Polyelectrolyte surface

Morishima et al. [75, 76] have shown a remarkable effect of the polyelectrolyte surface potential on photoinduced ET in the laser photolysis of APh-x (8) and QPh-x (12) with viologens as electron acceptors. Decay profiles for the SPV (14) radical anion (SPV- ) generated by the photoinduced ET following a 347.1-nm laser excitation were monitored at 602 nm (Fig. 13) [75], For APh-9, the SPV- transient absorption persisted for several hundred microseconds after the laser pulse. The second-order rate constant (kb) for the back ET from SPV- to the oxidized Phen residue (Phen+) was estimated to be 8.7 x 107 M 1 s-1 for the APh-9-SPV system. For the monomer model system (AM(15)-SPV), on the other hand, kb was 2.8 x 109 M-1 s-1. This marked retardation of the back ET in the APh-9-SPV system is attributed to the electrostatic repulsion of SPV- by the electric field on the molecular surface of APh-9. The addition of NaCl decreases the electrostatic interaction. In fact, it increased the back ET rate. For example, at NaCl concentrations of 0.025 and 0.2 M, the value of kb increased to 2.5 x 108 and... 

Although the electrostatic field on the polyelectrolyte surface effectively impedes back ET, it is unable to retard very fast back ET or charge recombination of the primary ion pair within the photochemical cage. The overall quantum yield of photoinduced ET is actually controlled in most cases by the charge recombination. Hence, its retardation is the key problem for attaining high quantum yields in the photoinduced ET. 

Electric double layer forces between polyelectrolyte and non-polymer surfaces in aqueous media have also been studied very intensively [371,394,400-402]. The adhesion between polyelectrolyte surfaces could be reduced considerably by increasing the ionic strength of the medium [400]. Using an electrochemical cell and a gold coated tip, the adhesion between electroactive layer of p oly( vinyl-ferrocene) was controlled through the selective oxidation or reduction of the polymer films [401]. 

Moya S, Donath E, Sukhorukov GB et al (2000) Lipid coating on polyelectrolyte surface modified colloidal particles and polyelectrolyte capsules. Macromolecules 33 4538 1544... 

Borkovec, M., Jonsson, B., and Koper, G.J.M., Ionization processes and proton binding in polyprotic systems Small molecules, proteins, interfaces, and polyelectrolytes, Surface Colloid Sci., 16, 99, 2001. 

Zheng, H. P. Rubner, M. F. Hammond, P. T. Particle Assembly on Patterned Plus/Minus Polyelectrolyte Surfaces Via Polymer-on-Polymer Stamping. Langmuir 2002, 18, 4505—4510... 

The focus here is on the effects of dissolved natural organic matter (NOM) on the colloidal stability of particles in aquatic systems and, in particular, on the importance of the macromolecular nature of NOM in these effects. The approach used here has three components (1) modeling studies with mathematical polyelectrolytes, surfaces, and solvents (2) laboratory studies with well-characterized polyelectrolytes and particles and (3) laboratory studies with aquatic NOM, also using well-characterized particles. 

The second part is devoted to adsorption of polyelectrolytes at interfaces and to flocculation and stabilization of particles in adsorbing polymer solutions. A recent theory of the electrostatic adsorption barrier, some typical experimental results, and new approaches for studying the kinetics of polyelectrolyte adsorption are presented in the first chapter of this part. In the following chapters, results are collected on the electrical and hydrodynamic properties of colloid-polyelectrolyte surface layers, giving information on the structure of adsorbed layers and their influence on the interactions between colloidal particles examples and mechanisms are analyzed of polyelectrolyte-induced stabilization and fragmentation of colloidal aggregates ... 

Thomas J L, Barton S W, Tirrell D A (1994). Membrane solubilization by a hydro-phobic polyelectrolyte surface activity and membrane binding. Biophys. J. 67 1101-1106. 

Olenych SG, et al. Fibronectin and cell attachment to cell and protein resistant polyelectrolyte surfaces. Biomacromolecules 2005 6(6) 3252—8. 

In the limit of strong adsorption, the polyelectrolyte adsorption energy is large compared to the thermal fluctuations of the polymer chain. Hence, the structural properties of adsorbed chains are essentially governed by maximization of polyelectrolyte-surface electrostatic interactions and minimization of polyelectrolyte-polyelectrolyte repulsion [59]. Therefore, we consider a polyelectrolyte chain... 

We have shown that the scaling behavior of the critical adsorption parameters indeed changes dramatically in the limit of low salinity or large curvature of the surface, e.g., for the critical surface charge density from IcTcI for a plane to IcTcl Kof for a cylinder and to (xa) for the spherical surface. Maximal entropic penalty for polyelectrolyte confinement near a sphere and, concurrently, minimal energetic benefit from polyelectrolyte-surface attraction yield much larger... 

The issue of critical polyelectrolyte adsorption is intimately coupled to the polymer-mediated bridging attraction between oppositely charged macro-ions immersed in a polymer solution. Moreover, electrostatically driven self-assembly of single-stranded RNA molecules on the interior of positively charged capsids, as it occurs in many spherical and rod-Uke single-stranded viruses, offers another field for potential applications of our theoretical results. The WKB method developed above has recently been implemented to weak polyelectrolyte adsorption under confined conditions [49] and to adsorption onto low-dielectric interfaces [50]. The power of the WKB approach can even be extended to more complicated adsorption situations, such as patchy surfaces, specific charged patterns on concave and convex interfaces, Janus particles, etc., and other (nearly arbitrary) potentials of polyelectrolyte-surface interactions. This might open an avenue to approach more realistic situations of polyelectrolyte adsorption and to quantitatively reproduce experimental results in the future. 

The polyelectrolyte coated surface is uncharged, or in the case of AM-MAPTAC-30 weakly positively charged, before SDS is added. When SDS associates with an uncharged polyelectrolyte layer it will result in a recharging of the interface which results in the development of an electrostatic double layer and a less favorable polyelectrolyte-surface interaction. Thus, the polyelectrolyte-surfactant association at the mica surface is counteracted by electrostatic forces. Instead, it is driven by the hydrophobic interaction between the surfactant tails. This is confirmed by the cooperative nature of the association process observed for all polyelectrolyte-surfactant systems studied in this report. It is well known that hydrophobic interactions are very important also for the association between polyelectrolytes and surfactants in bulk solutions as demonstrated by the cooperativity of this process [16]. The... 

Consequently, many features of kinetics in micellar systems are related to reactions in monolayers and polyelectrolytes surfaces. 

A vast number of applications in different fields of Nanotechnology (interfacial phenomena, colloids, and nanomateiials) have been described for the materials obtained following this approach [81]. The formation and growth of polyelectrolyte multilayers is the result of an intricate balance of interactions [82], among their components polyelectrolyte—polyelectrolyte, polyelectrolyte—solvent, polyelectrolyte-surface, etc. The different interactions involved are governed by the complex interplay between electrostatic and entropic contributions, as well as solvent quality. 

Equation [23] represents the GC solution for point ions. A key development in the theory of electrolytes was the introduction of a finite distance of closest approach of ions to a charged surface by Stern and further elaborated upon by Grahame. The layer of ions directly adsorbed onto the surface constitutes the inner Helmholtz layer those ions that make contact but do not adsorb define the abovementioned distance of closest approach and constitute the outer Helmholtz or Stern layer. These modifications still admit an analytical solution to the GC equation Laplace s equation is solved in the Stern layer with the (linear) potential and (constant) field matched at the polyelectrolyte surface and to the outer GC solution. The adsorbed ions serve to reduce the charge density of the surface. Identification of the inner and outer Helmholtz layers has been particularly helpful in improving agreement between GC theory and electrochemical data. If we assign a common radius a to all electrolyte ions, then the identification of the interface atx = a actually... 

Each lattice point or finite element in the system must be assigned to represent either part of the polyelectrolyte or its ionic environment. To account for a finite distance of closest approach to the polyelectrolyte surface by ions of varying size, a rolling-sphere algorithm may be... 

Polarization of the electronic charge distribution around an ion including its hydration shell near a polyelectrolyte surface,... 

Kirkwood gave the first detailed derivation of the nonlinear PB equation, including corrections due to correlation (fluctuation) and finite ion size. These were elaborated on by Levine, culminating in a paper with Bell" ° dealing with the electric double layer near a polyelectrolyte surface. The leading terms in the Bell-Levine treatment were kept and some restrictions and approximations were applied to obtain a modified Poisson-Boltzmann (MPB) equation in the form of an integrodifference/differential equation that took into account the fluctuation potential of Kirkwood. 

Ghannoum, S., Xin, Y., Jaber, J. and Halaoui, LI. (2003) Self-assembly of polyacrylate-capped platinum nanopartides on a polyelectrolyte surface kinetics of adsorption and effect of ionic strength and deposition protocol. Langmuir, 19, 4804. 

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