Molecular Weight Polyacrylic Acid Research Articles

Effect of pH, polymer concentration and molecular weight on the physical state properties of tolfenamic acid

Tolfenamic acid (TA) has been transformed from crystalline to amorphous state through freeze-drying by using varying ratios of polyacrylic acid (PA) at various pH values. The characterization of the films has been carried out using X-ray diffraction, differential scanning calorimetry, Fourier transform infrared (FTIR) spectrometry and scanning electron microscopy. The results showed a gradual change in the solid state properties of TA and a complete transformation into its amorphous form in 1:8, 1:4, 1:2 and 1:1 ratios at pH 3, 4, 5 and 6, respectively. FTIR spectrometry reveals the formation of a yellow polymorphic form of TA. Polymer molecular weight has also been observed to affect the drug transformation and interaction as the low molecular weight PA (Mw ∼ 1800) was found to be most effective followed by its medium (Mv ∼ 450 000) and high molecular weight (Mv ∼ 3 000 000) forms. No signs of recrystallization in the TA–PA films were noted during the 12-week storage period. PA of low molecular weight has also been found more effective in inhibiting the recrystallization of the melt upon cooling thus proving a valuable polymer in producing stable amorphous solid dispersions of TA.

Polyelectrolyte effects on the crystallization phenomena of the lithium carbonate

Anionic polyelectrolyte effects on the lithium carbonate crystallization phenomena were investigated. Li2CO3 crystals were obtained by reactive crystallization with seed crystals. Polyelectrolytes were dissolved into the reactive field before the reaction. Obtained crystals were observed with scanning electron microscopy (SEM) and crystal size and agglomeration degree were measured by the SEM images. The results show that Li2CO3 crystallized different shape and size from absence of polyelectrolyte in those reactive fields. Especially polyacrylic acid (PAA) improved on the agglomeration of the crystals and shaped them high aspect needles. Thus other experimental conditions including PAA molecular weight and concentration, reaction time, supersaturation by Li concentration were investigated in addition. As a result, obtained crystals were not different in each PAA molecular weight reactive fields. Meanwhile PAA concentration has optimum range. Li2CO3 formed less agglomeration and higher aspect around 1g/l. In the concentration, Li2CO3 did not agglomerate regardless of aging time and Li concentration. Moreover crystals became rectangle shape in higher Li concentration.(020) face intensity of the rectangle shape crystals increased according to XRD pattern. PAA affected the facial growth. These results may provide a method of morphological change and clearly crystallization of Li2CO3.

The influence of poly(acrylic) acid number average molecular weight and concentration in solution on the compressive fracture strength and modulus of a glass-ionomer restorative

Objectives The aim was to investigate the influence of number average molecular weight and concentration of the poly(acrylic) acid (PAA) liquid constituent of a GI restorative on the compressive fracture strength ( σ) and modulus ( E). Methods Series of PAA solutions for eight experimental PAAs with molecular weights ranging from 5000 to 200,000 were prepared at concentrations ranging from 10 to 60%. The PAA number average molecular weights were determined using gel permeation chromatography and the viscosity at each concentration was determined using a digital viscometer. The PAA solutions were hand-mixed with a commercial GI restorative powder (Ionofil Molar; Voco, Cuxhaven, Germany). σ and E were determined at 24 h using cylindrical (6 mm height, 4 mm diameter) specimens ( n = 20). Data was analyzed using regression analyses and two-way analyses of variance at p < 0.05. Results Regression analyses showed a significant reduction in PAA solution viscosity with reducing PAA number average molecular weight. Two-way ANOVAs for σ and E indicated a significant interaction of number average molecular weight × concentration ( p < 0.001 and p < 0.001, respectively). Quadratic regression analyses showed significant curvature (n-shaped curves) within σ and E data for individual PAA number average molecular weights with increasing concentration. As a result, the optimum PAA concentration for each PAA number average molecular weight was determined from the curve vertexes. Significance The choice of PAA molecular weight and concentration and the subsequent viscosity of the PAA solution have a significant influence on the σ and E of a GI restorative, however, the relationship is not a simple one.

Influence of solution pH on stability of aluminum oxide suspension in presence of polyacrylic acid

The effect of solution pH and molecular weight of polyacrylic acid (PAA) on its adsorption as well as on stabilization-floculation properties of the colloidal Al2O3 and electrolyte solution systems was studied. The measurements showed that at pH = 6, the presence of the polymer of molecular weight 2 000 and 240 000 does not change stability of Al2O3 suspension. However at pH =3 and 9 the effect of polyacrylic acid is significant. At pH = 3 it creates destabilization of the suspension while at pH = 9 PAA it improves significantly the stability of Al2O3. It was shown that the increase in solution pH affects conformation of adsorbed macromolecules which causes the decrease in PAA adsorbed amount and thickness of polymer adsorption layer. By comparing the values of diffusion layer and surface charges, main effects responsible for the decrease in surface charge and ζ potential of the solid in the presence of the polymer as well as suspension stability were determined.

Influence factors on electrochemical properties of Li 4Ti 5O 12/C anode material pyrolyzed from lithium polyacrylate

Spinel Li 4Ti 5O 12/C was synthesized by one-step solid-state reaction route using lithium polyacrylate (PAALi) as lithium and carbon sources, and TiO 2 as titanium source. The characteristics of Li 4Ti 5O 12/C composites were determined by X-ray diffraction, scanning electron microscopy, transmission electron microscopy and thermogravimetric-differential thermal analysis methods. Their electrochemical performances were investigated by cyclic voltammograms, constant current charge–discharge and rate charge–discharge. It was found that molecular weight of polyacrylic acid (PAA), heating rate and sintering duration directly affected the physical and electrochemical performances of Li 4Ti 5O 12/C composites. The Li 4Ti 5O 12/C composites with the optimized electrochemical performances were obtained in the following conditions, i.e., PAA with the molecular weight of 10,000, heating rate of 20 °C min −1 and sintering duration of 8 h. At charge–discharge rate of 4 C and 8 C, the optimized sample showed discharge capacities of 148.4 and 142.4 mAh g −1, with capacity retention of 94.48 and 90.53% after 50 cycles, respectively. Even at 20 C, its discharge capacity was 116.0 mAh g −1 with capacity retention of 87.61% after 50 cycles.

A spectroscopic investigation into the setting and mechanical properties of titanium containing glass polyalkenoate cements

Titanium (Ti) implants are extensively used in a number of biomedical and dental applications. This work introduces Ti into the glass phase of a zinc based glass polyalkenoate cement (GPC) and investigates changes in handling and mechanical properties considering two molecular weight polyacrylic acids (PAA), E9 and E11. Considering the handling properties, the working time (T (w)) increased from 50 s(E9), 32 s(E11) (BT 101, Ti-free) to 169 s(E9), 74 s(E11) with TW-Z (highest Ti content), respectively. The setting time (T (s)) increased from 76 s(E9), 47 s(E11) (BT 101) to 303 s(E9), 232 s(E11) with TW-Z, respectively. Ti was also found to have a significant increase on both compressive (sigma (c)) and biaxial flexural strength (sigma (f)), where sigma (c) increased from 36 MPa(E9), 56 MPa(E11) (BT 101) to 56 MPa(E9) and 70 MPa(E11) with TW-Z respectfully. sigma (f) also increased from 11 MPa(E9), 22 MPa(E11) (BT 101) to 22 MPa(E9) and 77 MPa(E11) with TW-Z, respectively. No increase in mechanical properties was evident with respect to maturation. Raman Spectroscopy was employed to investigate changes in glass structure and the setting of the cements with. This revealed increased glass network disruption with increasing TiO(2) content and matured cement setting with TW-Z as compared to the control BT 101. FT-IR was then employed to investigate any additional setting mechanism and changes with time. Spectroscopy determined that Ca(2+)/Sr(2+)PAA complexes are primarily responsible for the setting and mechanical strength with no changes occurring over time.

Effect of polyacrylic acid molecular weight on the floc stability during prolonged settling

Settling tests are normally carried out for short durations to study dewatering characteristics of materials. Natural gravitational settling and associated consolidation processes continue for longer periods before a substantially stable structure is attained. For example, the structural stabilization of a tailing dam involving fine particulates continues for years. To simulate the conditions of gravitational stabilization of particulate materials in the presence of polymers, in this investigation batch settling trials were carried out for prolonged durations with the model colloidal alumina and polyacrylic acid (PAA) flocculants of different molecular weights. It is observed that a critical molecular weight exists where superior flocculation and consolidation performances are observed due to synergistic effects of charge neutralization and bridging. Based on the interesting findings, it is suggested that the design of an optimum dewatering reagent scheme need not be based on short duration sedimentation and/or filtration trials alone. The long-term gravitational stabilization behaviour is an important area of concern from environmental and safety points of view and should be appropriately addressed.

Characteristics, morphology, and stabilization mechanism of PAA250K-stabilized bimetal nanoparticles

Injection of bimetal (Pd/Fe) nanoparticles was evidenced as a promising treatment to remediate trichloroethene (TCE) polluted groundwater. However, the particles usually aggregate rapidly and result in a very limited migration distance. This study employed poly acrylic acid (PAA) for the synthesis of stable bimetal nanoparticles (SBN) by selecting appropriate PAA molecular weight and dosage to reduce particle aggregation. In addition, this study elucidated the SBN stabilization mechanism by analyzing morphology and characteristics. The results of TCE dechlorination and SBN stabilization experiments indicate that the bimetal nanoparticles modified with PAA250K exhibit better reactivity and stability characteristics than did other such nanoparticles. The SBN bind chemically onto PAA250K via the carboxylic group and bidentate pattern bridging, which could provide both electrostatic and steric repulsion to prevent particle aggregation. Therefore, the SBN exhibited a higher dechlorination effect than did bare bimetal. The morphology of SBN shown in the transmission electron microscopy (TEM) images exhibits capsule-like and wire-like structures instead of a single particle dispersed in the slurry. The results of this work can preliminarily elucidate the SBN's morphology, dispersion, and size distribution.

Comparison of an experimental bone cement with a commercial control, Hydroset™

Glass polyalkenoate cements based on strontium calcium zinc silicate glasses (Zn-GPCs) and high molecular weight polyacrylic acids (PAA) (MW; 52,000-210,000) have been shown to exhibit mechanical properties and in vitro bioactivity suitable for arthroplasty applications. Unfortunately, these formulations exhibit working times and setting times which are too short for invasive surgical applications such as bone void filling and fracture fixation. In this study, Zn-GPCs were formulated using a low molecular weight PAA (MW; 12,700) and a modifying agent, trisodium citrate dihydrate (TSC), with the aim of improving the rheological properties of Zn-GPCs. These novel formulations were then compared with commercial self-setting calcium phosphate cement, Hydroset, in terms of compressive strength, biaxial flexural strength and Young's modulus, as well as working time, setting time and injectability. The novel Zn-GPC formulations performed well, with prolonged mechanical strength (39 MPa, compression) greater than both vertebral bone (18.4 MPa) and the commercial control (14 MPa). However, working times (2 min) and rheological properties of Zn-GPCs, though improved, require further modifications prior to their use in minimally invasive surgical techniques.

Growth of nanofibrous barium carbonate on calcium carbonate seeds

Fibrous barium carbonate (BaCO 3/witherite) crystals 50–100 nm in diameter and several microns in length were grown on calcium carbonate (CaCO 3) seeds at temperatures as low as 4 °C. The BaCO 3 fibers were deposited onto calcite rhombs or CaCO 3 films using the polymer-induced liquid-precursor (PILP) process, which was induced with the sodium salt of polyacrylic acid (PAA). The structure and morphology of the resultant fibers were investigated using scanning electron microscopy (SEM), transmission electron microscopy (TEM), selected-area electron diffraction (SAED), and polarized light microscopy (PLM). Fibers were successfully grown on calcite seeds of various morphologies, with a range of barium concentrations, and PAA molecular weight and concentration. Two categories of fibers were grown: straight and twisted. Both types of fibers displayed single-crystalline SAED diffraction patterns, but after examining high-resolution TEM lattice images, it was revealed that the fibers were in fact made up of nanocrystalline domains. We postulate that these nanocrystalline domains are well aligned due to a singular nucleation event (i.e., each fiber propagates from a single nucleation event on the seed crystal) with the nanocrystalline domains resulting from stresses caused by dehydration during crystallization of the highly hydrated precursor phase. These BaCO 3 fibers grown on calcite substrates further illustrate the robustness and non-specificity of the PILP process.

Electrochemical fabrication of conducting polymer poly(3,4-ethylenedioxythiophene) (PEDOT) nanofibrils on microfabricated neural prosthetic devices

This paper describes methods for electrochemically polymerizing conducting polymer poly(3,4-dioxyethylenethiophene) (PEDOT) nanofibrils on microfabricated neural prosthetic devices from aqueous solutions containing polyacrylic acid (PAA). These fibrils have characteristic sizes ranging from 100 to 1000 nm in diameter, depending on the concentration, molecular weight of PAA and thickness of the film. The PEDOT nanofibril-coated electrodes have significantly lower electrical impedance due to their higher effective surface area. We propose a mechanism of nanofibril formation involving locally anisotropic variations in EDOT monomer transport and PEDOT film growth due to segregation of the PAA counter-ions. This deposition method provides an improvement in the electrical properties by increasing the effective surface area of the electrodes, while still maintaining the overall small electrode size. It is also opens up new reliable and reproducible strategies for the direct electrochemical polymerization of conducting polymer nanofibrils on a variety of electrodes.

Preparation of polyelectrolyte multilayer membranes by dynamic layer-by-layer process for pervaporation separation of alcohol/water mixtures

In the past decades, the layer-by-layer (LBL) adsorption of oppositely charged polyelectrolytes has proven to be a promising method for the preparation of polyelectrolyte multilayer membranes. However, to obtain a good separation capability, LBL adsorption involved relatively long periods because 50–60 bilayers were normally required. The aim of this study was to develop such a new method that would allow simplification of the LBL procedure. LBL adsorption was proposed to proceed under a dynamic condition to prepare polyelectrolyte multilayer membranes. The polyacrylic acid (PAA) and polyethyleneimine (PEI) were alternatively deposited on polyethersulfone (PES) ultrafiltration support membrane under a pressure of 0.1 MPa. The polyelectrolyte multilayer membranes prepared by dynamic LBL process were compared with those prepared by the static LBL process for the pervaporation separation of water–ethanol mixture. The results suggested that a relatively high separation factor could be obtained with only four composite bilayers by using dynamic LBL process. The preparative conditions including bilayer number, filtration time of the first PAA layer, reaction time, ratio between polayanion and polycation concentrations, PAA molecular weight and salt addition were investigated. The pervaporation conditions such as feed temperature and water concentration in the feed were also evaluated. Under the temperature of 40 °C, the separation factor and the permeate flux of the polyelectrolyte multilayer membranes were about 1207 and 140 g/(m 2 h), respectively.

Size and pH effect on electrical and conformational behavior of poly(acrylic acid): Simulation and experiment

Monte Carlo simulations, experimental titrations and fluorescence correlation spectroscopy experiments were used to investigate the conformational and electrical properties of polyacrylic acids (PAA). On the one hand, titration curves were calculated to get an insight into the role of pH on the degree of ionization and conformation of PAA chains. On the other hand, experimental potentiometric titrations of PAA were also achieved for different PAA molecular weights and compared to the calculated titration curves obtained by Monte Carlo coarse grained simulations. It was found that for a large range at intermediate PAA ionizations, a good correlation is obtained between experimental and simulations data thanks to the prominence of electrostatic interactions in this domain. The effect of ionic concentration and PAA molecular weight on the titration curves was also investigated. In order to get a better understanding of PAA conformational behavior, we also investigated PAA diffusion properties in aqueous solutions as a function of pH and ionic strength by fluorescence correlation spectroscopy (FCS), thanks to its high sensitivity to measure diffusion coefficients of tracer solutes. Good qualitative agreements were observed between experimental diffusivities and polymer properties calculated from MC simulations. It was shown that the high molecular weight PAA chains display more significant changes in diffusivity in agreement with the ionization degrees and conformational changes observed in the simulations.

Influence of the ionic strength on the adsorption properties of the system dispersed aluminium oxide–polyacrylic acid

The influence of ionic strength, pH of the solution and molecular weight of polyacrylic acid (PAA) on its adsorption and the electrical double layer (Al2O3/polyelectrolyte solution) properties have been examined. The measurements show that the adsorption increases with increasing ionic strength and molecular weight of the polymer, whereas the increase in pH reduces the adsorption. The thickness of the PAA adsorption layer onto aluminium oxide and the expansion coefficient were also calculated. The increase in ionic strength, pH of the solution and polymer molecular weight causes an increase in adsorption layer thickness and expansion coefficient of PAA.

Influence of molecular weight of polyacrylic acid on the rate of copper dissolution

The weight of polyacrylic acid adsorbed on copper from an aqueous solution and the rate of copper dissolution in the presence of hydrogen peroxide as functions of molecular weight of the polymer were studied.

Application of the SAXS method and viscometry for determination of the thickness of adsorbed polymer layers at the ZrO 2–polymer solution interface

The authors studied the influence of the molecular weight of polyacrylic acid (PAA) and polyacrylamide (PAM), solution pH and ionic strength, and the background electrolyte type on adsorption and the thickness of polyelectrolyte adsorption layers formed on ZrO 2 surface. Carboxyl groups distributed along PAA and PAM chains were shown to be responsible for their interface conformation, which directly influences the thickness of the adsorbed polyelectrolyte layers. Bonding of macromolecules with solid surface occurs through the hydrogen bridges of these groups. Two methods were applied to determine the PAA and PAM adsorption layer thickness on ZrO 2, i.e., SAXS (small angle X-ray scattering) and viscometry. Despite some limitations of the SAXS method resulting from the relationship between the size of solid pores, polymer molecular weight, and conformation of the adsorbed macromolecule, all obtained SAXS results were very close to those calculated from viscometry data.

Effect of polyacrylic acid molecular weight and SiO&lt;sub&gt;2&lt;/sub&gt;/Al&lt;sub&gt;2&lt;/sub&gt;O&lt;sub&gt;3&lt;/sub&gt; ratio on the mechanical strength of glass-polyalkenoate cements

Los cementos de polialquenoato vitreo son ampliamente utilizados para aplicaciones dentales. Con el proposito de entender mejor los procesos involucrados en las reacciones de formacion de este tipo de cementos y de explorar su uso en aplicaciones ortopedicas, en el presente trabajo se realizo un estudio para analizar el efecto del peso molecular del acido poliacrilico y de la proporcion silice/ alumina sobre la resistencia a la compresion y las caracteristicas microestructurales de cementos de polialquenoato vitreo. Las probetas obtenidas fueron sometidas a pruebas de compresion y al analisis por microscopia electronica de barrido (MEB) y por espectroscopia infrarroja por transformada de Fourier (IRTF). En una primera serie de experimentos se consideraron pesos moleculares promedio del acido poliacrilico de 2000, 9700, 15268 y 64000, manteniendose constante la relacion SiO2/Al2O3 en un valor de 2,5. En una segunda serie de experimentos se consideraron relaciones SiO2/Al2O3 de 2,1; 1,67; 1,25; 0,95 y 0,8; utilizando acido poliacrilico con peso molecular constante de 64000. Los maximos valores de resistencia mecanica (82,5 MPa) se alcanzaron cuando el peso molecular del acido poliacrilico fue de 64000 y la relacion SiO2/Al2O3 en el vidrio fue de 1. Estos valores de resistencia a compresion de los cementos de polialquenoato vitreo son similares a los reportados para cementos a base de polimetilmetacrilato, lo cual sugiere su uso potencial en aplicaciones ortopedicas. Finalmente, se evaluo cualitativamente la reactividad de los vidrios y la presencia de grupos funcionales �COOH sin reaccionar utilizando IRTF, asi como la separacion de fases en vidrios con relaciones SiO2/Al2O3 > 1 y la reactividad superficial de las particulas de vidrio empleando espectroscopia de dispersion de rayos X (DERX) en el MEB. A fin de optimizar la resistencia a compresion de los cementos de polialquenoato vitreo, trabajos futuros pueden ser orientados a mejorar la reactividad de los vidrios, a optimizar la relacion polimero / vidrio y a utilizar particulas de vidrio de tamano submicronico

Effect of doping polyacrylic acid with some dopants as studied by different techniques

The molecular weight of polyacrylic acid (PAA) was determined by a viscometric method using NaNO3 as solvent at 30°C. The specific electric conductivities (σ) of PAA as well as PAA doped with carbon black (CB), chromium oxide (Cr2O3), and cupferron with different concentrations (from 0.25 to 1 wt %) were measured at a temperature range 360–400 K. IR spectra of some polymers were determined and it was shown that when PAA was doped with 0.5 wt % CB, a COC band appeared at 775–875 cm−1. The positron annihilation lifetime (PAL) spectra in PAA doped with the above-mentioned dopants were measured as a function of their concentrations. It was observed that the short lifetime intensity I1 decreased, whereas the intermediate lifetime intensity I2, which is related to the conductivity of the material, increased with increasing the wt % of Cr2O3 and cupferron as well as at low concentrations of CB. These results are discussed in terms of the conducting island model. It was found that there were distinct positive relationships between σ and I2. © 2002 John Wiley & Sons, Inc. J Appl Polym Sci 84: 877–883, 2002; DOI 10.1002/app.10381

Effect of doping polyacrylic acid with some dopants as studied by different techniques

AbstractThe molecular weight of polyacrylic acid (PAA) was determined by a viscometric method using NaNO3 as solvent at 30°C. The specific electric conductivities (σ) of PAA as well as PAA doped with carbon black (CB), chromium oxide (Cr2O3), and cupferron with different concentrations (from 0.25 to 1 wt %) were measured at a temperature range 360–400 K. IR spectra of some polymers were determined and it was shown that when PAA was doped with 0.5 wt % CB, a COC band appeared at 775–875 cm−1. The positron annihilation lifetime (PAL) spectra in PAA doped with the above‐mentioned dopants were measured as a function of their concentrations. It was observed that the short lifetime intensity I1 decreased, whereas the intermediate lifetime intensity I2, which is related to the conductivity of the material, increased with increasing the wt % of Cr2O3 and cupferron as well as at low concentrations of CB. These results are discussed in terms of the conducting island model. It was found that there were distinct positive relationships between σ and I2. © 2002 John Wiley &amp; Sons, Inc. J Appl Polym Sci 84: 877–883, 2002; DOI 10.1002/app.10381

Rheological Properties and Gelation Threshold of Temperature Induced Forming (TIF) Alumina Suspensions with Variation in Molecular Weight of Polyacrylic Acid

The effect of polyacrylic acid (PAA) molecular weight on the rheological properties of TIF aqueous alumina suspensions that have gelation behavior at elevated temperature is studied. The volume fraction gelation threshold of such alumina suspensions is estimated based on the viscoelastic properties. The volume fraction gelation thresholds are 0.20 and 0.35 for the alumina suspensions containing 0.04 wt% PAA of Mw 10,000 and Mw 5,000, respectively. Both values are higher than that of the suspensions with 0.04 wt% PAA of Mw 50,000, which is about 0.15. These results can give us guidance to tailor both the composition and gelation character of the TIF alumina suspensions for direct casting.