The Experts below are selected from a list of 321 Experts worldwide ranked by ideXlab platform

Lars Wågberg - One of the best experts on this subject based on the ideXlab platform.

  • Thermo-responsive nanofibrillated cellulose by Polyelectrolyte Adsorption
    European Polymer Journal, 2013
    Co-Authors: Emma Larsson, Lars Wågberg, Carmen Cobo Sanchez, Christian Porsch, Erdem Karabulut, Anna Carlmark
    Abstract:

    In this study, thermo-responsive nanofibrillated cellulose (NFC) has been produced by the Adsorption of thermo-responsive Polyelectrolytes to the NFC. Three block copolymers were synthesized in whi ...

  • Polyelectrolyte Adsorption on thin cellulose films studied with reflectometry and quartz crystal microgravimetry with dissipation.
    Biomacromolecules, 2009
    Co-Authors: Lars-erik Enarsson, Lars Wågberg
    Abstract:

    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...

  • Polyelectrolyte Adsorption on thin cellulose films studied with reflectometry and quartz crystal microgravimetry with dissipation.
    Biomacromolecules, 2009
    Co-Authors: Lars-erik Enarsson, Lars Wågberg
    Abstract:

    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.

  • Adsorption kinetics of cationic Polyelectrolytes studied with stagnation point Adsorption reflectometry and quartz crystal microgravimetry.
    Langmuir : the ACS journal of surfaces and colloids, 2008
    Co-Authors: Lars-erik Enarsson, Lars Wågberg
    Abstract:

    The effects of charge density, pH, and salt concentration on Polyelectrolyte Adsorption onto the oxidized surface of silicon wafers were studied using stagnation point Adsorption reflectometry and ...

  • Kinetics of Polyelectrolyte Adsorption on cellulosic fibers
    Langmuir, 2001
    Co-Authors: Lars Wågberg, Rickard Hägglund
    Abstract:

    The present investigation has been focused on studying the Adsorption of three different molecular mass fractions of a polydimethyldiallylammonium chloride (DMDAAC) (8750 (LMw), 48 000 (MMw), and 1 200 000 (HMw)) on bleached chemical fibers. Both kinetics of Adsorption and equilibrium Adsorption measurements have been conducted, and the Adsorption has been measured by Polyelectrolyte titration. The results show that the LMw polymer can reach all the charges in the fiber wall whereas the MMw and HMw can only reach the charges on the external surfaces of the fibers. It is also shown that the kinetics of Adsorption of the LMw polymer is not at all affected by the presence of a saturated layer of HMw polymer on the surface of the fibers. Finally the results from the investigation show that it is possible to have a full coverage of the external surface of the fibers by a high molecular mass polymer and a full coverage of the internal surface of the fibers with a low molecular mass polymer provided that the high molecular mass polymer is adsorbed before addition of the low molecular mass polymer. This is true if the polymers are adsorbed to the same type of groups on the fibers. A simplistic model for describing ployelectrolyte Adsorption in turbulent flow also shows good agreement with measured values for the low molecular mass Polyelectrolyte whereas the agreement for the high molecular Polyelectrolyte is not as good. For the high molecular mass Polyelectrolyte a more sophisticated model is needed.

Lars-erik Enarsson - One of the best experts on this subject based on the ideXlab platform.

Satish Kumar - One of the best experts on this subject based on the ideXlab platform.

  • Dynamic Multiscale Simulation of Polyelectrolyte Nanoassemblies
    2008
    Co-Authors: Satish Kumar
    Abstract:

    Abstract : The goal of this project is to develop a fundamental understanding of how fluid flows, electric fields, and surface patterning affect Polyelectrolyte Adsorption, self-assembly, and transport near solid surfaces. Polyelectrolytes are charged polymers whose behavior is central to Army-relevant technologies (e.g., biochemical sensors, surface functionalization) but poorly understood. Brownian dynamics simulations---a coarse-grained simulation method suitable for describing non-equilibrium polymer behavior---have been applied to study Polyelectrolyte Adsorption in shear flow, Polyelectrolyte Adsorption onto patterned surfaces, dendrimer and hyperbranched polymer Adsorption, and Polyelectrolyte electrophoresis. Along with complementary continuum-level models, the simulations yield insight into how to design fluid flows, electric fields, and surface patterning to control the behavior of single Polyelectrolyte molecules. The knowledge gained lays the foundation for future studies involving multiple molecules and more complex physical phenomena.

  • Brownian dynamics simulations of Polyelectrolyte Adsorption in shear flow: effects of solvent quality and charge patterning.
    The Journal of chemical physics, 2008
    Co-Authors: Nazish Hoda, Satish Kumar
    Abstract:

    We probe the effects of solvent quality and charge patterning on Polyelectrolyte Adsorption in shear flow using Brownian dynamics simulations with hydrodynamic interaction (HI). The Polyelectrolyte is modeled as a freely jointed bead-rod chain, and electrostatic and non-electrostatic interactions are accounted for by using screened Coulombic and Lennard-Jones potentials, respectively. In the absence of flow, the conformation of a Polyelectrolyte molecule adsorbed onto a uniformly charged surface changes from flat to globular with an increase in bead-bead attraction (hydrophobicity), consistent with prior experimental observations. In the presence of flow, migration due to bead-wall HI and, as a consequence, desorption decrease with an increase in bead-bead attraction, implying that flow-induced desorption is more difficult under poor-solvent conditions. When bead-bead non-electrostatic attraction is strong, desorption can be enhanced by increasing bead-bead electrostatic repulsion. Analogous to the effect...

  • Kinetic theory of Polyelectrolyte Adsorption in shear flow
    Journal of Rheology, 2007
    Co-Authors: Nazish Hoda, Satish Kumar
    Abstract:

    The effect of hydrodynamic interactions on the Adsorption of a Polyelectrolyte molecule onto a wall in shear flow is investigated using a bead-spring dumbbell model. Bead-bead and bead-wall electrostatic interactions are taken into account using screened Coulombic interactions, and the hydrodynamic interactions are incorporated using the approach proposed by Ma and Graham [Phys. Fluids 17, 083103 (2005)]. An analytical expression for the concentration profile of the Polyelectrolyte is derived which predicts a competition between bead-wall hydrodynamic interactions and bead-wall electrostatic attraction. The behavior of the concentration profile is explored as a function of the Weissenberg number, surface (wall) charge density, charge on the beads, and screening length. The charge on the beads assists migration of the dumbbell away from an uncharged wall, whereas for an oppositely charged wall it increases the probability of finding the dumbbell close to the wall. In some cases, the concentration profile s...

  • Brownian dynamics simulations of Polyelectrolyte Adsorption in shear flow
    The Journal of chemical physics, 2005
    Co-Authors: Ajay S. Panwar, Satish Kumar
    Abstract:

    Brownian dynamics simulations are used to study the Adsorption of an isolated Polyelectrolyte molecule onto an oppositely charged flat surface in the absence and the presence of an imposed shear flow. The Polyelectrolyte is modeled as a freely jointed bead-rod chain where excluded volume interactions are incorporated by using a hard-sphere potential. The total charge along the backbone is distributed uniformly among all the beads, and the beads are allowed to interact with one another and the charged surface through screened Coulombic interactions. The simulations are performed by placing the molecule a fixed distance above the surface, and the Adsorption behavior is then studied as a function of screening length. In the absence of an imposed flow, the chain is found to lie flat and extended on the adsorbing surface in the limit of weak screening, whereas in the limit of strong screening it desorbs from the surface and attains free-solution behavior. For intermediate screening, only a small portion of the chain adsorbs and it becomes highly extended in the direction normal to the surface. An imposed shear flow tends to orient the chain in the direction of flow and also leads to increased contact of the chain with the surface.

Serge Stoll - One of the best experts on this subject based on the ideXlab platform.

  • Polyelectrolyte Adsorption on an Oppositely Charged Spherical Particle. Chain Rigidity Effects
    Macromolecules, 2002
    Co-Authors: Serge Stoll, Pierre Chodanowski
    Abstract:

    We used Monte Carlo simulations to study the formation of complexes between a flexible, semiflexible, and rigid Polyelectrolyte and an oppositely charged spherical particle. Polyelectrolyte Adsorption on a small particle, whose surface curvature effect is expected to limit the amount of adsorbed monomers, was considered. We focused on the effects of the intrinsic Polyelectrolyte rigidity and ionic concentration of the solution and investigated the Adsorption/desorption limit and conformation of the adsorbed Polyelectrolyte. Polyelectrolyte Adsorption is controlled by several competing effects such as the electrostatic confinement energy of the chain due to the electrostatic repulsions between the charged monomers, Polyelectrolyte intrinsic flexibility, and electrostatic attractive interaction between the Polyelectrolyte monomers and the particle. On one hand, rigidity and electrostatic repulsions force the Polyelectrolyte to adopt extended conformations and limit the number of monomers that may be attache...

  • Polyelectrolyte Adsorption on charged particles: Ionic concentration and particle size effects—A Monte Carlo approach
    The Journal of Chemical Physics, 2001
    Co-Authors: Pierre Chodanowski, Serge Stoll
    Abstract:

    The complexation between a charged polymer and an oppositely charged spherical particle is investigated using Monte Carlo simulations. Electrostatic interactions are described in the Debye–Huckel approximation. The influence of particle size and ionic concentration on the Adsorption/desorption limit, interfacial structure of the adsorbed layer, amount of adsorbed polymer, and the overcharging issue is investigated. Attention is focused on Polyelectrolyte Adsorption on small spherical particles whose surface curvature effects are expected to limit the amount of adsorbed monomers, large particles that allow the Polyelectrolyte to spread to the same extent as on a flat surface, and particles whose radius is close to the Polyelectrolyte radius of gyration so that the chain can completely wrap around it. The formation of a Polyelectrolyte/particle complex and the conformations of the adsorbed Polyelectrolyte are found to result from two competing effects: the electrostatic repulsions between the chain monomers...

  • Polyelectrolyte Adsorption on charged particles: Ionic concentration and particle size effects—A Monte Carlo approach
    The Journal of Chemical Physics, 2001
    Co-Authors: Pierre Chodanowski, Serge Stoll
    Abstract:

    The complexation between a charged polymer and an oppositely charged spherical particle is investigated using Monte Carlo simulations. Electrostatic interactions are described in the Debye–Huckel approximation. The influence of particle size and ionic concentration on the Adsorption/desorption limit, interfacial structure of the adsorbed layer, amount of adsorbed polymer, and the overcharging issue is investigated. Attention is focused on Polyelectrolyte Adsorption on small spherical particles whose surface curvature effects are expected to limit the amount of adsorbed monomers, large particles that allow the Polyelectrolyte to spread to the same extent as on a flat surface, and particles whose radius is close to the Polyelectrolyte radius of gyration so that the chain can completely wrap around it. The formation of a Polyelectrolyte/particle complex and the conformations of the adsorbed Polyelectrolyte are found to result from two competing effects: the electrostatic repulsions between the chain monomers which force the Polyelectrolyte to adopt extended conformations and limit the number of monomers which may be attached in particular to small particles, and the electrostatic attractive interactions between the particle and the monomers forcing the charged polymer to undergo structural transition and collapse at the particle surface. It is shown that Adsorption is favored by increasing particle size and decreasing ionic concentration. Trains are favored at low ionic concentrations while loops (prior desorption) are favored more when increasing the ionic strength. Below a critical particle size, by decreasing the ionic strength, electrostatic repulsions between the adsorbed monomers force the Polyelectrolyte to form protuding tails in solution, hence decreasing the amount of Polyelectrolyte Adsorption. By decreasing the particle size still further, the low ionic concentration regime is dominated by monomer–monomer repulsions; the polymer partially wraps around or becomes tangential to the particle and two tails extend in opposite directions. The complex may or may not exhibit charge inversion depending on the particle size and ionic concentration. We find that charge reversal increases with salt concentration and reaches a maximum when the Polyelectrolyte is able to wrap around the particle completely.

  • Polyelectrolyte Adsorption on charged particles ionic concentration and particle size effects a monte carlo approach
    Journal of Chemical Physics, 2001
    Co-Authors: Pierre Chodanowski, Serge Stoll
    Abstract:

    The complexation between a charged polymer and an oppositely charged spherical particle is investigated using Monte Carlo simulations. Electrostatic interactions are described in the Debye–Huckel approximation. The influence of particle size and ionic concentration on the Adsorption/desorption limit, interfacial structure of the adsorbed layer, amount of adsorbed polymer, and the overcharging issue is investigated. Attention is focused on Polyelectrolyte Adsorption on small spherical particles whose surface curvature effects are expected to limit the amount of adsorbed monomers, large particles that allow the Polyelectrolyte to spread to the same extent as on a flat surface, and particles whose radius is close to the Polyelectrolyte radius of gyration so that the chain can completely wrap around it. The formation of a Polyelectrolyte/particle complex and the conformations of the adsorbed Polyelectrolyte are found to result from two competing effects: the electrostatic repulsions between the chain monomers...

  • Polyelectrolyte Adsorption on charged particles ionic concentration and particle size effects a monte carlo approach
    Journal of Chemical Physics, 2001
    Co-Authors: Pierre Chodanowski, Serge Stoll
    Abstract:

    The complexation between a charged polymer and an oppositely charged spherical particle is investigated using Monte Carlo simulations. Electrostatic interactions are described in the Debye–Huckel approximation. The influence of particle size and ionic concentration on the Adsorption/desorption limit, interfacial structure of the adsorbed layer, amount of adsorbed polymer, and the overcharging issue is investigated. Attention is focused on Polyelectrolyte Adsorption on small spherical particles whose surface curvature effects are expected to limit the amount of adsorbed monomers, large particles that allow the Polyelectrolyte to spread to the same extent as on a flat surface, and particles whose radius is close to the Polyelectrolyte radius of gyration so that the chain can completely wrap around it. The formation of a Polyelectrolyte/particle complex and the conformations of the adsorbed Polyelectrolyte are found to result from two competing effects: the electrostatic repulsions between the chain monomers which force the Polyelectrolyte to adopt extended conformations and limit the number of monomers which may be attached in particular to small particles, and the electrostatic attractive interactions between the particle and the monomers forcing the charged polymer to undergo structural transition and collapse at the particle surface. It is shown that Adsorption is favored by increasing particle size and decreasing ionic concentration. Trains are favored at low ionic concentrations while loops (prior desorption) are favored more when increasing the ionic strength. Below a critical particle size, by decreasing the ionic strength, electrostatic repulsions between the adsorbed monomers force the Polyelectrolyte to form protuding tails in solution, hence decreasing the amount of Polyelectrolyte Adsorption. By decreasing the particle size still further, the low ionic concentration regime is dominated by monomer–monomer repulsions; the polymer partially wraps around or becomes tangential to the particle and two tails extend in opposite directions. The complex may or may not exhibit charge inversion depending on the particle size and ionic concentration. We find that charge reversal increases with salt concentration and reaches a maximum when the Polyelectrolyte is able to wrap around the particle completely.

Pierre Chodanowski - One of the best experts on this subject based on the ideXlab platform.

  • Polyelectrolyte Adsorption on an Oppositely Charged Spherical Particle. Chain Rigidity Effects
    Macromolecules, 2002
    Co-Authors: Serge Stoll, Pierre Chodanowski
    Abstract:

    We used Monte Carlo simulations to study the formation of complexes between a flexible, semiflexible, and rigid Polyelectrolyte and an oppositely charged spherical particle. Polyelectrolyte Adsorption on a small particle, whose surface curvature effect is expected to limit the amount of adsorbed monomers, was considered. We focused on the effects of the intrinsic Polyelectrolyte rigidity and ionic concentration of the solution and investigated the Adsorption/desorption limit and conformation of the adsorbed Polyelectrolyte. Polyelectrolyte Adsorption is controlled by several competing effects such as the electrostatic confinement energy of the chain due to the electrostatic repulsions between the charged monomers, Polyelectrolyte intrinsic flexibility, and electrostatic attractive interaction between the Polyelectrolyte monomers and the particle. On one hand, rigidity and electrostatic repulsions force the Polyelectrolyte to adopt extended conformations and limit the number of monomers that may be attache...

  • Polyelectrolyte Adsorption on charged particles: Ionic concentration and particle size effects—A Monte Carlo approach
    The Journal of Chemical Physics, 2001
    Co-Authors: Pierre Chodanowski, Serge Stoll
    Abstract:

    The complexation between a charged polymer and an oppositely charged spherical particle is investigated using Monte Carlo simulations. Electrostatic interactions are described in the Debye–Huckel approximation. The influence of particle size and ionic concentration on the Adsorption/desorption limit, interfacial structure of the adsorbed layer, amount of adsorbed polymer, and the overcharging issue is investigated. Attention is focused on Polyelectrolyte Adsorption on small spherical particles whose surface curvature effects are expected to limit the amount of adsorbed monomers, large particles that allow the Polyelectrolyte to spread to the same extent as on a flat surface, and particles whose radius is close to the Polyelectrolyte radius of gyration so that the chain can completely wrap around it. The formation of a Polyelectrolyte/particle complex and the conformations of the adsorbed Polyelectrolyte are found to result from two competing effects: the electrostatic repulsions between the chain monomers...

  • Polyelectrolyte Adsorption on charged particles: Ionic concentration and particle size effects—A Monte Carlo approach
    The Journal of Chemical Physics, 2001
    Co-Authors: Pierre Chodanowski, Serge Stoll
    Abstract:

    The complexation between a charged polymer and an oppositely charged spherical particle is investigated using Monte Carlo simulations. Electrostatic interactions are described in the Debye–Huckel approximation. The influence of particle size and ionic concentration on the Adsorption/desorption limit, interfacial structure of the adsorbed layer, amount of adsorbed polymer, and the overcharging issue is investigated. Attention is focused on Polyelectrolyte Adsorption on small spherical particles whose surface curvature effects are expected to limit the amount of adsorbed monomers, large particles that allow the Polyelectrolyte to spread to the same extent as on a flat surface, and particles whose radius is close to the Polyelectrolyte radius of gyration so that the chain can completely wrap around it. The formation of a Polyelectrolyte/particle complex and the conformations of the adsorbed Polyelectrolyte are found to result from two competing effects: the electrostatic repulsions between the chain monomers which force the Polyelectrolyte to adopt extended conformations and limit the number of monomers which may be attached in particular to small particles, and the electrostatic attractive interactions between the particle and the monomers forcing the charged polymer to undergo structural transition and collapse at the particle surface. It is shown that Adsorption is favored by increasing particle size and decreasing ionic concentration. Trains are favored at low ionic concentrations while loops (prior desorption) are favored more when increasing the ionic strength. Below a critical particle size, by decreasing the ionic strength, electrostatic repulsions between the adsorbed monomers force the Polyelectrolyte to form protuding tails in solution, hence decreasing the amount of Polyelectrolyte Adsorption. By decreasing the particle size still further, the low ionic concentration regime is dominated by monomer–monomer repulsions; the polymer partially wraps around or becomes tangential to the particle and two tails extend in opposite directions. The complex may or may not exhibit charge inversion depending on the particle size and ionic concentration. We find that charge reversal increases with salt concentration and reaches a maximum when the Polyelectrolyte is able to wrap around the particle completely.

  • Polyelectrolyte Adsorption on charged particles ionic concentration and particle size effects a monte carlo approach
    Journal of Chemical Physics, 2001
    Co-Authors: Pierre Chodanowski, Serge Stoll
    Abstract:

    The complexation between a charged polymer and an oppositely charged spherical particle is investigated using Monte Carlo simulations. Electrostatic interactions are described in the Debye–Huckel approximation. The influence of particle size and ionic concentration on the Adsorption/desorption limit, interfacial structure of the adsorbed layer, amount of adsorbed polymer, and the overcharging issue is investigated. Attention is focused on Polyelectrolyte Adsorption on small spherical particles whose surface curvature effects are expected to limit the amount of adsorbed monomers, large particles that allow the Polyelectrolyte to spread to the same extent as on a flat surface, and particles whose radius is close to the Polyelectrolyte radius of gyration so that the chain can completely wrap around it. The formation of a Polyelectrolyte/particle complex and the conformations of the adsorbed Polyelectrolyte are found to result from two competing effects: the electrostatic repulsions between the chain monomers...

  • Polyelectrolyte Adsorption on charged particles ionic concentration and particle size effects a monte carlo approach
    Journal of Chemical Physics, 2001
    Co-Authors: Pierre Chodanowski, Serge Stoll
    Abstract:

    The complexation between a charged polymer and an oppositely charged spherical particle is investigated using Monte Carlo simulations. Electrostatic interactions are described in the Debye–Huckel approximation. The influence of particle size and ionic concentration on the Adsorption/desorption limit, interfacial structure of the adsorbed layer, amount of adsorbed polymer, and the overcharging issue is investigated. Attention is focused on Polyelectrolyte Adsorption on small spherical particles whose surface curvature effects are expected to limit the amount of adsorbed monomers, large particles that allow the Polyelectrolyte to spread to the same extent as on a flat surface, and particles whose radius is close to the Polyelectrolyte radius of gyration so that the chain can completely wrap around it. The formation of a Polyelectrolyte/particle complex and the conformations of the adsorbed Polyelectrolyte are found to result from two competing effects: the electrostatic repulsions between the chain monomers which force the Polyelectrolyte to adopt extended conformations and limit the number of monomers which may be attached in particular to small particles, and the electrostatic attractive interactions between the particle and the monomers forcing the charged polymer to undergo structural transition and collapse at the particle surface. It is shown that Adsorption is favored by increasing particle size and decreasing ionic concentration. Trains are favored at low ionic concentrations while loops (prior desorption) are favored more when increasing the ionic strength. Below a critical particle size, by decreasing the ionic strength, electrostatic repulsions between the adsorbed monomers force the Polyelectrolyte to form protuding tails in solution, hence decreasing the amount of Polyelectrolyte Adsorption. By decreasing the particle size still further, the low ionic concentration regime is dominated by monomer–monomer repulsions; the polymer partially wraps around or becomes tangential to the particle and two tails extend in opposite directions. The complex may or may not exhibit charge inversion depending on the particle size and ionic concentration. We find that charge reversal increases with salt concentration and reaches a maximum when the Polyelectrolyte is able to wrap around the particle completely.