The Experts below are selected from a list of 324 Experts worldwide ranked by ideXlab platform
Lars Wågberg - One of the best experts on this subject based on the ideXlab platform.
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Polyelectrolyte adsorption on thin cellulose films studied with reflectometry and quartz crystal microgravimetry with dissipation.
Biomacromolecules, 2009Co-Authors: Lars-erik Enarsson, Lars WågbergAbstract:Thin cellulose films were prepared by dissolving carboxymethylated cellulose fibers in N-methyl morpholine oxide and forming thin films on silicon wafers by spin-coating. The adsorption of cationic polyacrylamides and polydiallyldimethylammonium chloride onto these films was studied by stagnation point adsorption reflectometry (SPAR) and by quartz crystal microgravimetry with dissipation (QCM-D). The polyelectrolyte adsorption was studied by SPAR as a function of salt concentration, and it was found that the adsorption maximum was located at 1 mM NaCl for Polyelectrolytes of low charge density and at 10 mM NaCl for Polyelectrolytes of high charge density. Electrostatic screening led to complete elimination of the polyelectrolyte adsorption at salt concentrations of 300 mM NaCl. According to the QCM-D analysis, the cellulose films showed a pronounced swelling in water that took several hours to complete. Subsequent adsorption of Polyelectrolytes onto the cellulose films led to a release of water from the c...
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Polyelectrolyte adsorption on thin cellulose films studied with reflectometry and quartz crystal microgravimetry with dissipation.
Biomacromolecules, 2009Co-Authors: Lars-erik Enarsson, Lars WågbergAbstract:Thin cellulose films were prepared by dissolving carboxymethylated cellulose fibers in N-methyl morpholine oxide and forming thin films on silicon wafers by spin-coating. The adsorption of cationic polyacrylamides and polydiallyldimethylammonium chloride onto these films was studied by stagnation point adsorption reflectometry (SPAR) and by quartz crystal microgravimetry with dissipation (QCM-D). The polyelectrolyte adsorption was studied by SPAR as a function of salt concentration, and it was found that the adsorption maximum was located at 1 mM NaCl for Polyelectrolytes of low charge density and at 10 mM NaCl for Polyelectrolytes of high charge density. Electrostatic screening led to complete elimination of the polyelectrolyte adsorption at salt concentrations of 300 mM NaCl. According to the QCM-D analysis, the cellulose films showed a pronounced swelling in water that took several hours to complete. Subsequent adsorption of Polyelectrolytes onto the cellulose films led to a release of water from the cellulose, an effect that was substantial for Polyelectrolytes of high charge density at low salt concentrations. The total mass change including water could therefore show either an increase or a decrease during adsorption onto the cellulose films, depending on the experimental conditions.
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Diffusion of cationic Polyelectrolytes into cellulosic fibers.
Langmuir : the ACS journal of surfaces and colloids, 2008Co-Authors: Andrew T. Horvath, A. Elisabet Horvath, Tom Lindström, Lars WågbergAbstract:The penetration of cationic Polyelectrolytes into anionic cellulosic fibers was evaluated with fluorescent imaging techniques in order to clarify the mechanism and time scales for the diffusion process. The bulk charge of the cellulosic fibers indirectly creates a driving force for diffusion into the porous fiber wall, which is entropic in nature due to a release of counterions as the polyelectrolyte adsorbs. The individual bulk charges in the fiber cell wall also interact with the diffusing polyelectrolyte, such that the polyelectrolyte diffuses to the first available charge and consequently adsorbs and remains fixed. Thus, subsequent polyelectrolyte chains must first diffuse through the adsorbed polyelectrolyte layer before adsorbing to the next available bulk charges. This behavior differs from earlier suggested diffusion mechanisms, by which Polyelectrolytes were assumed to first adsorb to the outermost surface and then reptate into the pore structure. The time scales for polyelectrolyte diffusion were highly dependent on the flexibility of the chain, which was estimated from calculations of the persistence length. The persistence length ultimately depended on the charge density and electrolyte concentration. The charge density of the polyelectrolyte had a greater influence on the time scales for diffusion. High charge density Polyelectrolytes were observed to diffuse on a time scale of months, whereas the diffusion of low charge density Polyelectrolytes was measured on the order of hours. An influence of the chain length, that is, steric interactions due the persistence length of the polyelectrolyte and to the tortuosity of the porous structure of the fiber wall, could only be noted for low charge density Polyelectrolytes. Increasing the electrolyte concentration increased the chain flexibility by screening the electrostatic contribution to the persistence length, in turn inducing a faster diffusion process. However, a significant change in the diffusion behavior was observed at high electrolyte concentrations, at which the interaction between the polyelectrolyte charges and the fiber charges was almost completely screened.
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Adsorption of highly charged Polyelectrolytes onto an oppositely charged porous substrate.
Langmuir : the ACS journal of surfaces and colloids, 2008Co-Authors: Andrew T. Horvath, A. Elisabet Horvath, Tom Lindström, Lars WågbergAbstract:The adsorption behavior of highly charged cationic Polyelectrolytes onto porous substrates is electrostatic in nature and has been shown to be highly dependent on the polyelectrolyte properties. Co ...
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engineering of fibre surface properties by application of the polyelectrolyte multilayer concept part i modification of paper strength
Journal of Pulp and Paper Science (JPPS), 2002Co-Authors: Lars Wågberg, Sven Forsberg, A Johansson, P JunttiAbstract:Consecutive layers of cationic polyallylamine and anionic polyacrylic acid have been deposited on both unbeaten and beaten fully bleached cellulosic fibres. By preparing sheets of these fibres and by forming 5-10 layers of these Polyelectrolytes on the unbeaten fibres, it was possible to develop the same strength as can be achieved by conventional beating. Experiments show that considerable strength improvement can be achieved with this type of treatment also on beaten fibres. Atomic force microscopy investigations of multilayers of the polylectrolytes formed on silicon oxide surfaces showed that the thickness of 10 layers of Polyelectrolytes was 52 nm. Since the strength improvement was significant with 5 layers, it is suggested that a 26 nm thick multilayer of Polyelectrolytes is sufficient to create a strong joint between fibres. The structure of the polyelectrolyte multilayers formed on the fibres was not determined.
Lars-erik Enarsson - One of the best experts on this subject based on the ideXlab platform.
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Polyelectrolyte adsorption on thin cellulose films studied with reflectometry and quartz crystal microgravimetry with dissipation.
Biomacromolecules, 2009Co-Authors: Lars-erik Enarsson, Lars WågbergAbstract:Thin cellulose films were prepared by dissolving carboxymethylated cellulose fibers in N-methyl morpholine oxide and forming thin films on silicon wafers by spin-coating. The adsorption of cationic polyacrylamides and polydiallyldimethylammonium chloride onto these films was studied by stagnation point adsorption reflectometry (SPAR) and by quartz crystal microgravimetry with dissipation (QCM-D). The polyelectrolyte adsorption was studied by SPAR as a function of salt concentration, and it was found that the adsorption maximum was located at 1 mM NaCl for Polyelectrolytes of low charge density and at 10 mM NaCl for Polyelectrolytes of high charge density. Electrostatic screening led to complete elimination of the polyelectrolyte adsorption at salt concentrations of 300 mM NaCl. According to the QCM-D analysis, the cellulose films showed a pronounced swelling in water that took several hours to complete. Subsequent adsorption of Polyelectrolytes onto the cellulose films led to a release of water from the c...
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Polyelectrolyte adsorption on thin cellulose films studied with reflectometry and quartz crystal microgravimetry with dissipation.
Biomacromolecules, 2009Co-Authors: Lars-erik Enarsson, Lars WågbergAbstract:Thin cellulose films were prepared by dissolving carboxymethylated cellulose fibers in N-methyl morpholine oxide and forming thin films on silicon wafers by spin-coating. The adsorption of cationic polyacrylamides and polydiallyldimethylammonium chloride onto these films was studied by stagnation point adsorption reflectometry (SPAR) and by quartz crystal microgravimetry with dissipation (QCM-D). The polyelectrolyte adsorption was studied by SPAR as a function of salt concentration, and it was found that the adsorption maximum was located at 1 mM NaCl for Polyelectrolytes of low charge density and at 10 mM NaCl for Polyelectrolytes of high charge density. Electrostatic screening led to complete elimination of the polyelectrolyte adsorption at salt concentrations of 300 mM NaCl. According to the QCM-D analysis, the cellulose films showed a pronounced swelling in water that took several hours to complete. Subsequent adsorption of Polyelectrolytes onto the cellulose films led to a release of water from the cellulose, an effect that was substantial for Polyelectrolytes of high charge density at low salt concentrations. The total mass change including water could therefore show either an increase or a decrease during adsorption onto the cellulose films, depending on the experimental conditions.
Monica Olvera De La Cruz - One of the best experts on this subject based on the ideXlab platform.
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Dynamics of a driven confined polyelectrolyte solution
The Journal of chemical physics, 2020Co-Authors: Debarshee Bagchi, Monica Olvera De La CruzAbstract:The transport of Polyelectrolytes confined by oppositely charged surfaces and driven by a constant electric field is of interest in studies of DNA separation according to size. Using molecular dynamics simulations that include the surface polarization effect, we find that the mobilities of the Polyelectrolytes and their counterions change non-monotonically with the confinement surface charge density. For an optimum value of the confinement charge density, efficient separation of Polyelectrolytes can be achieved over a wide range of polyelectrolyte charge due to the differential friction imparted by oppositely charged confinement on the polyelectrolyte chains. Furthermore, by altering the placement of the charged confinement counterions, enhanced polyelectrolyte separation can be achieved by utilizing the surface polarization effect due to dielectric mismatch between the media inside and outside the confinement.
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Dynamics of a driven confined polyelectrolyte solution
arXiv: Soft Condensed Matter, 2020Co-Authors: Debarshee Bagchi, Monica Olvera De La CruzAbstract:The transport of Polyelectrolytes confined by oppositely charged surfaces and driven by a constant electric field is of interest in studies of DNA separation according to size. Using molecular dynamics simulations that include surface polarization effect, we find that the mobilities of the Polyelectrolytes and their counterions change non-monotonically with the confinement surface charge density. For an optimum value of the confinement charge density, efficient separation of Polyelectrolytes can be achieved over a wide range of polyelectrolyte charge due to the differential friction imparted by the oppositely charged confinement on the polyelectrolyte chains. Furthermore, by altering the placement of the charged confinement counterions, enhanced polyelectrolyte separation can be achieved by utilizing surface polarization effect due to dielectric mismatch between the media inside and outside the confinement.
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Adsorption of rod-like Polyelectrolytes onto weakly charged surfaces
The Journal of Chemical Physics, 2003Co-Authors: Hao Cheng, Monica Olvera De La CruzAbstract:We study the adsorption of strongly charged rod-like Polyelectrolytes onto weakly oppositely charged surfaces in salt solutions by equating the chemical potentials between the bulk and adsorbed Polyelectrolytes, and between the free and condensed ions along the rods. Lateral correlations between adsorbed Polyelectrolytes lead to nonoverlapping cells of radius R, which we study as a function of salt concentration (s), surface charge densities (σ), and polyelectrolyte charge density (1/b). We find a minimum in R and a maximum in the absolute value of the effective charge density of the surface-polyelectrolyte-ion system with increasing salt concentration. Charge inversion disappears in our model as the concentration of salt increases further. The critical salt concentration (sc) for polyelectrolyte adsorption scales as σα with α≈1.8. We find differences between weakly and strongly charged polyelectrolyte adsorption. While sc decreases as b increases in weakly charged Polyelectrolytes, it increases almost li...
Andrónico Neira-carrillo - One of the best experts on this subject based on the ideXlab platform.
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Amino Acid-Functionalized Polyelectrolyte Films as Bioactive Surfaces for Cell Adhesion
ACS Applied Materials & Interfaces, 2019Co-Authors: M. Leal, X. Briones, V. Villalobos, Y. Queneau, A. Leiva, H. Ríos, J. Pavez, C. Silva, C. Carrasco, Andrónico Neira-carrilloAbstract:Surfaces were prepared with polyelectrolyte derivatives of poly(styrene-alt-maleic anhydride) (PSMA) functionalized with amino acids of different hydropathy indices, with the aim of evaluating the effect of the chemical functionality of Polyelectrolytes on SH-SY5Y neuroblastoma cell adhesion. Functionalizing PSMA derivatives with L-glutamine, L-methionine, and L-tyrosine yielded PSMA-Gln, PSMA-Met, and PSMA-Tyr Polyelectrolytes, respectively. We first studied the adsorption behavior of PSMA functionalized with amino acids on silicon wafer surfaces modified with 3-aminopropyltriethoxysilane at pH 4.0 and 7.0 and at low and high ionic strengths. The highest rate of polyelectrolyte adsorption was at pH 4.0 and high ionic strength and was higher with the glutamine and tyrosine films. The advance contact angles (θ A) of the polyelectrolyte surfaces showed a moderate effect of ionic strength and pH on polyelectrolyte film wettability, with PSMA-Tyr being slightly more hydrophobic. Atomic force microscopy images of the polyelectrolyte surfaces showed two types of morphology: the well-defined globular nanostructure of PSMA-Met and PSMA-Tyr and densely packed nanofibrous-like structure of PSMA-Gln. The highest level of ionic strength caused a slight decrease in the size of the nanostructure that formed the surface domains, which was reflected in the degree of surface roughness. Cell adhesion assays with the polyelectrolyte film showed that SH-SY5Y neuroblastoma cells cultured on PSMA-Met present a well-extended morphology characterized by a stellate shape, with five or more actin-rich thin processes, whereas SH-SY5Y cells that were seeded on PSMA-Gln and PSMA-Tyr have a round morphology, with fewer and shorter processes. These results indicate that it is possible to modulate the surface characteristics of polyelectrolyte films based on their chemical functionality and environmental parameters such as pH and ionic strength in order to evaluate their effect on cell adhesion. Thus, surfaces prepared from Polyelectrolytes functionalized with amino acids are an attractive and simple platform for cell adhesion, which can be used in developing biomaterials with modulated surface properties.
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Amino Acid-Functionalized Polyelectrolyte Films as Bioactive Surfaces for Cell Adhesion
2019Co-Authors: M. S. Leal, X. Briones, V. Villalobos, Y. Queneau, A. Leiva, J. Pavez, C. Carrasco, H. E. Ríos, C. P. Silva, Andrónico Neira-carrilloAbstract:Surfaces were prepared with polyelectrolyte derivatives of poly(styrene-alt-maleic anhydride) (PSMA) functionalized with amino acids of different hydropathy indices, with the aim of evaluating the effect of the chemical functionality of Polyelectrolytes on SH-SY5Y neuroblastoma cell adhesion. Functionalizing PSMA derivatives with l-glutamine, l-methionine, and l-tyrosine yielded PSMA-Gln, PSMA-Met, and PSMA-Tyr Polyelectrolytes, respectively. We first studied the adsorption behavior of PSMA functionalized with amino acids on silicon wafer surfaces modified with 3-aminopropyltriethoxysilane at pH 4.0 and 7.0 and at low and high ionic strengths. The highest rate of polyelectrolyte adsorption was at pH 4.0 and high ionic strength and was higher with the glutamine and tyrosine films. The advance contact angles (θA) of the polyelectrolyte surfaces showed a moderate effect of ionic strength and pH on polyelectrolyte film wettability, with PSMA-Tyr being slightly more hydrophobic. Atomic force microscopy images of the polyelectrolyte surfaces showed two types of morphology: the well-defined globular nanostructure of PSMA-Met and PSMA-Tyr and densely packed nanofibrous-like structure of PSMA-Gln. The highest level of ionic strength caused a slight decrease in the size of the nanostructure that formed the surface domains, which was reflected in the degree of surface roughness. Cell adhesion assays with the polyelectrolyte film showed that SH-SY5Y neuroblastoma cells cultured on PSMA-Met present a well-extended morphology characterized by a stellate shape, with five or more actin-rich thin processes, whereas SH-SY5Y cells that were seeded on PSMA-Gln and PSMA-Tyr have a round morphology, with fewer and shorter processes. These results indicate that it is possible to modulate the surface characteristics of polyelectrolyte films based on their chemical functionality and environmental parameters such as pH and ionic strength in order to evaluate their effect on cell adhesion. Thus, surfaces prepared from Polyelectrolytes functionalized with amino acids are an attractive and simple platform for cell adhesion, which can be used in developing biomaterials with modulated surface properties
Bernd Tieke - One of the best experts on this subject based on the ideXlab platform.
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pervaporation separation of alcohol water mixtures using self assembled polyelectrolyte multilayer membranes of high charge density
Materials Science and Engineering: C, 2002Co-Authors: Ali Toutianoush, Bernd TiekeAbstract:The alcohol/water separation of polyelectrolyte multilayer membranes of high charge density prepared upon electrostatic layer-by-layer (LBL) adsorption of cationic and anionic Polyelectrolytes is described. Polyvinylamine (PVA) was used as the cationic polyelectrolyte, and polyvinylsulfonate (PVSu), polyvinylsulfate (PVS) and polyacrylate (PAA) were used as anionic Polyelectrolytes; the separation was studied under pervaporation conditions. At low water content in the feed (<20 wt.%), the strongly hydrophilic PVA/PVSu membrane is best suited for separation, while at higher water content the less hydrophilic PVA/PAA membrane exhibits the best separation. Membranes prepared at pH 1.7 with no salt present in the polyelectrolyte solution exhibit a substantially worse separation capability than membranes prepared at pH 1.7 in the presence of NaCl, or at pH 6.8 in the absence of salt. Use of PAA of low molecular weight (m.w. 5000) leads to membranes of much lower total flux than use of PAA of molecular weight 250,000.
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selective ion transport across self assembled alternating multilayers of cationic and anionic Polyelectrolytes
Langmuir, 2000Co-Authors: Lutz Krasemann And, Bernd TiekeAbstract:Ultrathin membranes consisting of an alternating sequence of cationic and anionic Polyelectrolytes were prepared by means of electrostatic layer-by-layer adsorption and investigated on their permeability for NaCl, Na2SO4, and MgCl2 in aqueous solution. It is demonstrated that the multi-bipolar structure of the polyelectrolyte membranes favors the separation of mono- and divalent ions by Donnan exclusion of the divalent ions. Various effects on the rate of ion permeation and the selectivity were investigated. Addition of salt to the polyelectrolyte solutions used for membrane preparation led to improved ion separation, while an increase of the pH had the opposite effect. Use of Polyelectrolytes with high charge density also improved the ion separation. Especially good results were obtained if membranes containing polyallylamine (PAH) as the cationic polyelectrolyte were used. For 60 layer pairs of PAH/polystyrenesulfonate, for example, a separation factor α for Na+/Mg2+ up to 112.5 and for Cl-/SO42- up to ...
