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Howard Allen Ketelson - One of the best experts on this subject based on the ideXlab platform.
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Shapes of Polyelectrolyte Titration Curves. 2. The Deviant Behavior of Labile Polyelectrolytes
Macromolecules, 2008Co-Authors: Yuguo Cui, Robert Pelton, Howard Allen KetelsonAbstract:Hydroxypropyl guar (HPG), a nonionic water soluble polymer, becomes an anionic Polyelectrolyte in the presence of borate or boronate ions which bind to HPG. However, the charge groups on the HPG−borate are labile which complicates the interpretation of Polyelectrolyte titration behavior. Specifically, Polyelectrolyte complex formation between HPG−borate and cationic poly(diallyldimethyl ammonium chloride), PDADMAC, stimulates further borate binding to HPG. We propose that labile Polyelectrolytes such as HPG−borate are new class of polylelectrolytes that fall outside conventional “strong” or “weak” Polyelectrolyte behavior.
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Shapes of Polyelectrolyte titration curves. 1. Well-behaved strong Polyelectrolytes.
Analytical chemistry, 2007Co-Authors: Robert Pelton, Bernard Cabane, Yuguo Cui, Howard Allen KetelsonAbstract:The charge content of aqueous polymers is measured routinely by Polyelectrolyte titrations in which an unknown polymer is titrated with an oppositely charged standard polymer solution, usually poly(diallyldimethyl ammonium chloride) or potassium poly(vinyl sulfate). Polyelectrolyte titration end points are frequently determined with a streaming current detector (SCD). The shapes of Polyelectrolyte titration curves from Polyelectrolytes with fixed electrical charges were simulated by a diffuse electrical double layer model. Well-behaved titration curves obtained with fixed charged Polyelectrolytes were fit by the modeling, giving support for the basic hypothesis that the net charge of material adsorbed on the SCD wall is a linear function of the volume of added titrant. The shapes of titration curves from deviant systems such as poly(vinyl alcohol)−borate cannot be predicted by the model.
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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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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Conformation of preadsorbed Polyelectrolyte layers on silica studied by secondary adsorption of colloidal silica
Journal of Colloid and Interface Science, 2008Co-Authors: Lars-erik Enarsson, Lars WågbergAbstract:The conformation of cationic Polyelectrolytes preadsorbed on macroscopic silica surfaces was studied before and after addition of colloidal silica (CS) and compared to the fixation capacity of CS. The study included two Polyelectrolytes of equal charge density, cationic polyacrylamide and cationic dextran. Adsorbed amounts were determined with stagnation point adsorption reflectometry (SPAR) and quartz crystal microgravimetry (QCM). Unsaturated layers of Polyelectrolyte were formed in SPAR by stopping the adsorption at a fractional coverage relative to saturation adsorption. These layers were probed by secondary saturation adsorption of colloidal silica (CS). At low salt concentrations a high fractional coverage of Polyelectrolyte was required to attain adsorption of CS, while significant adsorption of CS was found also for low fractional coverages of Polyelectrolyte at salt concentrations above 10 mM NaCl. Saturation adsorption of cationic polyacrylamide (CPAM) and cationic dextran (Cdextran) onto the silica surface was found to be similar, while the secondary adsorption of CS was significantly higher onto preadsorbed CPAM compared with Cdextran. The QCM and SPAR data together indicated that the adsorbed layer of Cdextran was thinner than CPAM, and that a loose, expanded layer was formed after adsorption of CS on CPAM but not on Cdextran.
Akira Baba - One of the best experts on this subject based on the ideXlab platform.
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Polyelectrolyte adsorption processes characterized in situ using the quartz crystal microbalance technique alternate adsorption properties in ultrathin polymer films
Colloids and Surfaces A: Physicochemical and Engineering Aspects, 2000Co-Authors: Akira Baba, Futao Kaneko, Rigoberto C AdvinculaAbstract:Abstract The alternate adsorption processes of Polyelectrolytes from solution have been investigated in situ using a functionalized (gold electrode) quartz substrate via the quartz crystal microbalance (QCM) technique. The deposition process involved the alternate layer by layer electrostatic (Coulombic) interaction between oppositely charged adsorbing Polyelectrolytes resulting in ultrathin multilayer films. Three kinds of Polyelectrolyte combinations were used: poly(diallyldimethylammonium chloride) (PDADMAC), poly(ethylenimine) (PEI) and poly(allylamine hydrochloride) (PAH) as the cationic polymers and poly(sodium-4-styrensulfonate) (PSS) as the anionic polymer for polycation/polyanion combinations. The electrical behavior of the piezoelectric ‘quartz crystal’ was sensitive to the adsorption properties of the Polyelectrolytes, thus allowing close observation of the time-dependent adsorption processes. The adsorption relationship was explored for different Polyelectrolyte pair-combinations, alternate solution concentration and the presence of rinsing and drying steps. The results showed that the amount of frequency change is mostly dependent on the immediate subphase environment of the crystal surface, i.e. aqueous environment versus air in relation to the classic Sauerbrey equation.
Robert Pelton - One of the best experts on this subject based on the ideXlab platform.
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Shapes of Polyelectrolyte Titration Curves. 2. The Deviant Behavior of Labile Polyelectrolytes
Macromolecules, 2008Co-Authors: Yuguo Cui, Robert Pelton, Howard Allen KetelsonAbstract:Hydroxypropyl guar (HPG), a nonionic water soluble polymer, becomes an anionic Polyelectrolyte in the presence of borate or boronate ions which bind to HPG. However, the charge groups on the HPG−borate are labile which complicates the interpretation of Polyelectrolyte titration behavior. Specifically, Polyelectrolyte complex formation between HPG−borate and cationic poly(diallyldimethyl ammonium chloride), PDADMAC, stimulates further borate binding to HPG. We propose that labile Polyelectrolytes such as HPG−borate are new class of polylelectrolytes that fall outside conventional “strong” or “weak” Polyelectrolyte behavior.
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Shapes of Polyelectrolyte titration curves. 1. Well-behaved strong Polyelectrolytes.
Analytical chemistry, 2007Co-Authors: Robert Pelton, Bernard Cabane, Yuguo Cui, Howard Allen KetelsonAbstract:The charge content of aqueous polymers is measured routinely by Polyelectrolyte titrations in which an unknown polymer is titrated with an oppositely charged standard polymer solution, usually poly(diallyldimethyl ammonium chloride) or potassium poly(vinyl sulfate). Polyelectrolyte titration end points are frequently determined with a streaming current detector (SCD). The shapes of Polyelectrolyte titration curves from Polyelectrolytes with fixed electrical charges were simulated by a diffuse electrical double layer model. Well-behaved titration curves obtained with fixed charged Polyelectrolytes were fit by the modeling, giving support for the basic hypothesis that the net charge of material adsorbed on the SCD wall is a linear function of the volume of added titrant. The shapes of titration curves from deviant systems such as poly(vinyl alcohol)−borate cannot be predicted by the model.
Vincent Ball - One of the best experts on this subject based on the ideXlab platform.
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Shear induced changes in the streaming potential of Polyelectrolyte multilayer films
Colloids and Surfaces A: Physicochemical and Engineering Aspects, 2015Co-Authors: Christian Ringwald, Vincent BallAbstract:Abstract Streaming potential measurement is one of the most frequently used characterization methods of Polyelectrolyte multilayer films. In most cases, the adsorption of a Polyelectrolyte occurs up to an overcompensation of the surface charge. Herein, we generalize previous findings that the obtained streaming potential (transformed into a relative ζ potential) is dependent on the history of the measurement and in particular that shear stresses due to the flow of the solution induce a reduction in the absolute values of the ζ potential. These findings show that huge care should be taken when defining an experimental protocol aimed to measure the zeta potential of Polyelectrolyte multilayer films using the streaming potential method. Ideally, to avoid the influence of shear induced desorption of Polyelectrolytes on the zeta potential values, Polyelectrolyte multilayer films made from different number of layers should be characterized independently under overall identical conditions.