Increasing PAA Content Research Articles

Linking polymer hydrophobicity and molecular interactions to rheology and tribology in phospholipid-containing complex gels

HypothesisThe rheological behavior and frictional properties (macroscopic level) of systems containing a hydrophobically modified polymer and phospholipids depend on the hydrophobic association that occur between the hydrophobic moiety of the polymer and the phospholipid tails (molecular level). The hydrophobicity of the polymer can thus be used to control its interactions with phospholipids, and manipulate complex gel macroscopic behavior. ExperimentsBy using systems composed of a crosslinked hydrophobically modified polyacrylic acid (HMPAA) or a crosslinked polyacrylic acid polymer (PAA) and phospholipids, we examine the underlying mechanisms through which the components interact using isothermal titration calorimetry (ITC) and their effect on rheological and tribological characteristics of complex gels. FindingsWe find the systems containing HMPAA and phospholipid exhibit gel-like behavior with the elastic modulus increasing substantially upon phospholipid addition due to hydrophobic interactions that result in a more interconnected network formation, as evidenced by ITC measurements. Similar experiments with a crosslinked polyacrylic acid polymer (PAA) show no interactions, lending credence to our hypothesis. In addition, soft tribological behavior shows lower friction coefficients at low entrainment speeds with HMPAA concentration and the addition of phospholipid, while no change in friction coefficient was observed in the case of increasing PAA concentration, indicating HMPAA and phospholipids to be interacting with the soft PDMS contacts.

Effects of Molecular Weight and Concentration of Poly(Acrylic Acid) on Biomimetic Mineralization of Collagen

Inspired by nature, poly(acrylic acid) (PAA) and other polyelectrolytes have been used as noncollagenous proteins (NCPs) surrogates for biomimetic intrafibrillar mineralization of collagen fibrils and thus, to model the ultrastructure of bone, to study the mechanism of bone mineralization and, more scarcely to fabricate scaffolds for hard tissue engineering. The objective of this study was to systematically investigate the effect of the molecular weight (MW) and the concentration of PAA on the rate and pattern of biomineralization of collagen matrices. Densified type I collagen films were mineralized in supersaturated PAA-stabilized amorphous calcium-phosphate (PAA-ACP) solutions containing increasing MW (2 kDa, 50 kDA, 450 kDa) and concentrations (10, 25, 50 mg/L) of PAA up to 7 days. The stability and physical properties of collagen-free PAA-ACP solutions were also investigated. In our system, lowering PAA MW and increasing PAA concentration resulted in solutions with increasing stability. Over stable PAA-ACP solutions that fully inhibited mineralization of the collagen matrices were achieved using PAA 2k-50. Conversely, unstable solutions were obtained using high PAA MW at low concentrations. Nucleation and growth of significant amount of extrafibrillar minerals on the collagen fibrils was obtained using these solutions. In a wide range of combined MW and concentration of PAA we obtained intrafibrillar mineralization of collagen with hydroxyapatite crystals aligned parallel to the collagen fibril as in natural tissues. Intrafibrillar mineralization was correlated with PAA-ACP stability and growth of the PAA-ACP particles in solution. Our results support using PAA to surrogate NCPs function as selective inhibitors or promoters of biological mineralization and provide parameters to manufacture new biomimetic scaffolds and constructs for bone and dentin tissue engineering.

Controllable synthesis of poly(acrylic acid)-stabilized nano-hydroxyapatite suspension by an ultrasound-assisted precipitation method

An improved precipitation method was developed to prepare stable nano-hydroxyapatite (HAP) suspension with the aid of steric effect of poly(acrylic acid) (PAA) and acoustic cavitation effect. The effects of reaction temperature and PAA concentration on the formation of nano-HAP suspension were studied. The rising temperature led to the transformation of spherical amorphous calcium phosphate (ACP) to needle-like nano-HAP crystals with the increase in size. The increasing PAA concentration mightily hindered the crystallization of HAP instead of decreasing the size. PAA provided steric effect to stabilize nano-HAP in solution due to the electrostatic interaction between –COO- of PAA and Ca2+ on the surface of HAP. The obtained PAA-stabilized nano-HAP suspension showed good stability in different media (water, PBS, RPMI 1640) and noncytotoxicity. This study provides a potential technology for the controllable synthesis of stable nano-HAP suspension.

Enhanced oxygen-barrier and water-resistance properties of poly(vinyl alcohol) blended with poly(acrylic acid) for packaging applications

To enhance the oxygen-barrier and water-resistance properties of poly(vinyl alcohol) (PVA) and expand its food packaging applicability, five crosslinked poly(vinyl alcohol)/poly(acrylic acid) (PVA/PAA) blend films were prepared via esterification reactions between hydroxyl groups in PVA and carboxylic acid groups in PAA. The physical characteristics of the blends, including the thermal, barrier, mechanical and optical properties, were investigated as a function of PAA ratio. With increasing PAA content, the crosslinking density was significantly increased, resulting in changes in the chemical structure, morphology and crystallinity of the films. The oxygen transmission rate of pure PVA decreased from 5.91 to 1.59 cc m−1 day−1 with increasing PAA ratio. The water resistance, too, increased remarkably. All the blend films showed good optical transparency. The physical properties of the blend films were strongly correlated with the chemical structure and morphology changes, which varied with the PAA content. © 2016 Society of Chemical Industry

Phase separation and permeability in polyisobutylene-based miktoarm star polymers

The phase behavior of (PS-PIB)2-s-PAA miktoarm star terpolymers with varying volume fractions of PAA was investigated directly by transmission electron microscopy, atomic force microscopy, and small-angle X-ray scattering, and indirectly by thermogravimetric analysis and degree of water sorption. The microdomains of (PS-PIB)2-s-PAA demonstrate a unique and unexpected progression from highly ordered cylinders, to lower ordered spheres, to gyroid structures with increasing PAA content from 6.6 to 47 wt %. Interestingly, the phase behavior in the miktoarm star polymer system is significantly different from that reported previously for the linear counterpart of similar composition (PAA-PS-PIB-PS-PAA), where a steady progression from cylindrical to lamellar morphology was observed with increasing PAA content. At low PAA concentrations, the morphology is driven primarily by the relative solubility of the components, while at high PAA content the molecular architecture dominates. Thermal annealing demonstrated the thermodynamic stability of the morphologies, indicating the potential for design of novel microstructures for specific applications through precise control of architecture, composition, and interaction parameters of the components. © 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2016, 54, 916–925

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.

Facile electrospun Polyacrylonitrile/poly(acrylic acid) nanofibrous membranes for high efficiency particulate air filtration

Polyacrylonitrile/poly(acrylic acid) (PAN/PAA with weight radios of 3/7, 4/6, 5/5, 6/4, 7/3 and 10/0) nanofibers (NFs) were prepared as filter medium by electrospinning. The tensile strength of blended nanofibrous mats increased as increasing PAA content, from 3.8 to 6.6 MPa, higher than pristine PAN. The mesoporous effect of nanofibrous mats was also investigated from the nitrogen physisorption isotherms, average pore size in the range of 17–44 nm. Air filtration efficiency and pressure drop of nanofibrous mats were evaluated. PAN/PAA (6/4) NFs showed high filtration efficiency (99.994 %) with lowest pressure drop (160 Pa) for 300–500 nm sodium chloride aerosol particles at a 5.3 cm/s airflow velocity, which suggested this material was appropriate as a promising candidate for high performance filters.

Polyaniline/poly(acrylic acid) composite film: A promising material for enzyme-aided electrochemical sensors

Conducting films composed of polyaniline (PANI) and poly(acrylic acid) (PAA) were prepared by electrochemical polymerization of aniline in the presence of various concentrations of PAA. The conductivity of the composite films (PANI/PAA films) was determined by in-situ measurement in a phosphate buffer solution of pH 7.0 and corroborated by electrochemical impedance spectroscopy. In the range of PAA content up to 18.2 %, the conductivity of the PANI/PAA film was found to increase significantly with increasing PAA content, owing to enhanced protonation of nitrogen atoms of PANI. Glucose oxidase (GOx) was immobilized on the PANI/PAA films by the condensation reaction with the carboxyl groups of PAA on their surfaces. Amperometric sensing was carried out for glucose by use of the GOx-immobilized PANI/PAA film as an enzyme electrode. The GOx-immobilized film gave the current response to glucose depending on its concentration. Although the current response leveled off to reach a constant value in a high glucose concentration range, the value was found to increase with increasing PAA content in the PANI/PAA film used, corresponding to the increased conductivity of the film.

Calcium sulfate dihydrate (gypsum) scale inhibition by PAA, PAPEMP, and PAA/PAPEMP blend

The effects of poly(acrylic acid), PAA, polyamino polyether methylene phosphonic acid, PAPEMP, and PAA / PAPEMP blend on calcium sulfate dihydrate (gypsum) are reported in this paper. It has been found that gypsum inhibition by PAA increases with increasing PAA concentration. Among the various phoshonates (i.e., aminotris(methylene phosphonic acid), AMP; hydroxyphosphono acetic acid, HPA; hydroxyethylidene 1,1-diphosphonic acid, HEDP; 2-phosphonobutane 1,2,4-tricarboxylic acid, PBTC; and polyether polyamino phosphonic acid, PAPEP) evaluated, PAPEMP shows the best inhibition for gypsum precipitation. It has also been observed that presence of PAPEMP exhibits synergistic effect on the performance of PAA. Results on calcium ion compatibility of various phosphonates show that PAPEMP compared to other phosphonates tested show higher tolerance to calcium ions.

Pervaporative separation of isopropyl alcohol/water mixtures: effects of the operation conditions

Abstract Isopropyl alcohol/water mixture was separated by an environmentally friendly membrane process: pervaporation. Pervaporation experiments were carried out with a polymer blend membranes of poly(vinyl alcohol) (PVA) and poly(acrylic acid) (PAA) at different temperatures. PVA/PAA cross-linked membranes were prepared with different blend ratios. The influence of PVA/PAA ratio and of liquid mixture composition were investigated. The apparent activation energies were calculated at different temperatures. With increasing PAA content in the membranes fluxes decreased and selectivities increased. The flux increased with increasing operation temperature, as selectivity decreased. The studies showed that isopropylalcohol/water mixtures can be separated by pervaporation which is an energy efficient technology using the prepared membranes.

The role of hydrogen-bonding interaction in poly(vinyl alcohol)/poly(acrylic acid) blending solutions and their films

The aim of this work is to investigate the hydrogen-bonding interaction in poly(vinyl alcohol) (PVA)/poly(acrylic acid) (PAA) blending system and its influence on rheological properties in solution and the physical properties in solid state. Introducing PAA into PVA solutions resulted in a thickening behavior of blend solutions. The viscosity of the solutions increased with PAA content increasing, and a maximum viscosity could be obtained when the ratio of PVA/PAA was 70/30. The intermolecular hydrogen-bonding and miscibility between PVA and PAA in solid state were investigated by differential scanning calorimetry (DSC), Fourier transform infrared spectroscopy (FTIR) and mechanical measurements. The results displayed the great influence of introducing PAA on the properties of blending films. The tensile strength increased from 89.31 MPa to 119.8 MPa and Young’s modulus improved by over 300% with increasing PAA concentration compared with those of pure PVA films. By systematically studying the rheological behaviors of solutions and the physical properties of films, the influence of hydrogen-bonding in solutions and solid states were discussed.

Moisture‐activated rheological structuring of nonaqueous poloxamine–poly(acrylic acid) systems designed as novel biomedical implants

This study reports the formulation/characterisation of novel polymeric platforms designed to behave as low‐viscosity systems in the nonaqueous state, however, following uptake of aqueous fluids, exhibit rheological structuring and mucoadhesion. The rheological/mechanical and mucoadhesive properties of platforms containing poly(acrylic acid) (PAA, 1%, 3%, 5%, w/w) and poloxamines (Tetronic 904, 901, 704, 701, 304), both in the absence and presence of phosphate buffered saline (PBS, pH 7.4) are described. With the exception of Tetronic 904, all formulations exhibited Newtonian flow in the nonaqueous state, whereas, all aqueous formulations displayed pseudoplastic flow. The consistency and viscoelastic properties were dependent on the concentrations of PAA and PBS and Tetronic grade. PBS significantly increased the consistency, viscoelasticity and mucoadhesion, reaching a maximum at a defined concentration of PBS that was dependent on PAA concentration and Tetronic grade. Formulations containing Tetronic 904 exhibited greatest consistency and elasticity both prior to and after dilution with PBS. Increasing PAA concentration enhanced the mucoadhesive properties. Prolonged drug release of metronidazole was observed from formulations containing 10% (w/w) PBS, 3% and, particularly, 5% (w/w) PAA. It is suggested that the physicochemical properties of formulations containing 3% or 5% (w/w) PAA and Tetronic 904, would render them suitable platforms for administration to body cavities. © 2009 Wiley‐Liss, Inc. and the American Pharmacists Association J Pharm Sci 99: 1838–1854, 2010

Self‐assembled complexes of poly(acrylic acid) and poly(styrene)‐block‐poly(4‐vinyl pyridine)

AbstractPolymer complexes were prepared from high molecular weight poly(acrylic acid) (PAA) and poly(styrene)‐block‐poly(4‐vinyl pyridine) (PS‐b‐P4VP) in dimethyl formamide (DMF). The hydrogen bonding interactions, phase behavior, and morphology of the complexes were investigated using Fourier transform infrared (FTIR) spectroscopy, differential scanning calorimetry (DSC), dynamic light scattering (DLS), atomic force microscopy (AFM), and transmission electron microscopy (TEM). In this A‐b‐B/C type block copolymer/homopolymer system, P4VP block of the block copolymer has strong intermolecular interaction with PAA which led to the formation of nanostructured micelles at various PAA concentrations. The pure PS‐b‐P4VP block copolymer showed a cylindrical rodlike morphology. Spherical micelles were observed in the complexes and the size of the micelles increased with increasing PAA concentration. The micelles are composed of hydrogen‐bonded PAA/P4VP core and non‐bonded PS corona. Finally, a model was proposed to explain the microphase morphology of complex based on the experimental results obtained. The selective swelling of the PS‐b‐P4VP block copolymer by PAA resulted in the formation of different micelles. © 2009 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 47: 1192–1202, 2009

Nanostructure and hydrogen bonding in interpolyelectrolyte complexes of poly(ɛ-caprolactone)-block-poly(2-vinyl pyridine) and poly(acrylic acid)

Nanostructured poly(ɛ-caprolactone)-block-poly(2-vinyl pyridine) (PCL-b-P2VP)/poly(acrylic acid) (PAA) interpolyelectrolyte complexes (IPECs) were prepared by casting from THF/ethanol solution. The morphological behaviour of this amphiphilic block copolymer/polyelectrolyte complexes with respect to the composition was investigated in a solvent mixture. The phase behaviour, specific interactions and morphology were investigated using differential scanning calorimetry (DSC), Fourier transform infrared (FTIR) spectroscopy, optical microscopy (OM), dynamic light scattering (DLS) and atomic force microscopy (AFM). Micelle formation occurred due to the aggregation of hydrogen bonded P2VP block and polyelectrolyte (PAA) from non-interacted PCL blocks. It was observed that the hydrodynamic diameter (Dh) of the micelles in solution decreased with increasing PAA content up to 40wt%. After 50wt% PAA content, Dh again increased. The micelle formation in PCL-b-P2VP/PAA IPECs was due to the strong intermolecular hydrogen bonding between PAA homopolymer units and P2VP blocks of the block copolymer. The penetration of PAA homopolymers into the shell of the PCL-b-P2VP block copolymer micelles resulted in the folding of the P2VP chains, which in turn reduced the hydrodynamic size of the micelles. After the saturation of the shell with PAA homopolymers, the size of the micelles increased due to the absorption of added PAA onto the surface of the micelles.

Swelling behavior and drug release of poly(vinyl alcohol) hydrogel cross-linked with poly(acrylic acid)

Thermal cross-linking method of poly(vinyl alcohol) (PVA) using poly(acrylic acid) (PAA) was carried out on PVA/PAA hydrogels. The level of gelation was measured in the PVA/ PAA hydrogels with various PAA contents. The swelling behavior at various pHs showed that the swelling kinetics and water contents of the PVA/ PAA hydrogels reached equilibrium after 30 h, and the time to reach the equilibrium state decreased with increasing PAA content in the hydrogel. The water content increased with increasing pH of the buffer solution. The permeation and release of the drug were tested using indomethacin as a model drug. The permeated and released amounts of the drug increased with decreasing the PAA content because of the low free volume in the hydrogel due to the higher cross-linking density. The kinetic profile of drug release at various pHs showed that all samples reached the equilibrium state within the 5 h.

Preparation and characterization of interpenetration polymer network films based on poly(vinyl alcohol) and poly(acrylic acid) for drug delivery

AbstractA series of full interpenetrating polymer network (full‐IPN) films of poly(acrylic acid) (PAA)/poly (vinyl alcohol) (PVA) were prepared by radical solution polymerization and sequential IPN technology. Attenuated total reflectance‐Fourier transform infrared spectroscopy, swelling properties, mechanical properties, morphology, and glass transition temperature of the films were investigated. FTIR spectra analysis showed that new interaction hydrogen bonds between PVA and PAA were formed. Swelling property of the films in distilled water and different pH buffer solution was studied. Swelling ratio increased with increasing PAA content of IPN films in all media, and swelling ratio decreased with increasing PVA crosslink degree. Tensile strength and elongation at break related not only to the constitution of IPNs but also to the swelling ratio of IPNs. Mechanical property of glutaraldehyde (0.5%) for poly(vinyl alcohol) crosslinking was better than that of glutaraldehyde (1.0%). DSC of the IPN films showed only a single glass transition temperature (Tg) for each sample, and Tg data showed a linear relationship with network composition. Morphology was observed a homogeneous structure, indicating the good compatibility and miscibility between PAA and PVA. Potential application of the IPN films in controlled drug delivery was also examined using crystal violet as a model drug. The release rate of the drug was higher at 37°C than 25°C for all IPNs and also increased slightly with decreasing of poly(acrylic acid) content. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008

Electrospinning and Solution Properties of Nafion and Poly(acrylic acid)

In this study, the electrospinning performance and solution properties of Nafion and its blend with another polyelectrolyte, poly(acrylic acid) (PAA), were investigated. Attempts to electrospin pure Nafion at various polymer concentrations (5−35 wt %), solvents, neutralization, and electrospinning conditions resulted in electrospraying rather than electrospinning. However, a polymer solution blend (5 wt %) of Nafion and PAA resulted in beaded fibers at 8 wt % PAA and smooth electrospinning above 12% PAA. Fiber sizes of the blend increased from 90 to 600 nm with increasing PAA content. Dynamic light scattering on pure Nafion solutions in various solvents reveals large aggregates (i.e., dispersion) of various sizes due to polymer backbone and ionic interactions. The lack of sufficient polymer chain entanglement evidenced by low viscosity and aggregate formation in Nafion solutions prohibits fiber formation during electrospinning. The addition of PAA to Nafion modifies the ionic strength of the solvent resulting in suppressed aggregate formation, increased viscosity, and subsequently enhanced polymer chain entanglement. Coincidentally, the onset of suppressed aggregate formation in the blend solution coincides with the electrospraying−electrospinning transition (8% PAA). In addition, thermal treatment enhances water stability of the electrospun blend fibers.

Effects of abrasive particle size and molecular weight of poly(acrylic acid) in ceria slurry on removal selectivity of SiO2/Si3N4 films in shallow trench isolation chemical mechanical planarization

The effects of the molecular weight and concentration of poly(acrylic acid) (PAA) with different primary abrasive sizes in ceria slurry on the nitride film loss, removal rate, film surface roughness, and removal selectivity of SiO2-to-Si3N4 films were investigated by performing chemical mechanical polishing (CMP) experiments using blanket and patterned wafers. In the case of the blanket wafers, we found that for a lower PAA molecular weight, the removal selectivity of SiO2-to-Si3N4 films increased more significantly with increasing PAA concentration in slurry containing a larger primary abrasive size. For the patterned wafers, with a higher PAA molecular weight in the ceria slurry suspension, the erosion of the Si3N4 film was less, but the removed amount was also smaller, and the surface roughness became worse after CMP. These results can be qualitatively explained by the layer of PAA adsorbed on the film surface, in terms of electrostatic interaction and rheological behavior.

Polymer Ionomers for Rapid Prototyping and Rapid Manufacturing by Means of 3D Printing

AbstractSummary: The powder blend of poly(acrylic acid) (PAA) with zinc oxide or zinc oxide/magnesium oxide was applied successfully to produce zinc polycarboxylate during the 3D dispensing of an aqueous ink by means of 3D printers (Z402™ from ZCorporation and Deskmodeler™ from bmt Company). The layer‐by‐layer inkjet printing afforded zinc ionomer 3D objects with excellent water resistance, no inherent color formation and high mechanical and dimensional stabilities. In contrast to the 3D printing of conventional powders such as starch/cellulose/dextrose blends, poly(vinyl alcohol) (PVA) or plaster, no postprinting treatments were required. Excellent dimensional accuracy of the models, as evidenced by very small deviation of the dimensions from those of the corresponding CAD data, was achieved. The mechanical properties improved with increasing PAA content, ink amount (saturation value), decreasing particle size of the sintered zinc oxide ceramic. At high PAA content >7 wt.‐%, post‐treatment with aqueous zinc acetate solution improved the mechanical properties. The setting time of the zinc cements shows no significant effect on the mechanical properties, but on the water resistance of the models. The porosity of the 3D objects, measured by means of X‐ray microtomography (μ‐CT), had profound impact on the variations of the mechanical properties of the 3D objects prepared by 3D printing processes.Comparison of three‐point‐bending tests of commercially available powders with selected zinc cements (ZC1, ZC2, ZC4, ZC19). Commercially available powders printed with recommended values of manufacturer. Zinc cements printed with saturation value 1.14 (Z402™).imageComparison of three‐point‐bending tests of commercially available powders with selected zinc cements (ZC1, ZC2, ZC4, ZC19). Commercially available powders printed with recommended values of manufacturer. Zinc cements printed with saturation value 1.14 (Z402™).

Morphological Evolution of Inorganic Crystal into Zigzag and Helical Architectures with an Exquisite Association of Polymer: A Novel Approach for Morphological Complexity

The morphology of potassium sulfate (K(2)SO(4)) crystals grown in a viscous polymer solution of poly(acrylic acid) (PAA) was remarkably changed from the tilted columnar assembly into zigzag and helical architectures with increasing PAA concentration. The habit modification of orthorhombic K(2)SO(4) with adsorption of PAA molecules on a specified crystal face fundamentally led to the formation of tilted unit crystals. Concurrently with the habit modification, a diffusion-limited condition controlling the assembly of tilted units was achieved in the presence of PAA molecules in the matrix. Various complex morphologies, including zigzag and helical assembly, emerged through the formation of twinned crystals with the variation of the diffusion condition. Understanding the morphogenesis observed in this report would provide a novel approach for sophisticated crystal design by using an exquisite association of organic and inorganic materials.