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Query: UMLS:C1832588 (PSS)
 2,979 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

A new, convenient, and inexpensive approach to process and granulate titania powders by a chemical route is proposed. It is based on the use of a formulation that includes a polyanion such as poly(sodium 4-styrenesulfonate) (PSS). Such a polyelectrolyte is most often considered to achieve dispersion of oxide powders in water. Basically, it adsorbs onto the surface of particles and induces electrical and/or steric interactions between particles in the suspension, which prevents agglomeration and rapid sedimentation. The advantages of polyelectrolytes in ceramic processing is well documented in the literature to produce low viscosity suspensions that are further used to form ceramic parts. In the case of TiO2 powders, such aqueous dispersions were obtained by adding small quantities of PSS. However, when exploring the behavior of mixtures containing lower contents of dispersant, we have discovered that, well below the optimum concentration required to get stable dispersions, the polyelectrolyte can act as a binder for titania particles. This can confer cohesion to the agglomerates, which can be processed to form large size (e.g., millimeter size) spheres. This phenomenon takes place when the oxide surface carries both positive and negative electrical charges and can be explained on a simple basis involving surface chemistry. For the optimum concentration of PSS that disperses titania, a polycation such as chitosan should be added to get spheres. This simple technique is expected to receive increasing attention due its potentialities and strong advantages with respect to other granulation techniques, such as spray-drying, which are energy consuming.
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PMID:Granulating titania powder by colloidal route using polyelectrolytes. 1877 32

Water-dispersible polyelectrolyte multilayers (PEM) were obtained by layer-by-layer assembly of poly(allylamine hydrochloride) (PAH) and poly(sodium 4-styrene sulfonate) (PSS) on water-soluble poly(ethylene glycol)- graft-multiwalled carbon nanotubes (PEG- g-MWNTs), and their structures were investigated using solution (1)H NMR. It was clearly shown that some segments of the adsorbed topmost layers formed in layer-by-layer assembly processes are still highly mobile in aqueous solution, and these segments are totally compensated by subsequent coatings of the oppositely charged layers to form ionically cross-linked polyelectrolyte complexes (PEC) layers; it was demonstrated that the ionization behaviors of the highly mobile segments of the topmost PAH layers are similar to those in solution rather than those in the bulk multilayers at different pH. Furthermore, the similarity among the PEM on substrates and the PEC colloids prepared under similar conditions in solution was supported by solution (1)H NMR results, and the unequal stiochiometry of the cationic group from PAH and the anionic group from PSS in the cores of the PEC colloids in solution was identified from solution (1)H NMR results using PEG as external references. On the basis of these, it is suggested that the PEC layers in PEM formed from coating of the adsorbed topmost PAH layers with PSS solution contain excess PSS, and reversely those formed from coating of the adsorbed topmost PSS layers with PAH solution contain excess PAH. Hence a new description of PEM is put forward that the polyelectrolyte multilayers are composed of alternate layers excess either in PSS or in PAH.
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PMID:Finer structures of polyelectrolyte multilayers reflected by solution (1)H NMR. 1881 32

In this work we build on prior studies of the novel water-soluble cationic conjugated polymer known as "P2" (poly{2,5-bis[3-( N, N, N-triethylammonium bromide)-1-oxapropyl]-1,4-phenylenevinylene}) with a focus on its incorporation into thin films for such applications as photovoltaics or electroluminescent devices. Multilayer assemblies were constructed using P2, the anionic surfactant sodium dodecyl sulfate (SDS), and the polyanion poly(sodium 4-styrene-sulfonate) (PSS) using the technique of layer-by-layer electrostatic self-assembly (LBL-ESA). SDS was observed to affect the layer thicknesses and absorbance characteristics of the films. We show that the optical properties and photo-oxidative resistance can be improved by varying the SDS content in the assemblies. Specifically, the surfactant-complexed poly( p-phenylenevinylene) (PPV) shows an enhanced absorption at longer wavelengths as well as improved photostability. Therefore, our work may have broad implications on the development of stable PPV-based materials in general and their efficient integration into thin films technologies.
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PMID:Controlling layer thickness and photostability of water-soluble cationic poly(p-phenylenevinylene) in multilayer thin films by surfactant complexation. 1894 65

Heterojunction of hydrophobic poly(1,4-phenylenevinylene) (PPV) on hydrophilic CdS nanoparticles was successfully prepared by the multi-layering of poly(p-xylene tetrahydrothiophenium chloride) (pre-PPV: precursor of PPV polymer) and poly(3,4-ethylenedioxythiophene)/poly(styrene sulfonate) (PEDOT:PSS) in an aqueous solution followed by a thermal treatment. CdS nanoparticles thin films were prepared on tin-doped indium oxide (ITO) by a chemical-bath-deposition method. The CdS surface was hydrophilic with low water contact angle of 15 degrees. Positively charged and water-soluble pre-PPV was used to form multilayers with PEDOT:PSS by a layer-by-layer deposition method. Pre-PPV is easily converted to conjugated PPV polymer by a thermal treatment. The CdS nanoparticles-(PPV/PEDOT:PSS) multilayer films constitute efficient acceptor-sensitizer dyad systems, which generate a photocurrent of 2,660 nA/cm2 under the air mass (AM) 1.5 conditions (I=100 mW/cm2) for sample with 4.5 bilayers.
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PMID:Heterojunction of hydrophobic poly(1,4-phenylenevinylene) and hydrophilic PEDOT:PSS on hydrophilic CdS nanoparticles. 1904 96

Sum-Frequency Vibrational Spectroscopy (SFVS) has been used to investigate the effect of nitrogen-flow drying on the molecular ordering of Layer-by-Layer (LbL) films of poly(allylamine hydrochloride) (PAH) alternated with poly(styrene sulfonate) (PSS). We find that films dried by spontaneous water evaporation are more ordered and homogeneous than films dried by nitrogen flow. The latter are quite inhomogeneous and may have regions with highly disordered polymer conformation. We propose that drying by spontaneous water evaporation reduces the effect of drag by the drying front, while during nitrogen-flow drying the fast evaporation of water "freezes" the disordered conformation of adsorbed polyelectrolyte molecules. These findings are important for many applications of LbL films, since device performance usually depends on film morphology and its molecular structure.
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PMID:Molecular ordering in layer-by-layer polyelectrolyte films studied by sum-frequency vibrational spectroscopy: the effects of drying procedures. 1905 86

Compression of the polyelectrolyte multilayers has been found previously when they were pressed by a poly(dimethylsiloxane) (PDMS) stamp under a small pressure (Macromolecules 2004, 37, 8836). In this work, we further found that the pattern formation of the poly(diallyldimethylammonium chloride) (PDADMAC) containing multilayers is dependent on the drying time of the multilayers prior to compression. After the poly(4-styrenesulfonic acid-co-maleic acid) sodium salt (PSSMA)/PDADMAC multilayers were dried at 70% relative humidity and room temperature for 2, 6, and 12 h, compression of the multilayers by a PDMS stamp with linear patterns obtained double strips, high ridges and linear patterns on the multilayers, respectively. These phenomena were independent of the layer number and salt concentration and could be applied to other PDADMAC containing multilayer systems such as poly(styrene sulfonate) sodium salt (PSS)/PDADMAC and poly(acrylic acid, sodium salt) (PAA)/PDADMAC. A model was suggested to depict the process, and the influence of the water content on the multilayer structure and properties was discussed. The stability experiments revealed that the strips and high ridges obtained at shorter drying time could be erased by incubation in water for 5 h, while the compression created patterns were very stable.
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PMID:Influence of drying time of polyelectrolyte multilayers on the compression-induced pattern formation. 1905 63

Polystyrene sulfonate (PSS 77 kDa) adsorbed onto oppositely charged dioctadecyldimethylammonium bromide (DODA) monolayers at the air/water interface is investigated with X-ray reflectivity and grazing incidence diffraction. The alkyl tails of DODA in the condensed phase form an oblique lattice with large tilts and intermediate azimuth angle. On PSS adsorption, the alkyl tail structure is maintained; only the tilt angle changes. Bragg peaks caused by flatly adsorbed, aligned PSS chains are observed, when DODA is in the fluid and also when it is in the condensed phase. The two-dimensional lamellar phase is only found at intermediate PSS bulk concentrations (0.001-1 mmol/L). In this phase, the PSS coverage can be varied by a factor of 3, depending on DODA molecular area and polymer bulk concentration. Charge compensation in the lamellar phase is almost achieved at 1 mmol/L. At larger bulk concentrations, PSS adsorbs flatly yet without chain alignment. Presumably, a necessary condition for a two-dimensional lamellar phase is a pronounced electrostatic force which causes a large persistence length as well as repulsion between the aligned chains.
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PMID:Two-dimensional lamellar phase of poly(styrene sulfonate) adsorbed onto an oppositely charged lipid monolayer. 1912 2

Models currently used have been developed to describe the storage response in the activated sludge process. In these models the distribution of the substrate flux between growth and storage is an empirical function. rRNA-structured biomass models are proposed to describe the metabolic status of cells in view of predicting the growth response (dmicro/dt) of cells in activated sludge process. The autocatalytic reaction rate of the synthesis of the PSS component (rRNA) can provide a mechanistic explanation for the growth response and the growth lag phase. The proposed models were able to describe and predict properly the growth response of the biomass in various types of reactor. Such models could be more widely applicable by using intrinsic model parameters. This would be a key improvement for as it would lead to improved models for design.
Water Sci Technol 2009
PMID:Modelling using rRNA-structured biomass models. 1923 60

The electrical transport and chemical sensing properties of individual multisegmented Au-poly(3,4-ethylenedioxythiophene)(PEDOT)-Au nanowires have been investigated. Temperature dependent conductivity measurements show that different charge transport mechanisms influence these properties in two types of PEDOT nanowires. Charge transport in PEDOT/poly(4-styrenesulfonic acid) (PSS) nanowires is in the insulating regime of the metal-insulator transition and dominated by hopping, while PEDOT/perchlorate (CIO4) nanowires are slightly on the metallic side of the critical regime. The vapor sensing properties of individual nanowires to water and methanol reflect the fact that the two kinds of PEDOT nanowires operate in different transport regimes. Nanowires in the metallic transport regime show much greater sensitivity to vapor-phase analytes than those in which transport is dominated by hopping.
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PMID:Electrical transport and chemical sensing properties of individual conducting polymer nanowires. 1936 7

The formation of complexes with stoichiometric (1:1) as well as nonstoichiometric (2:1) and (1:2) compositions between oppositely charged synthetic polyelectrolytes carrying strong ionic groups and significantly different molecular weights is reported in this contribution. Poly(sodium styrenesulfonate) (NaPSS) was used as polyanion, and a range of copolymers with various molar ratios of the poly(methacryloxyethyltrimethylammonium) chloride, poly(METAC), and the nonionic poly(ethylene oxide) ether methacrylate, poly(PEO45MEMA), were used as polycations. Formation and stability of PECs have been investigated by dynamic and static light scattering (LS), turbidity, and electrophoretic mobility measurements as a function of polyelectrolyte solution concentration, charge density of the cationic polyelectrolyte, and mixing ratio. The data obtained demonstrate that in the absence of PEO45 side chains the 100% charged polymer (polyMETAC) formed insoluble PECs with PSS that precipitate from solution when exact stoichiometry is achieved. In nonstoichiometric complexes (1:2) and (2:1) large colloidally stable aggregates were formed. The presence of even a relatively small amount of PEO45 side chains (25%) in the cationic copolymer was sufficient for preventing precipitation of the formed stoichiometric and nonstoichiometric complexes. These PEC's are sterically stabilized by the PEO45 chains. By further increasing the PEO45 side-chain content (50 and 75%) of the cationic copolymer, small, water-soluble molecular complexes could be formed. The data suggest that PSS molecules and the charged backbone of the cationic brush form a compact core, and with sufficiently high PEO45 chain density (above 25%) molecular complexes are formed that are stable over prolonged times.
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PMID:Formation and stability of water-soluble, molecular polyelectrolyte complexes: effects of charge density, mixing ratio, and polyelectrolyte concentration. 1937 Oct 31


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