PAA Content Research Articles

Elaboration, characterization and application of polysulfone and polyacrylic acid blends as ultrafiltration membranes for removal of some heavy metals from water

Polysulfone (PSf)/polyacrylic acid ultrafiltration (PSf/PAA) membranes were prepared from a polymer blend in dimethylformamide by coagulation in water according to the wet phase inversion method. Immobilization of water-soluble PAA within the non-soluble PSf matrix was proven by the increase of ion exchange capacity and the intensity of the carboxyl groups’ peak with the increase of PAA content as shown by Fourier transform infrared spectra. These results lead to consider that PSf and PAA form a semi-interpenetrating polymer networks. The obtained membranes showed a decrease of mean surface-pore sizes, the overall porosity and the hydraulic permeability with the increase in PAA content. Such results were imputed to the morphologic modifications of PSf film with the immobilization of increasing PAA amount. PSf/PAA membranes showed high lead, cadmium and chromium rejection which reaches 100% at pH superior to 5.7 and a low rejection at low pH. Moreover, the heavy metal rejection decreases with feed solution concentration and applied pressure increases. These behaviors were attributed to the role of carboxylic groups in ion exchange or complexation. As a matter of fact, the strong lead ion–PAA interactions were revealed by the scanning electron microscopy with energy dispersive X-rays (SEM-EDX).

A novel approach to raspberry-like particles for superhydrophobic materials

A new strategy was developed to prepare raspberry-like particles by introducing poly(acrylic acid) (PAA)-functionalized polystyrene (PS) particles into hydrolysis reaction of tetraethoxysilane (TEOS). The monodisperse PAA-functionalized PS particles were used as cores and nanosized silica particles were then assembled on the surface of PS particles to construct raspberry-like particles during the hydrolysis process. With the increase of PAA content from 11% to 20% (wt) at the surface of latexes, the diameter of the silica particles assembled at the surface of cores decreased from 124 nm to 36 nm. The structure, morphology and constitution of the PAA-functionalized PS particles and the raspberry-like particles were characterized by Fourier transform infrared spectroscopy (FT-IR), field-emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS). In addition, the particulate films were constructed by assembling these raspberry-like particles on glass substrates. After surface modification with dodecyltrichlorosilane, superhydrophobic surfaces can be obtained and the contact angle of water on the dual-sized structured surface can be adjusted by the scale ratio of the micro/nano surface structure of raspberry-like particles.

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.

Separation of dimethyl carbonate/methanol mixtures by pervaporation with poly(acrylic acid)/poly(vinyl alcohol) blend membranes

A serial of poly(acrylic acid) (PAA)/poly(vinyl alcohol) (PVA) blend membranes with different PAA/PVA ratio were prepared for separating dimethyl carbonate (DMC)/methanol (MeOH) mixtures by pervaporation. FTIR was used to determine whether there was an esterification reaction between PAA and PVA. Swelling experiments were carried out in DMC/MeOH mixtures by using different blend membranes to investigate the swelling behavior of the membranes. The blend membranes with different PAA content were used to separate DMC/MeOH azeotrope through pervaporation experiments. The effects of operation temperatures and feed composition on pervaporation performances were also investigated. The results showed that the blend membrane containing 70 wt.% PAA had a highest separation factor of 13 and a permeate flux of 577 g/(m 2 h) at 60 °C for separating DMC/MeOH azeotrope, which could be expected that the membrane prepared in this work should be used to separate DMC/MeOH mixtures in real application.

Synthesis of nanosized PAA/titania hybrid composites—Experiment and modeling

A stable colloid of nanosized PAA/titania hybrid has been successfully prepared, in which chelating bond was evidenced by FTIR spectra. Moreover, TGA curves indicated the degree of chelation to be increased with an increase of PAA content. SEM micrographs demonstrated that the size of hybrid aggregates would be smaller at increased ratio of PAA to titania, because the higher amount of PAA would decrease the degree of aggregation and inhibit the titania growth. A new sol–gel kinetic model for partially chelated titanium alkoxide by PAA has been proposed to simulate the experimental results. Based on this sol–gel kinetic model which takes into account the effect of chelation, the concentration of water, Ti OR, Ti OH, and (Ti O) Ti bonds during sol–gel reaction could be calculated. The variation of number of particles at different reaction times could also be shown. Finally, the size of hybrid aggregates at different degrees of chelation could be qualitatively described. The simulated results from this model were in agreement with the observation from SEM micrographs.

DEVELOPMENT OF AN INJECTABLE PH- AND TEMPERATURE-RESPONSIVE HYDROGEL DRUG DELIVERY SYSTEM.

Regions of local acidosis, such as that seen in myocardial ischemia, offer a target for stimuli-sensitive drug delivery systems. Hydrogels are polymer networks that are capable of entrapping significant amounts of water and can be designed to respond to stimuli such as temperature, pH, light, and electric fields. These properties make them highly attractive for drug delivery systems because of their biocompatibility and potential for drug targeting. In particular, reversible hydrogels are attractive because they can be designed to be soluble under normal physiologic conditions but form a gel under other conditions, such as decreased pH. In this study, we investigated the sol-gel properties of a pH- and temperature-sensitive polymer and assessed the ability of this polymer to be developed into an injectable hydrogel drug delivery system for ischemic cardiac tissue. Poly(N-isopropylacrylamide-co-propyl acrylic acid) (p(NIPAAm-co-PAA)) was synthesized by reversible addition fragmentation chain transfer (RAFT) polymerization. The feed composition of the pH-sensitive component, PAA, was varied between 0 and 20 mol%. Polymer was characterized by gel permeation chromatography and proton nuclear magnetic resonance to determine the molecular weight and polymer composition, respectively. Polymer samples were dissolved in phosphate buffer, and then pH was adjusted between 4.5 and 7.0. One-milliliter samples were loaded onto a rheometer to quantify viscoelastic properties. P(NIPAAm-co-PAA) polymers of varying PAA content were successfully synthesized by RAFT. At physiologic pH (7.4), the polymer did not form a gel but rather remained in the soluble state at all temperatures. However, at low pH (below approximately pH 5.5), with increasing temperature (in a physiologically relevant range), the polymers underwent a phase change from a clear liquid, to a cloudy liquid, and finally to a gel. As the pH was decreased further, the gelation temperature for a given polymer composition also decreased. In conclusion, by varying the relative ratio of NIPAAm and PAA in p(NIPAAm-co-PAA), the temperature and pH at which a gel forms can be controlled. Future studies will investigate the drug-release properties of this system.

Novel method for preparation of polyurethane elastomers with improved thermal stability and electrical insulating properties

AbstractA novel method was developed for the preparation of polyurethane with enhanced thermal stability and electrical insulation properties via the reaction of epoxy‐terminated polyurethane prepolymer (EPU) and poly(amic acid) (PAA). EPUs were synthesized from the reaction of glycidol with NCO‐terminated polyurethane prepolymers, which were prepared from the reaction of polycaprolactone‐based polyol (CAPA) of different molecular weights and some commercially available diisocyanates including hexamethylene diisocyante, toluene diisocyanate, and 4,4′‐methylene bis(phenyl isocyanate). PAA was prepared from the reaction of equimolar amounts of pyromellitic dianhydride and oxydianiline. The effects of PAA content, the nature of diisocyanate, and the molecular weight of CAPA on the mechanical, thermal, thermomechanical, and electrical properties of the final networks were investigated. The crosslink density of the samples was determined according to an equilibrium swelling method using the Flory–Rehner equation and was correlated to the structure of the final polymers. Gel content and activation energy of network formation in the absence and the presence of a tertiary amine catalyst were also studied. The results showed considerable improvement in the thermal, electrical, and mechanical properties compared to those of other common polyurethanes. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 1776–1785, 2007

Synthesis, thermal and structural characterization of nanocomposites for potential applications in construction

Several calcium silicate hydrate (C–S–H)-polymer nanocomposite (C–S–HPN) materials have been prepared by incorporating poly(acrylic acid) (PAA) into the inorganic layers of C–S–H during precipitation of quasicrystalline C-S-H from aqueous solution. The synthetic C–S–HPN materials were characterized by X-ray fluorescence (XRF), X-ray diffraction (XRD), Fourier-transform infrared (FTIR) spectroscopy, scanning electron microscopy/energy dispersive spectroscopy (SEM-EDS), thermogravimetry (TG), differential thermogravimetry (DTG) and differential scanning calorimetry (DSC). The XRD peaks of C–S–HPN materials suggest the intermediate organizations presenting both intercalation of PAA and exfoliation of C–S–H. The SEM images of C–S–H and C–S–HPN materials with different PAA contents exhibit the significant differences in their morphologies. Effects of the material compositions on the thermal stability of series of C–S–HPN materials along with PAA and C–S–H has been studied by TG, DTG and DSC. Three significant decomposition temperature ranges were observed on the TG curves of all C–S–HPN materials.

Preparation, thermal, spectral and microscopic studies of calcium silicate hydrate–poly(acrylic acid) nanocomposite materials

A series of calcium silicate hydrate (C–S–H)-polymer nanocomposite (C–S–HPN) materials were prepared by incorporating poly(acrylic acid) (PAA) into the inorganic layers of C–S–H during precipitation of quasicrystalline C–S–H from aqueous solution. The as-synthesized C–S–HPN materials were characterized by X-ray fluorescence (XRF), X-ray diffraction (XRD), scanning electron microscopy-energy dispersive spectroscopy (SEM-EDS), Fourier-transform infrared (FTIR) spectroscopy, thermogravimetric analysis (TG) and differential scanning calorimetry (DSC). The XRD analysis of C–S–HPN materials suggest the intermediate organizations presenting intercalation of PAA within C–S–H and exfoliation of C–S–H. The SEM micrographs of C–S–H, PAA and C–S–HPN materials with different PAA contents exhibit the significant differences in their morphologies. The effect of the material’s composition on the thermal stability of a series of C–S–HPN materials along with PAA and C–S–H were studied by TG, DTA and DSC. Three significant decomposition temperature ranges were observed on the TG curves of all C–S–HPN materials.

Preparation, characterization and in vitro drug release properties of polytrimethylene carbonate/polyadipic anhydride blend microspheres

AbstractPolyadipic anhydride (PAA), an aliphatic polyanhydride, and polytrimethylene carbonate (PTMC), an aliphatic polycarbonate, were synthesized via ring opening polymerization of oxepan‐2,7‐dione and melt‐condensation of trimethylene carbonate (1,3 dioxan‐2‐one), respectively. PTMC–PAA blend microspheres containing different ratios of buprenorphine HCl (2, 5, and 10%) were prepared by an oil‐in‐oil emulsion solvent removal method. Microspheres with different ratios of PTMC–PAA (85/15, 70/30, and 55/45) containing 5% buprenorphine HCl were prepared. Microspheres were spherical with visible cracks and pores on the surface. The average particle size of microspheres was around 200 μm for all microspheres. Drug loading efficiency of PTMC–PAA microspheres (85/15, 70/30, and 55/45) was 97.2, 95.2, and 70.2%, respectively. With the increase in the PTMC ratio, the melting point and the enthalpy of melting were both decreased. The mechanism for drug release from PTMC–PAA blend microspheres were generally a combination of drug diffusion through polymers and biodegradation of the polymers. In first three days, the release from microspheres followed zero order kinetics and was dependent on the PAA content. After three days the drug release from microspheres followed first order kinetics. In conclusion it was demonstrated that buprenorphine HCl release from microspheres could be successfully controlled by using different ratios of PTMC–PAA blends. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 2377–2383, 2006

Bioartificial materials based on blends of dextran and poly(vinyl alcohol- co-acrylic acid)

Bioartificial polymeric materials based on blends of dextran and poly(vinyl alcohol- co-acrylic acid) P(VA- co-AA) were prepared in the form of films and characterised to evaluate the miscibility of the natural component with the synthetic one. The idea of this work was to compatibilise PVA and dextran by introducing carboxylic groups along the PVA chains. The copolymer was synthesised and characterised in our laboratories. The results evidenced that the copolymer had an appropriate molecular weight and the content of PAA in the copolymer was 45% (weight). Then, films with different composition ratios were prepared by solution casting and analysed by differential scanning calorimetry (DSC), scanning electron microscopy (SEM), infrared spectroscopy (FT-IR), thermogravimetric analysis (TGA), chemical imaging analysis and mechanical tests. The results obtained indicated that the introduction of carboxylic groups along the PVA chains had a positive effect on the miscibility degree of the synthetic component with the biological one.

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™).

In vitro mineralization of gelatin-polyacrylic acid complex matrices

Gelatin-polyacrylic acid (gel-PAA) matrices were obtained by slow diffusion of polyacrylic acid into gelatin gels. The matrices were submitted to uniaxial stretching, which induces a preferential orientation of the collagen molecules, and used as biomimetic substrates for the nucleation of hydroxyapatite from simulated body fluid (SBF). The relative amount of hydroxyapatite deposited from 1.5SBF increases as a function of polyelectrolyte content in the matrices, up to about 30 wt%. In the absence of PAA, the inorganic phase is laid down on the surface of the gelatin matrices as hemispherical aggregates. At variance, hydroxyapatite deposition in the gel-PAA composite matrices at relatively low PAA content occurs preferentially in the spaces between the layers on the surface of the matrices and displays a tablet-like morphology. At high polyelectrolyte concentration, an almost uniform layer of hydroxyapatite covers the whole surface of the matrices. The preferential orientation of the (002) hydroxyapatite reflection indicates a close relationship between the inorganic crystals and the collagen molecules.

Pervaporation of MTBE/methanol mixtures through PVA membranes

Sorption and pervaporation experiments were carried outwith PVA/PAA cross-linked membranes for the separation of azeotropic methyl tert-butyl ether and methanol mixtures. The influence of the PVA/PAA ratio and liquid mixture composition were investigated. With increasing PAA content in the membranes, solubilities and fluxes decreased and selectivities increased. Total sorption and fluxes increased with increasing concentration of McOH. Increasing the concentration of McOH resulted in decreasing selectivities. Because of polarity, McOH permeated selectively through the membranes. Sorption results showed the same tendency with pervaporation results.

Spin label study of phase morphology and polymer segmental motion in poly(acrylic acid)–poly(ethylene oxide) complex

AbstractThe ESR lineshapes of nitroxide radical end‐labeled on poly(ethylene oxide) (SLPEO) for the pure polymer and for different weight ratio complexes with poly(acrylic acid) (PAA) were studied as a function of temperature. For SLPEO one spectral component was detected in the entire temperature range, indicating that the spin label was in the homogeneous phase domain. For all PAA–PEO complexes two spectral components with different rates of motion, a ‘fast’ and a ‘slow’ component, were observed, which indicates the existence of microheterogeneity at the molecular level: the more mobile the PEO‐rich microphase, the more rigid is the PAA‐rich microphase. On the other hand, the SLPEO polymer segmental motion was restricted owing to the hydrogen bond interaction between the carboxyl proton in PAA and the ether oxygen in PEO. This restriction was exacerbated with increasing the PAA content in the complex, which could be further substantiated through the calculated S and τc values. Copyright © 2003 John Wiley & Sons, Ltd.

Drug Delivery Systems Based on Porous Chitosan/Polyacrylic acid Microspheres

AbstractPorous microspheres have been prepared by suspension free radical polymerization of acrylic acid (AA) in the presence of chitosan (CHI). The microspheres were characterized by FTIR and environmental SEM. The PAA content of the microspheres was estimated to be in the range 45–50 wt.‐%. The swelling degree of these particles is almost constant in the range 2 < pH < 5, but it increases considerably as the pH is raised from 5 to 10. The release profiles of microspheres loaded with meclofenamic acid (MF) were determined at pH 2, 7.4, and 10. The in vitro release of MF at different pHs was modulated by the solubility of the drug. These microcapsules are biodegradable and presented good biocompatibility and biodegradability during in vivo experiments.ESEM microphotograph of the porous PAA/CHI microspheres.magnified imageESEM microphotograph of the porous PAA/CHI microspheres.

Nitroxide spin probe study of probe size, hydrogen bonding and polymer matrix rigidity effects on poly(acrylic acid)/poly(ethylene oxide) complexes

AbstractAn electron spin resonance (ESR) spin probe study was performed on 1 : 1 by weight poly(acrylic acid) (PAA)/poly(ethylene oxide) (PEO) complex over the 100–450 K temperature range with a series of tetramethylpiperidyloxy‐based spin probes. Measurements of the parameters T5mT, Ta and Td demonstrated the effects of probe size and the strength of hydrogen bonding. The probes in the series Tempone, Tempo, Tempol and Tamine (respectively 4‐oxo‐, unsubstituted, 4‐hydroxy‐ and 4‐amino‐2,2,6,6,‐tetramethylpiperidine ‐1‐oxyl) displayed noticeable increases in the hydrogen‐bonding effect, as indicated by Ta and Td. These increases correlated with increasing hydrogen bond acceptor strength. On the other hand, as the probe size became larger, T5mT gradually increased due to the free volume decrease. These effects were analyzed using the established theoretical relationship of T5mT to probe volume expressed by f. Meanwhile, in order to investigate the effect of polymer matrix rigidity, a similar study was performed with a nitroxide spin probe, 2,2,6,6‐tetramethyl‐1‐piperidine‐1‐oxyl (Tempo), on PAA/PEO complexes of different weight compositions. The quantitative fast motion fraction in the composite ESR spectrum was calculated. The influence of changes in the composition of PAA on the molecular mobility was characterized by changes of the spectral parameters $2A^{'}_{zz}$ and τc. The molecular mobility was shown to diminish with increasing content of PAA in PAA/PEO blends duo to the restriction of the polymer matrix rigidity increase. Copyright © 2003 John Wiley & Sons, Ltd.