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Query: UMLS:C0267964 (PAA)
 2,561 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

A cationic, high-water-content hydrogel membrane composed of poly(vinyl alcohol) (PVA) and poly(ally-biguanido-co-allylamine) hydrochloride (PAB) with positively charged biguanido groups that resemble arginine residues was developed. The PAB was prepared by reacting poly(allylamine) hydrochloride (PAA) with guanyl-O-methyl isourea. PAB/PVA hydrogel membranes were prepared by repeated freezing and thawing. For comparison, hydrogel membranes composed of PAA and PVA were also prepared. The interaction between these hydrogel membranes and mouse fibroblast (L929) was studied by a cell culture method. The PAB hydrogel blend had a relatively low percentage of initial cell attachment. The cell growth on the PAB hydrogel membranes showed a maximum at 5 mol % PAB content that was as high as commercially available plastic films. However, cells on hydrogel membranes with 50 mol % PAB content and 0 mol % PAB content (only PVA) did not seem to grow; neither did the 5/95 PAA/PVA membranes. Water contact angles of hydrogel membranes did not vary with the PAB content. Morphology of the cell attachment was observed by SEM. On the PAB blend hydrogel surfaces, cells were not spindle-shaped and monolayers, but rather cells aggregated in spherical clusters.
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PMID:Cell growth on poly(vinyl alcohol) hydrogel membranes containing biguanido groups. 800 50

Polyterephthalamide microcapsules containing a poly(acrylic acid) gel as a macromolecular ligand (PAA-CAPS) were prepared using an original two step polymerization process in a water-in-oil inverse emulsion system. A polyamide microcapsule containing acrylic acid, initiator and cross-linking agent, is formed by interfacial polycondensation of terephthaloyl dichloride with hexamethylenediamine. In situ radical polymerization of the microcapsule core acrylic acid is initiated to obtain encapsulated poly(acrylic acid) gel. Reference polyamide microcapsules, i.e. without ligand (CAPS), were also synthesized. The mean diameter of synthesized microcapsules was 210 microm, and the microcapsule wall thickness was evaluated by SEM and TEM observations of microcapsule cross-section cuts. The microcapsule water content was determined by thermogravimetric experiments. The extractabilities of Cu(II), Ni(II), Co(II) and Zn(II) into PAA-CAPS were examined. The stripping of the various cations can be promoted in diluted hydrochloric acid solutions.
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PMID:Extraction of metal cations by polyterephthalamide microcapsules containing a poly(acrylic acid) gel. 1181 55

The effect of pH on the complexation of poly(acrylic acid) with poly(vinyl alcohol) in aqueous solution, the miscibility of these polymers in the solid state and the possibility for crosslinking the blends using gamma radiation has been studied. It is demonstrated that the complexation ability of poly(vinyl alcohol) with respect to poly(acrylic acid) is relatively low in comparison with some other synthetic non-ionic polymers. The precipitation of interpolymer complexes was observed below the critical pH of complexation (pH(crit1)), which characterizes the transition between a compact hydrophobic polycomplex and an extended hydrophilic interpolymer associate. Films prepared by casting from aqueous solutions at different pH values exhibited a transition from miscibility to immiscibility at a certain critical pH, pH(crit2), above which hydrogen bonding is prevented. It is shown here that gamma radiation crosslinking of solid blends is efficient and only results in the formation of hydrogel films for blends prepared between pH(crit1) and pH(crit2). The yield of the gel fraction and the swelling properties of the films depended on the absorbed radiation dose and the polymer ratio. [Diagram: see text] SEM image of an equimolar PAA-PVA blend cast from a pH 4.6 solution.
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PMID:pH effects on the complexation, miscibility and radiation-induced crosslinking in poly(acrylic acid)-poly(vinyl alcohol) blends. 1588 88

The purpose of this study was to develop an oral thiomer-based microparticulate delivery system for insulin by ionic gelation. The microparticulate matrix consisted of either poly(acrylic acid)-cysteine (PAA-Cys) and alginate-cysteine (Alg-Cys) or the corresponding unmodified polymers (PAA, Alg). Two different viscosities of alginates were provided for the study, low and medium. Three different types of microparticles were prepared via ionic gelation with calcium (Alg, AlgPAA and AlgPAA-Cys) and their different properties evaluated in-vitro (particle size and shape, drug loading and release profile, swelling and stability). The mean particle size of all formulations ranged from 400 to 600 microm, revealing the lowest for thiolated microparticles. SEM micrographs showed different morphological profiles for the three different types of microparticles. Encapsulation efficiency of insulin increased within the following rank order: Alg (15%) < AlgPAA (40%) < AlgPAA-Cys (65%). Alginate and AlgPAA microparticles displayed a burst release after 30 min, whereas the thiolated particles achieved a controlled release of insulin over 3 h. The swelling ratio was pH dependent: in simulated intestinal fluid microparticles exhibited a much higher water uptake compared with simulated gastric fluid. Due to the formation of intraparticulate disulfide bonds during the preparation process, thiolated particles revealed a higher stability. It was also observed that the viscosity of the two alginates used had no influence on the properties of the particles. According to these results AlgPAA-Cys microparticles obtained by ionic gelation and stabilized via disulfide bonds might be an alternative tool for the oral administration of therapeutic peptides.
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PMID:Oral peptide delivery: in-vitro evaluation of thiolated alginate/poly(acrylic acid) microparticles. 1788 89

A biocomposite of hydroxyapatite (HAp) with electrospun nanofibrous scaffolds was prepared by using chitosan/polyvinyl alcohol (CS/PVA) and N-carboxyethyl chitosan/PVA (CECS/PVA) electrospun membranes as organic matrix, and HAp was formed in supersaturated CaCl2 and KH2PO4 solution. The influences of carboxylic acid groups in CECS/PVA fibrous scaffold and polyanionic additive poly(acrylic acid) (PAA) in the incubation solution on the crystal distribution of the HAp were investigated. Field-emission scanning electron microscopy (FE-SEM), energy-dispersive spectroscopy (EDS), wide-angle X-ray diffraction (WAXD), and Fourier transform infrared (FTIR) were used to characterize the morphology and structure of the deposited mineral phase on the scaffolds. It was found that addition of PAA to the mineral solution and use of matrix with carboxylic acid groups promoted mineral growth and distribution of HAp. MTT testing and SEM imaging from mouse fibroblast (L929) cell culture revealed the attachment and growth of mouse fibroblast on the surface of biocomposite scaffold, and that the cell morphology and viability were satisfactory for the composite to be used in bioapplications.
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PMID:In situ mineralization of hydroxyapatite on electrospun chitosan-based nanofibrous scaffolds. 1832 11

Double-surface-silvered polyimide films have been successfully fabricated using silver ammonia complex cation ([Ag(NH3)2]+) as the silver precursor and 3,3',4,4'-benzophenonetetracarboxylic dianhydride/4,4'-oxidianile- (BTDA/ODA-) based poly(amic acid) (PAA) as the polyimide precursor via a direct ion-exchange self-metallization technique. The process has been clarified to involve the loading of silver(I) into PAA via ion exchange, the thermally induced reduction of silver(I) to silver(0) and the concomitant imidization of PAA to polyimide upon thermal treatment, the subsequent silver-catalyzed and oxygen-assisted decomposition of the polyimide overlayer, and the self-accelerated aggregation of silver clusters on the film surface to produce well-defined surface silver layers. By employing [Ag(NH3)2]+ solution with a concentration of only 0.01 M and an ion-exchange time of no more than 10 min, the controlled formation of highly reflective and conductive silver surfaces upon thermal treatment at 300 degrees C for less than 4.5 h indicates that the present work provides an efficient route and an effacious silver species for polyimide surface metallization. Although the alkaline characteristics of [Ag(NH3)2]+ have a strong hydrolysis effect on the polyimide precursor chains, the final metallized films retain the key mechanical and thermal properties of the pure polyimide. Films were characterized by ATR-FTIR, XPS, ICP-AES, SEM, TEM, DSC, TGA, reflectivity, conductivity, and mechanical measurements.
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PMID:Controlled formation of optically reflective and electrically conductive silvered surfaces on polyimide film via a direct ion-exchange self-metallization technique using silver ammonia complex cation as the precursor. 1840 10

Maleimide groups are synthesized on the surface of PE films by means of two different routes, from oxidized and anhydride-grafted PE films. Maleimide groups covalently bonded to the surface of PE film were used as photopolymerization initiators of acrylic acid (AA) and glycidyl methacrylate (GMA). The formation of poly (acrylic acid) (PAA) and poly (glycidyl methacrylate) (PGMA) covalently bonded to the modified PE film surface by the photopolymerization process was demonstrated by ATR-FTIR, gravimetry, and SEM results. The thickness of the polymer layers formed in the polymerization depends on the irradiation time. The PAA layer formed in the polymerization is thinner than 250 nm, whereas that of PGMA in some case is thicker than 3 mum.
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PMID:Maleimide immobilized on a PE surface: preparation, characterization and application as a free-radical photoinitiator. 1909 63

Currently, research is focused on the synthesis of new composite coagulants, which are constituted of both inorganic and organic materials. In this paper, the development of relevant reagents was investigated, by combining the inorganic pre-polymerised iron-based coagulant Polyferric Sulphate (PFS) with an organic, non-ionic polymer (Polyacrylamide, PAA) under different PAA/Fe (mg/l) and OH/Fe molar ratios. Moreover, the new reagents were characterised in terms of typical properties, stability and morphological analysis (XRD, FTIR, SEM). Their coagulation performance, when treating low or high turbid kaolin-humic acid suspensions, was also investigated, whereas the applied coagulation mechanisms were discussed by using the Photometric Dispersion Analysis (PDA) analysis. The results show that the new coagulation reagents present improved properties, including increased effective polymer species concentration, and they exhibit very good stability. The respective tests using PDA confirmed that the predominant coagulation mechanism of PFS-PAA is the bridge formation mechanism. Coagulation experiments in low or high turbid kaolin-humic acid suspensions reveal that the novel composite reagent PFS-PAA exhibits better coagulation performance, when compared with simple PFS, in terms of zeta-potential reduction, turbidity and organic matter removal and residual iron concentration.
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PMID:A new inorganic-organic composite coagulant, consisting of polyferric sulphate (PFS) and polyacrylamide (PAA). 1956 Jan 80

Interactions between phospholipid vesicles and poly(acrylic acid) (PAA) are of fundamental importance for pH-sensitive delivery systems in pharmaceutical applications. In this study, we investigated the behavior of 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC) at varied concentrations of PAA with low and high molecular weights. Differential scanning calorimetry and fluorescence microscopy experiments suggested that hydrogen bonding between the carboxyl group of PAA and the phosphodiester group of the lipid is the main driving force for association under acidic conditions. Complexation between DPPC and PAA depends on the PAA molecular weight and concentration. At high enough concentrations of the large molecular weight PAA, the polymer can completely disrupt the bilayers of DPPC. For the small molecular weight PAA, in contrast, the complexation leads to vesicle aggregation without destroying the bilayers. The difference in complex structure was detected by SEM and a UV-visible spectrophotometer. At alkaline pH, complexation did not occur because of strong dissociation of PAA.
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PMID:Interaction between poly(acrylic acid) and phospholipid vesicles: effect of pH, concentration, and molecular weight. 2029 4

A new, efficient, palladium- and chromium-free process for the electroless plating of acrylonitrile-butadiene-styrene (ABS) polymers has been developed. The process is based on the ion-exchange properties of poly(acrylic acid) (PAA) chemically grafted onto ABS via a simple and one-step method that prevents using classical surface conditioning. Hence, ABS electroless plating can be obtained in three steps, namely: (i) the grafting of PAA onto ABS, (ii) the copper Cu(0) seeding of the ABS surface, and (iii) the nickel or copper metallization using commercial-like electroless plating bath. IR, XPS, and SEM were used to characterize each step of the process, and the Cu loading was quantified by atomic absorption spectroscopy. This process successfully compares with the commercial one based on chromic acid etching and palladium-based seed layer, because the final metallic layer showed excellent adhesion with the ABS substrate.
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PMID:ABS polymer electroless plating through a one-step poly(acrylic acid) covalent grafting. 2036 51


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