characteristics of aqueous Pluronic F127 copolymer system

The influence of anionic homopolymer poly(acrylic acid) (PAA) of low (1800 g/mol) and high (450,000 g/mol) molecular weights on the micellization and gelation characteristics of aqueous Pluronic F127 (EO97PO69EO97) triblock copolymer (with EO = ethylene oxide and PO = propylene oxide) was studied using differential scanning calorimetry, dynamic light scattering, spectrophotometry, tube inversion technique, and rheometry. It is found that the addition of PAA decreases the critical micellization temperature (CMT) of F127 due to their association via hydrogen bonding. This association becomes stronger at temperatures ≥CMT, arising from the increased affinity between the PO units and PAA. F127-PAA complexation results in lesser PO dehydration and smaller micellization enthalpy (∆H). With increasing PAA concentration, this effect becomes stronger and more F127 bound on PAA is present in the sample, eventually leading to vanishing ΔH. In the presence of PAA, gel region of F127 decreases with increasing PAA concentration due to the order disrupting effect of PAA on the arrangement of packed micelles. Both the micellization and gelation processes of F127 in the presence of PAA are thermoreversible. The PAA effects on both processes become considerably weak at high pH.

A Facile Route Towards the Synthesis of Nanocomposites for the Application as Solid Electrolytes via Grafting Polymer from TiO2 Nanoparticles

Poly(acrylic acid)/TiO2 (PAA-g-TiO2) nanocomposites were synthesized by the surface thiol-lactam initiated radical polymerization (TLIRP) technique. The synthetic strategy involved the modification of TiO2by a one-step direct anchoring of thiol groups via reaction between the hydroxyl groups on the surface of TiO2 and triethoxysilane groups of (3-mercapto)propyltrimethoxysilane (MPTMS). The modified TiO2nanoparticles (NPs) were dispersed in acrylic acid monomers and subsequently polymerized by TLIRP to yield PAA-g-TiO2nanocomposites. FT-IR spectra, XPS, EDS, UV-Vis spectroscopy and SEM images provided direct and clear evidence for the coordination of MPTMS and the presence of PAA on TiO2 NPs. The immobilization of PAA onto TiO2 NPs significantly improved their dispersibility in organic solvents. Additionally, laser diffraction spectroscopy of the TiO2 NPs was examined in order to get the size distribution of nanocomposites.

An Experimental Study of Stabilization of Trivalent Thallium by Natural Organic Matter

Abstract Stabilization of dissolved trivalent thallium, Tl(III), in water by complexation with humic acid and its analogue (poly(acrylic acid), PAA) was studied. Chromatographic analysis showed that Tl(III) was stabilized by the complexation, which allowed us to estimate the stability constant of Tl(III)–humate complex. Cyclic voltammograms of Tl showed that the redox potential of Tl(III)/Tl(I) redox couple in the presence of PAA was lower than that without PAA. These results suggest that Tl(III) can be present in natural water by the stabilization of Tl(III) rather than Tl(I) due to the formation of humate complex.

Uniform Poly(acrylic acid)‐Functionalized Lanthanide‐Doped LaVO4 Nanophosphors with High Colloidal Stability and Biocompatibility

AbstractLn‐doped (Ln = Eu or Nd) LaVO4 nanoparticles functionalized with poly(acrylic acid) (PAA) were prepared from lanthanide and vanadate precursors in the presence of PAA by a simple one‐pot method that consists of a homogeneous precipitation reaction in ethylene glycol/water at a moderate temperature (120 °C). The size of the nanoparticles could be modified in the 40–70 nm range by adjusting the amount of PAA added. The effects of the Eu and Nd contents of these nanomaterials on theirs optical properties (emission intensity and lifetime) were also analyzed to find the optimum nanophosphors. Finally, the nanoparticles showed negligible cytotoxicity for Vero cells at concentrations up to 0.05 mg mL–1 and a high colloidal stability in physiological buffer solutions; therefore, they satisfy the most important requirements for in vitro biotechnological applications.

Inhibition of Homogeneous Formation of Magnesium Hydroxide by Low-Molar-Mass Poly(acrylic acid) with Different End-Groups

The homogeneous crystallization of magnesium hydroxide (Mg(OH)2) was carried out at 97 °C in the absence and presence of low molar mass (Mn ≤ 2000) poly(acrylic acid) (PAA) terminated with different end groups. A significant decrease in Mg(OH)2 crystal growth was found in the presence of PAA, with relatively hydrophobic end-groups being most effective. The end-groups that were most effective were decyl isobutyrate which are more hydrophobic than the hexyl isobutyrate end-groups previously shown to be maximally effective in inhibiting calcium carbonate and calcium oxalate scaling.

Micro/nanostructures of PANI obtained in the presence of water soluble polymers and their electrochemical sensing properties

Polyaniline (PANI) micro/nanostructures are synthesized by electrochemical polymerization, and characterized by field-emission scanning electron microscopy, Fourier transform infrared spectroscopy and UV-visible spectroscopy. It is revealed that the PANI microwires are produced with high yield with diameters of about 2 μm and lengths of several hundreds of micrometers, while nanostructures in the presence of PAA have diameters of about 500 nm. The micro/nanostructured PANI films are very stable and show high electrocatalytic reduction toward H2O2, which makes it an ideal substrate for H2O2 detection and offers great promise for biosensing applications.

Comparing the spectral properties of pyrene as free molecule, label and derivative in some colloidal systems

This paper investigates the behavior of pyrene as free molecule (probe), label and derivative in some colloidal systems. Aqueous octaethylene glycol mono n-dodecyl ether (C12E8) with or without poly(acrylic acid) (PAA), and a hydrophobically modified polyacrylate are considered. The effect of C12E8 on PAA labeled with pyrene is also studied. As a probe, pyrene has a typical behavior in the absence or presence of PAA. The labeled PAA has the peak corresponding to the sandwich excimer even in the absence of surfactant. The pyrene derivative is 4-(N′,N′-diphenyl-hydrazine)-3,5-dinitrobenzoic acid 2-oxo-2-pyren-2-yl-ethyl ester. Its fluorescence emission is low and bathochromically shifted by 9nm with respect to pyrene. The low fluorescence emission of derivative is due to its self-quenching. The data reveal that pyrene probe is located in the free or polymer-bound micelles. The labels on PAA create hydrophobic domains and shrink the polymer coil. By surfactant addition, labeled pyrene is solubilized in micelles palisade layer, closer to the ethylene oxide (EO) chains. The derivative is also located into the micellar palisade layer, in the proximity of the EO groups. The fluorophore behavior is discussed in relation to the critical points of surfactant and polymer–surfactant systems.

Inhibition of homogenous formation of calcium carbonate by poly (acrylic acid). The effect of molar mass and end-group functionality

The ability of poly(acrylic acid) (PAA) with different end groups and molar masses prepared by Atom Transfer Radical Polymerization (ATRP) to inhibit the formation of calcium carbonate scale at low and elevated temperatures was investigated. Inhibition of CaCO3 deposition was affected by the hydrophobicity of the end groups of PAA, with the greatest inhibition seen for PAA with hydrophobic end groups of moderate size (6–10 carbons). The morphologies of CaCO3 crystals were significantly distorted in the presence of these PAAs. The smallest morphological change was in the presence of PAA with long hydrophobic end groups (16 carbons) and the relative inhibition observed for all species were in the same order at 30°C and 100°C. As well as distorting morphologies, the scale inhibitors appeared to stabilize the less thermodynamically favorable polymorph, vaterite, to a degree proportional to their ability to inhibit precipitation.

Interactions of silica nanoparticles with poly(ethylene oxide) and poly(acrylic acid): Effect of the polymer molecular weight and of the surface charge

The properties and the structure of polymer-modified silica nanoparticles were investigated by several characterization methods, with an emphasis on scattering techniques. Both bare and amino functionalized nanoparticles were used. To determine the effect of the charge, the polymer used was either nonionic poly(ethylene oxide) (PEO) or partially deprotonated poly(acrylic acid) (PAA). The particles coated with PEO were investigated by small-angle neutron scattering using the method of external contrast variation to observe the polymer coverage. The quantity adsorbed was found to be increasing with the molecular weight, and the surface type, bare or aminated, did not have a significant influence on the quantity adsorbed. The adsorption of PAA on positively charged aminated particles was investigated by dynamic light scattering and zeta potential measurements. A charge reversal, from positive to negative, was induced by the presence of PAA. Through the derivation of the structure factor, small-angle X-ray scattering provided significant information on the formation of aggregates at low PAA concentrations.