Molecular Weight Polyacrylic Acid Research Articles

Bifunctional low molecular weight polyacrylic acid as aqueous binder and coating agent enables high performance LiMn2O4 cathode for lithium-ion batteries

LiMn2O4 is considered to be a promising cathode material for lithium-ion batteries due to its decent energy density, low price and environmental benignity. However, the problems of Mn dissolution, migration and deposition during the cycle, seriously affect its lifespan, especially at high temperature. In this study, we developed a strategy by which we killed two birds with one stone. A low molecular weight polyacrylic acid (PAA) mixed with sodium carboxymethyl cellulose (CMC) is applied as binder and coating agent for cathode particles at the same time. The conventional and environmental unfriendly polyvinylidene difluoride (PVDF)-N-methylpyrrolidone (NMP) system is replaced by the cheap and green aqueous binder with improved adhesive effect. Furthermore, the binder-based surface coating layer not only alleviates the side reaction between the electrolyte and the cathode particles, but also chelates the dissolved Mn2+ by the large amount of carboxyl groups in PAA molecules and so prevents the following migration and deposition of Mn2+. In the button half-cell with low molecular weight PAA based binder, the capacity retention reaches 94.1 % after 1000 cycles at room temperature and 92.0 % after 200 cycles at 60 degrees centigrade. Meanwhile, 18650-type cylindrical cells were prepared with this binder, which shows a great high temperature storage performance. After the cell was held at 60 degrees centigrade for 25 days at full charged state, the internal resistance increased by only 1.25mΩ, the voltage decreased by only 0.1 V, the residual capacity retention and recovery capacity retention reaches 85.6 % and 92.2 %. This work shows the great potential of the aqueous binder in dealing with the problem of Mn dissolution during the cycling of manganese-based cathode materials for lithium-ion batteries.

The Effects of Endoplasmic Reticulum Stress via Intratracheal Instillation of Water-Soluble Acrylic Acid Polymer on the Lungs of Rats.

Polyacrylic acid (PAA), an organic chemical, has been used as an intermediate in the manufacture of pharmaceuticals and cosmetics. It has been suggested recently that PAA has a high pulmonary inflammatory and fibrotic potential. Although endoplasmic reticulum stress is induced by various external and intracellular stimuli, there have been no reports examining the relationship between PAA-induced lung injury and endoplasmic reticulum stress. F344 rats were intratracheally instilled with dispersed PAA (molecular weight: 269,000) at low (0.5 mg/mL) and high (2.5 mg/mL) doses, and they were sacrificed at 3 days, 1 week, 1 month, 3 months and 6 months after exposure. PAA caused extensive inflammation and fibrotic changes in the lungs' histopathology over a month following instillation. Compared to the control group, the mRNA levels of endoplasmic reticulum stress markers Bip and Chop in BALF were significantly increased in the exposure group. In fluorescent immunostaining, both Bip and Chop exhibited co-localization with macrophages. Intratracheal instillation of PAA induced neutrophil inflammation and fibrosis in the rat lung, suggesting that PAA with molecular weight 269,000 may lead to pulmonary disorder. Furthermore, the presence of endoplasmic reticulum stress in macrophages was suggested to be involved in PAA-induced lung injury.

Mussel-inspired Self-assembly into Polymer Coatings of Different Molecular Weight Electrolytes for Enhanced Self-healing and Corrosion Properties.

Self-healing coatings offer tremendous application prospects in the field of preventing metal corrosion because of their superior functionality. The coordination of barrier performance and self-healing ability, however, continues to be difficult. Herein, a polymer coating based on polyethyleneimine (PEI) and polyacrylic acid (PAA) with self-repairing and barrier ability was designed. Introducing the catechol group into the anti-corrosion coating increases the adhesion and self-healing efficiency of the coating, providing a guarantee for the long-term stable bonding between the anti-corrosion coating and the metal substrate. Small molecular weight PAA polymers are added to polymer coatings to increase their self-healing capabilities and corrosion resistance. Because layer-by-layer assembly creates reversible hydrogen bonds and electrostatic bonds that help the coating repair itself when it is damaged, and because the traction of small molecular weight polyacrylic acid speeds up this process. When polyacrylic acid (PAA) with a molecular weight of 2000 was present in the coating at a concentration of 1.5 mg/mL, the coating's self-healing capability and corrosion resistance were at their peak. The PEI-C/PAA45W -PAA2000 coating completed the self-healing within 10 min, and the corrosion resistance efficiency (Pe ) was as high as 90.1 %. The polarization resistance (Rp ) was maintained at 7.67×104 Ω cm2 after immersion for more than 240 h. It was better than other samples in this work. The polymer provides a new idea for the prevention of metal corrosion.

Effect of the Addition of Polyacrylic Acid of Different Molecular Weights to Coagulation Bath on the Structure and Performance of Polysulfone Ultrafiltration Membranes

Membrane fouling is a serious issue in membrane technology which cannot be completely avoided but can be diminished. The perspective technique of membrane modification is the introduction of hydrophilic polymers or polyelectrolytes into the coagulation bath during membrane preparation via non-solvent-induced phase separation. The influence of polyacrylic acid (PAA) molecular weight (100,000, 250,000 and 450,000 g·mol-1) added to the aqueous coagulation bath (0.4-2.0 wt.%) on the polysulfone membrane structure, surface roughness, water contact angle and zeta potential of the selective layer, as well as the separation and antifouling performance, was systematically studied. It was found that membranes obtained via the addition of PAA with higher molecular weight feature smaller pore size and porosity, extremely high hydrophilicity and higher values of negative charge of membrane surface. It was shown that the increase in PAA concentration from 0.4 wt.% to 2.0 wt.% for all studied PAA molecular weights yielded a substantial decrease in water contact angle compared with the reference membrane (65 ± 2°) (from 27 ± 2° to 17 ± 2° for PAA with Mn = 100,000 g·mol-1; from 25 ± 2° to 16 ± 2° for PAA with Mn = 250,000 g·mol-1; and from 19 ± 2° to 10 ± 2° for PAA with Mn = 450,000 g·mol-1). An increase in PAA molecular weight from 100,000 to 450,000 g·mol-1 led to a decrease in membrane permeability, an increase in rejection and tailoring excellent antifouling performance in the ultrafiltration of humic acid solutions. The fouling recovery ratio increased from 73% for the reference membrane up to 91%, 100% and 136% for membranes modified with the addition to the coagulation bath of 1.5 wt.% of PAA with molecular weights of 100,000 g·mol-1, 250,000 g·mol-1 and 450,000 g·mol-1, respectively. Overall, the addition of PAA of different molecular weights to the coagulation bath is an efficient tool to adjust membrane separation and antifouling properties for different separation tasks.

Role of silicon-graphite homogeneity as promoted by low molecular weight dispersants

This study explores low molecular weight polymers with the same chemical repeat structure as high molecular weight poly acrylic acid (PAA) and lithium poly acrylic acid (LiPAA) binders which act as a dispersant to improve the silicon-graphite electrode performance. The electrodes which utilize LiPAA as a dispersant perform, on average, the best with respect to the maximum capacity (compared to theoretical), rate performance, and capacity retention with time. These electrodes also have the poorest dispersion of binder, indicating that the poor binder dispersion is essential to electrode performance. In contrast, this study shows that electrodes formulated using PAA had good dispersion and performs the worst in cycling. Finally, this work demonstrates that the binder is not uniformly distributed in the electrode, but rather resides in local regions. The results indicate these regions accommodate volume expansion during cycling. • Surface charge can control dispersion and binder adsorption. • Dispersant & binder chemistry can control rheology & homogeneity. • Optimized formulations lead to optimized performance.

Effects of polyacrylic acid molecular weights on V2C-MXene nanocoatings for obtaining ultralow friction and ultralow wear in an ambient working environment

Two modified V2C-MXene nanocoatings are prepared through different molecular weights of polyacrylic acid (polyacrylic acid with ∼4 50 000 is marked as LPAA, and polyacrylic acid with ∼4 000 000 is marked as HPAA) and two-dimensional V2C-MXene. Their properties are characterized using a ball-on-disc tribometer, three-dimensional white-light interferometry topography images, optical microscope, Raman spectrometer, focused ion beam/scanning electron microscope and high-resolution transmission electron microscope/energy dispersive X-ray spectrometer (HRTEM/EDS). As a result, an ultralow friction (μ ≈ 0.073 ± 0.024) and an ultralow wear (3.41 × 10-7 mm3 N-1 m-1 for ball scar, and 7.49 × 10-8 mm3 N-1 m-1 for disc track) are achieved for the LPAA@V2C vs. steel ball system tested under 4 N in the air through tribo-physicochemical interactions. During the rubbing process, the LPAA@V2C nanocoating is transferred onto counter-bodies to form mixed-phase lubricative tribofilms. Monitoring via a HRTEM/EDS, the mixed-phase lubricative tribofilms are found to be mainly composed of amorphous carbon phases containing O and V and layered nano-debris along the sliding surface. The tribofilm's stable structure is the key to realizing ultralow friction and ultralow wear through the LPAA modification. These findings disclose that MXene-based nanomaterials can be applied for material engineering and mechanical engineering under common working conditions.

ZnAl hydrotalcites modified with nanocomposites nZVI–PAA for environmental remediation

Diffraction patterns of polyacrylic acid (PAA) encapsulated-(Fe)-modified ZnAl hydrotalcite (ZnAlH) showed the integration of Fe in the H lattice, resulting in a hybrid nanocomposite (Fe-PAA-ZnAlH), which was mainly verified with the characteristic shift in the 59–63° (2θ) region of the ZnAlH (110) reflection plane. The rise in the unit cell parameters (c and a ) as the Fe % incremented, denoted incorporation of Fe in the ZnAlH red. Nonetheless, changes in the immobilizer molecular weight (PAA MW) from 1250 kDa to 5.1 kDa did not cause a difference in the distance between layers (c parameter) but in the cation-cation separation ( a parameter), which meant that the nanoparticle was not located between layers, but in the lattice. The resulting band gap energies of the calcined hybrid nanocomposites were among 1.07–1.21 eV, which is an additional support of Fe +3 integration, suggesting insertion of Fe +3 3d orbitals between the valence and the conduction band of ZnO. Furthermore, nZVI were prepared through a pre-agglomeration reduction method, where COOH-groups were bound to metal cations. Initially, aqueous Fe +2 was bound to PAA [Fe +2 -PAA], then reduced to obtain enclosed hybrid (nZVI-PAA). Less stability and more aggregation were observed with the lower molecular weight PAA. Additionally, PAA dissociation caused by pH changes affected the clustering of the nZVI particles. At higher MW, the hydrodynamic diameter and size distribution become smaller and tighter, respectively, allowing a more monodispersed population with sphere shape and organized in core–shell beads chains.

In vitro osteogenic performance of two novel strontium and zinc-containing glass polyalkenoate cements.

Glass polyalkenoate cements (GPCs) are under investigation as potential bone adhesives, as they may provide an alternative to polymethylmethacrylate-based cements. GPCs containing strontium (Sr) and zinc (Zn) in place of aluminium (Al) are of particular interest because these ions are known stimulators of osteoprogenitor differentiation. GPCs have been manufactured from a novel bioactive glass (SiO2 :0.48, ZnO:0.36, CaO:0.12, SrO:0.04) in the past, but, while such materials have been assessed for their influence on viability, their influence on osteogenic function has not been investigated until now. For this study, two GPCs were formulated from the same glass precursor evaluated in previous studies. These GPCs were named GPC A and GPC B, and they differed in glass particle size, polyacrylic acid molecular weight, and their powder: liquid ratios. The effect of these two GPCs on osteogenic differentiation of primary rat osteoblasts were evaluated using three culture systems: culture with dissolution extracts, indirect contact with transwell-inserts and direct contact. Additionally, the degradation characteristics of GPCs were assessed, including their interfacial pH and surrounding pH. The experimental outcomes revealed that collagen deposition, alkaline phosphatase expression, and mineralization were largely dependent on GPC composition as well as the mode of interaction with cells. These markers were found to be significantly elevated in response to GPC A's dissolution products. However, osteogenic differentiation was inhibited when osteoblasts were cultured indirectly and directly with GPCs, with, overall, GPC B significantly outperforming GPC A. These results suggest that GPC degradation products effect osteogenic differentiation in a dose-dependent manner.

Influence of molecular weight on polyacrylic acid flocculation of sub-micron titanium dioxide

This paper reports the effect of the molecular weight of polyacrylic acid (PAA) on the flocculation of sub-micron titanium dioxide particles. The average molecular weight (MW) of the three studied PAAs were 140,000, 512,000 and 1,483,000 g/mol, respectively. The flocculation process was studied by several techniques including focused beam reflectance measurement (FBRM), photometric dispersion analyses (PDA), settling tests in graduated cylinders. The adsorption density of the PAAs on the titanium dioxide surface was measured by an elemental analyzer, and the floc structure was studied by scanning electron microscope and fractal dimension analysis using an optical microscope. The results showed that the flocs formed with the high MW PAA had larger sizes than the flocs generated with medium MW PAA. However, the medium MW PAA resulted in better flocculation performance, with faster settling rate and clearer supernatant. This observation was in contrast to the general perception in the literature that high MW polymer flocculants have better flocculation performance. The porosity of the flocs generated by the high MW PAA was larger than flocs by the medium MW PAA, leading to lower density flocs. This was found to be the main reason for the slow settling rate of the high MW PAA despite the larger floc size. Finally, despite the different settling rates, the PAAs with different MWs all showed their optimum flocculation performance at about 3.3 % of a monolayer coverage on the TiO2 surfaces.

Polyacrylic acid and polyvinyl alcohol-based polymer complexes and hydrogels

In aqueous solution, in the acidic environment (pH <3), water-soluble complexes are formed based on polyacrylic acid (PAA) and polyethyleneglycol with a molecular weight of more than 6000 or on polyvinyl alcohol (PVA). The conditions for obtaining hydrogel based on polyacrylic acid and polyvinyl alcohol with a high degree of swelling (about 500 g of water/g of polymer) were determined: pH <3, temperature 120-140 ° С . The degree of interaction of polymers is directly proportional to the content of polyvinyl alcohol in the initial mixture in the range of the molar PVA and PAA ratios from 1 : 1 to 10 : 1, the temperature and duration of heat treatment and is inversely proportional to the molecular weight of polyacrylic acid. The equilibrium degree of hydrogel swelling increases at the pH of the swelling medium above 6, and the swelling rate depends on the solvent diffusion into the hydrogel and is determined by the size of its particles and the swelling conditions (washing, mixing, etc.).

Polyelectrolyte complexes of polyacrylic acid with oligovalent organic counterions

In contrast to formation of polyelectrolyte-surfactant and interpolyelectrolyte complexes, formation of polyelectrolyte complexes with low molecular weight oligovalent organic counterions is almost not studied. This work investigates the interaction of polyacrylic acid (PAA) of different molecular weights (Mn = 2000 and 26,700) with oligoethylenimines having 2–6 amino groups. Formation of colloid or water-insoluble ionic complexes was found as a result of ionic cross-linking of PAA by oligocationic counterions with not less than three amino groups in the molecule. The formed complexes redissolve at certain pH values and NH/COOH ratios in the solution. Complexes sensitive to certain pH could be obtained by changing the number of amino groups in the cross-linker and PAA molecular weight. The particle size of the complexes under consideration is almost independent of the cross-linker and can be controlled by varying the polymer concentration for PAA-2000 complexes and by NH/COOH ratio for PAA-26700 complexes. According to SEM and AFM, complexes of PAA-2000 with oligoethylenimines form hollow spherical particles in dilute solutions and precipitate to form gel-like films in concentrated solutions.

Polyacrylic Acid‐Based Coordination Supramolecular Elastomer with High Strength, Excellent Fatigue‐Resistance, and Self‐Recovery Properties

AbstractSupramolecular elastomers have attracted extensive attention due to their excellent mechanical properties. Herein, inspired by the concept of a dual cross‐linked network structure, a dual‐component coordination supramolecular elastomer is prepared via photopolymerization of three monomers combined with zinc ion (Zn2+)‐crosslinked low molecular weight polyacrylic acid (PAA). The covalent network of three monomers serves as a soft component forming the supporting network. The network of Zn2+ crosslinked low molecular weight PAA forms the hard component. The covalent network is crosslinked and locked by the coordinated network. This compact network contributes to improving the comprehensive mechanical properties. The optimal elastomer is that the molar ratio of carboxylic of low molecular weight PAA with Zn2+ is 1:0.5. The tensile and compression stress of the optimal elastomer are 4.08 and 6.90 MPa, respectively. The loading–unloading cycles can reach 1000 times without fracture. The self‐recovery ratios of the tensile and compression modes reaches 80% and 95%, respectively.

Effect of PAA-coated magnetic nanoparticles on the performance of PVA-based hydrogels developed to be used as environmental remediation devices

In the present work, the effect of the incorporation of polyacrylic acid (PAA)–coated magnetic nanoparticles (MNPs) on the performance of polyvinyl alcohol (PVA)–based hydrogels for water remediation was studied. Ferrogels from PVA and PAA-coated MNPs were prepared through the ecocompatible freezing–thawing physical cross-linking method, and then they were completely characterized. Two different lab-made PAA-coated iron oxide MNPs, characterized in a previous work, were prepared by coprecipitation method from two different low PAA molecular weights, Mw 1800 g/mol and 5000 g/mol. The effect of MNP content and the PAA Mw on ferrogel final properties was determined. In addition, adsorption of methylene blue (MB) and cadmium (Cd+2) was carried out to analyze the possible application of the developed materials as environmental remediation devices. The capture of a ferrogel by an external field occurs due to the force that the field gradient exerts on single magnetic particles, which is then transferred onto the polymer matrix. This force was measured as a function of the distance to a permanent magnet, and the condition to magnetically recover the sample was established. The results obtained demonstrated that the ferrogels presented in this work are able to adsorb heavy metals and then be magnetically separated.

Effect of Polyacrylic Acid on Rheology of Cement Paste Plasticized by Polycarboxylate Superplasticizer.

Viscosity-enhancing agents (VEA) have been widely employed in high flowability cement-based materials, so as to ensure that no bleeding and segregation would occur. However, in most cases, interaction between VEA and superplasticizer would be unavoidable. In this study, the effect of polyacrylic acid (PAA), known as one of the most commonly used VEAs, on rheology performance of cement paste containing polycarboxylate superplasticizer (PCE), was studied. The initial fluidity was assessed with mini slump, and rheological behavior of cement paste was evaluated with rotor rheometer. Adsorption amount was examined with total organic carbon (TOC) analyzer, and the zeta potential was also tested. The interaction between PAA and PCE in the presence of calcium ion (Ca2+) was analyzed with conductivity, X-ray photoelectron spectroscope (XPS), and dynamic light scattering (DLS). The results illustrate that PAA can adsorb onto the surface of cement particles to plasticize cement paste, being similar to PCE. In the presence of Ca2+, PAA can be curled and crosslinked, as a result of the combination between carboxyl groups (COO−) and Ca2+, thereby affecting the adsorption performance and conformation behavior. It is interesting that negative impact of PAA on dispersion efficiency of PCE can be demonstrated; one reason is the reduced adsorption amount of PCE by PAA competitively adsorbing onto the cement surface, and another possible reason is the invalided PCE by adsorption of PAA. Additionally, molecular weight of PAA should be considered if being used as VEA in PCE system.

Polyacrylic acid-coated iron oxide magnetic nanoparticles: The polymer molecular weight influence

Magnetic nanoparticles (MNPs), in particular, magnetic iron oxide-based nanoparticles were found to be useful as catalysts and as devices for data storage, environmental remediation and several biomedical applications, due to their excellent properties, such as biocompatibility and high magnetic moment. Polyacrylic acid (PAA) is a weak polyelectrolyte that can be used to stabilize the MNPs. To the best of our knowledge, the influence of PAA molecular weight and PAA concentration over the magnetic and structural properties of iron oxide nanoparticles has not been previously reported. The aim of this paper is to describe the differences evidenced in the properties of different magnetic materials by using PAA for iron oxides stabilization by one-pot coprecipitation synthesis. Iron oxide-based magnetic nanoparticles stabilized by polyacrylic acid (PAA) polymers were efficiently prepared and exhaustively characterized. The influence on the employment of two different low PAA molecular weights, Mw 1800 g/mol and 5000 g/mol, in three different iron salts: PAA ratios was analyzed. In summary, the main results showed that: for a certain PAA reactor feed higher oligomer quantities are present in MNPs as higher is the involved molecular weight of the polymeric chain; when molecular weight raises the contribution of loops and tails also does it, allowing having higher polymer contents. For both PAA’s Mw employed as the adsorbed PAA increases particles hydrodynamic diameters decreases, and their distribution becomes narrower; the PAA adsorbs onto iron oxides by chemisorption (the most probable interaction is the bidentate bridging). For the studied cases z potential values depend much more on the PAA’s quantity adsorbed onto the iron oxides than on the PAA’s Mw. MNPs are superparamagnetic and choosing the right shape of particle distribution is not central for getting estimates of the magnetization saturation, the average particle diameter and its standard deviation, while better fits are found with Normal and Log-Normal particle size distributions.

A spectroscopic approach to probe macromolecular conformational changes at interface under different environmental conditions: A case study with PAA adsorbed at oil-water Interface

Knowledge of the behavior of adsorbed macromolecules at liquid-liquid interface under different physio-chemical conditions is extremely important in different scientific disciplines such as colloidal formulations, food, cosmetic materials, drug delivery systems, anti-bacterial surfaces etc. The conformational changes of a weak polyelectrolyte, polyacrylic acid (PAA), adsorbed at a magnetically controllable oil-water interface under different local environmental condition is manifested from the Bragg peak shifts in the reflected light, after the droplets are assembled into a periodic 1D array with the aid of a weak magnetic field. The change in Bragg peak wavelength was large when the adsorbed PAA molecular weight was high. Further, the conformational changes are also confirmed from force-distance and light scattering measurements. The intermolecular force measurement shows that the adsorbed PAA undergoes a reversible conformational change from a compact globule at pH~3 to an extended structure at pH~11, with a huge change in the interdroplet spacing due to an enhanced ionization of surface groups. With further increase in pH, the extended PAA is fully collapsed due to counter-ion condensation, resulting in an irreversible aggregation. The force and light scattering measurements further confirm the conformational change from globule to extended transition. This new spectroscopic approach offers promising applications in probing macromolecular conformation at interfaces and to obtain new insight into colloidal stability.

Preparation of superparamagnetic and flexible γ-Fe2O3 nanowire arrays in an anodic aluminum oxide template

Superparamagnetic and flexible Fe2O3 nanowire arrays were fabricated by the controlled electrostatic assembly of iron oxide nanoparticles and poly(dimethyldiallylammonium chloride) (PDADMAC) in an anodic aluminum oxide (AAO) template. The micrograph of iron oxide nanowire arrays was characterized by field emission scanning electron microscopy. The magnetic hysteresis loops obtained by a vibrating sample magnetometer confirm that the nanowire arrays have superparamagnetic properties. The filling ratio of iron oxide nanoparticles and polymers in the AAO template was affected by four factors, including the concentration of iron oxide nanoparticles, the pore diameter of the AAO template, the charge ratio of iron oxide nanoparticles and PDADMAC, and the molecular weight of polyacrylic acid. The effect of the AAO template on the diameter and length of the nanowire arrays was also analyzed. In addition, the nanowire arrays were shown to be flexible because of the presence of polymers. These nanowire arrays with superparamagnetic and flexural properties have potential applications in sensor probes.

Kinetics study of acrylic acid polymerization with a microreactor platform

A microreactor platform with easily assembled reaction tubes is developed to study the kinetics of acrylic acid polymerization in aqueous solutions. In this platform, two micromixers are used to start and terminate the polymerization reaction, and several coiled reaction tubes embedded in water baths control the residence time. Operated at a total flow rate greater than 40mL/min, the reaction is independent of the monomer and initiator mixing. Experimental data showed that the orders of acrylic acid and potassium persulfate were 1.5 and 0.5, respectively, with an activation energy of 67.4kJ/mol, which is in accord with the classical kinetic mode reported in the literature. The molecular weight of polyacrylic acid (1.03×105–1.76×105) also indicated that the microreactor platform works well with macromolecules. Therefore, this technique will expand the viable methods applicable for kinetic studies.

Preparation of hydrophilic polysulfone membrane using polyacrylic acid with polyvinyl pyrrolidone

ABSTRACTThis study examined the consequences of the addition of polyvinyl pyrrolidone (PVP) of different molecular weights with constant molecular weight of polyacrylic acid (PAA) on the morphology and permeation properties of polysulfone (PSF) membranes. The asymmetric polymeric membranes were prepared by phase inversion process using PSF in N‐methyl‐2‐pyrrolidone (NMP) as a solvent. The surface structure and morphology of the prepared membranes were analyzed by field‐emission scanning electron microscope (FESEM) and atomic force microscopy (AFM). The pore number, average pore size and area of pores for all the membranes were determined by permeability method. These ultrafiltration membranes were subjected to characterizations such as measurement of pure water flux (PWF), compaction factor (CF), bovine serum albumin (BSA) rejection for finding the permeability performance, whereas equilibrium water content, contact angle, porosity, hydraulic resistance, and ion exchange capacity (IEC) are measured for evaluating the hydrophilicity. Results demonstrate that the flux performance of the membranes and morphological parameters own a crucial inter‐relationship with the molecular weight of PVP. The membrane pore area and pore number were found to be increased by increasing molecular weight of PVP with constant molecular weight of PAA. A detailed comparative study was done with Chakrabarty et al. (J. Membr. Sci. 2008, 309, 209) and found better in almost all the aspects. All the resulting parameters were compared and concluded with the fact that addition of small amount of PAA in PSF/PVP/NMP casting solution can be better than addition of PVP alone. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015, 132, 41964.

Precipitation of biomimetic fluorhydroxyapatite/polyacrylic acid nanostructures

Ordered structures of fluorhydroxyapatite (FHA) nanoparticles that resemble the nanostructure of natural human enamel have been prepared. Wet precipitation in the presence of polyacrylic acid (PAA) was used, and the particle morphology was altered by varying several reaction conditions. High molecular weight PAA increased particle length from around 54nm to several hundred nanometres, while maintaining particle width at 15nm. PAA concentration and the order of mixing the reactants also influenced crystal morphology. Optimum conditions produced dense, aligned bundles of highly elongated nanorods, which are very similar to the hierarchical nanostructure of human tooth enamel.