Polyelectrolytes adsorption from solution

Electrode surfaces can be modified by redox polyelectrolytes via a sol-gel process, yielding random redox hydrogels or by layer-by-layer self-assembly of different redox and nonredox polyelectrolytes by alternate electrostatic adsorption from solutions containing the polyelectrolytes to produce highly organized redox-active ultrathin multilayers. 

The polyelectrolyte multilayers employed in these studies consisted of alternating layers of poly(ethyleneimine) (PEI) and poly(4-styrenesulfonicacid) sodium salt (PSS) and were prepared via adsorption from solution as described by Decher et al. [26] on functionalized Au- or SiOx substrates. The lipids used for the preparation of the bilayers were dimyristoyl-L-a-phosphatidylglycerol (DMPG, negatively charged in aqueous solution) and DMPC. Uni-lamellar lipid vesicles were prepared via the extrusion technique. 

Hesselink FTh. Adsorption of polyelectrolytes from dilute solution. In Parfitt CD, Rochester CH, eds. Adsorption from Solution at the Solid—Liquid Interface. London Academic Press, 1983 277-412. 

As presented in the introduction, the nature of the substrate used for the above-described electrostatic layer-by-layer deposition is not cmcial, as long as it is charged. For example, PAH/PSS multilayers have been prepared on plasma-treated glass [85,86], as cleaved mica [87], silicon functionalized by 3-aminopro-pyldimethoxysilane [88], surface-oxidized poly(4-methyl-l-pentene) [89], chemically modified poly(chlorotrifluoroethylene) (PCTFE) [90,91], plasma-modified poly(tetrafiuoroethylene) (FIFE) [92,93], chemically modified as well as untreated poly(ethylene terephtalate) (PET) [94], gold surfaces modified with mer-captopropionic acid [76], and many others. PAH/PSS multilayers have also been grown on chemically modified polystyrene [95] and melamine formaldehyde latex particles [96,97]. Multilayer assembly on latex particles was either accomplished by adsorption from solutions of high polyelectrolyte concentration with... 

In adsorption studies from saline environments it is necessary to prepare the water-soluble polymer and peptized montmorillonite in fresh water at high concentrations and to add each to a saline solution. Polyelectrolytes will frequently not "yield" the same viscosity as when they are dissolved in fresh water. Montmorillonite will flocculate in saline solutions. With fresh water mixing of components, reproducible results are obtained in the saline studies. After component mixing, agitation of the slurry is maintained with gentle stirring via... 

A large number of examples of redox polyelectrolyte monolayers have been reported [42[. Anson described the adsorption of poly(acrylic acid) onto glassy carbon with electrostatic binding of Ru(NH3)6 and Co(NH3)6 ions from solution [43]. Finklea [44] adsorbed poly(4-vinyl-I-methyl-pyridinium methylsulfate) on self-assembled mercapto-undecanoic self-assembled monolayer (SAM) on gold electrodes to... 

In any consideration of what is presently known regarding adsorption from aqueous solution it is necessary to distinguish between neutral species, simple ions, complex ions, surface active agents, polyelectrolytes, and charged and uncharged high polymers. Much of the data available in the literature relates to the adsorption of polymers and complex-... 

In aqueous solutions the carboxylate groups of the grafted mercapto components can act as anchors for PVFA-co-PVAm molecules. The adsorption from differently concentrated PVFA-co-PVAm solutions (0.3 pmol L-1 to 3000 pmol L-1) gave polyelectrolyte layer thicknesses between 0.9 and 2.7 nm (determined by ellipsometry and angle-resolved XPS). The values found are in good agreement with the layer thicknesses on bare silicon wafer surfaces [97]. The layer thicknesses of the pre-adsorbed mercapto compounds range from 0.5 to 0.9 nm. That means that at very low polyelectroyte concentrations in the stock solution no increase in layer thickness was ob-... 

This chapter shows that a unified explanation can be given of the adsorption from dilute aqueous solutions of different organic solutes, from nonelectrolytes to electrolytes, polyelectrolytes, and bacteria. Thus, the adsorption process is a complex interplay between electrostatic and nonelectrostatic interactions. Electrostatic interactions depend on the solution pH and ionic strength. The former controls the charge on the carbon surface and on the adsorptive... 

Evers OA, Fleer GJ, Scheutjens JMHM, Lyklema J. Adsorption of weak polyelectrolytes from aqueous solution. J Colloid Interface Sci 1986 111 446— 454. 

Monolayers as modifiers on electrode surfaces are prepared by sorption techniques. Self-assembled monolayer s (SAMs) form by spontaneous adsorption of precursors on the electrode substrate with an ordered orientation by interaction of certain molecule areas protruding from the sorption plane [109—112] most popular are SAMs prepared by thiol compounds on gold surfaces, but also SAM formation on CPEs is possible. Langmuir-Blodgett layers (LBLs) are monolayers made by surfactants by adsorption from the surface of a solution [113]. Highly ordered multistacked structures from polyelectrolytes can be obtained by layer-by-layer deposition, where the ensuing plane of the stack can be immobilized by sorption of a countercharged polyelectrolyte [114-116]. 

In this chapter I present the current state of three aspects in physicochemistry of nanoparticles critical for understanding structure and properties of nanocomposites. This also relates to adsorption and chemisorption of macromolecules on nanoparticle surfaces from solutions the generation of interfaces phenomena of surface conductivity and specific interactions that depend on the chain origin and length, its conformation, the composition of copolymers and so on. In polyelectrolytes similarly charged with nanoparticles, hydrophobic polymers are inclined to associate ionic groups and form domains as microphases of ion regions. 

The main processes by which particles dispersed in a liquid can acquire a surface charge are (1) preferential adsorption of ions, (2) dissociation of surface groups, (3) isomorphic substitution, and (4) adsorption of charged polymers (polyelectrolytes). Preferential adsorption of ions from solution is the most common process for oxide particles in water, whereas isomorphic substitution is commonly found in clays. The adsorption of polyelectrolytes is the main charging mechanism in electrosteric stabilization and will be discussed later. The dissociation of ionizable... 

The Adsorption (qv) of polyelectrolytes from solution onto solid, liquid, or gas interfaces defines a vast field, one that encompasses innumerable phenomena and many technologies. To simplify, only the grossest and most common issues are introduced here (268-270). Figure 20 displays pictorially how flexible polyelectrolyte homopolymers interact with a flat, charged surface (269). The left-hand side of this cartoon indicates behavior at low Cg, a condition typically dominated... 

The polyelectrolyte multilayer films were prepared using the layer-by-layer (LbL) technique of electrostatically driven sequential adsorption of polyions from their solutions. The technique is described in details elsewhere [1,17]. Adsorption of polyelectrolytes was performed from solutions of NaCl in H2O of concentration 0.15 M at PE concentration of 0.5 g/1. Each deposition step lasted 20 min and rinsing in between the steps was done 3 times for 2 min in water. Always ultra pure water with Milli-Q quality was used. Ready samples were rinsed with D2O before the NR experiments. 

In this review, we have summarized theoretical concepts and recent advances for the adsorption of linear polyelectrolyte molecules onto curved surfaces in the weak and strong adsorption limit. A mean-field description is adopted, and the interaction potentials between the polyelectrolyte and the surfaces are derived from the linearized Poisson-Boltzmann equation for the corresponding geometries (planes, cylinders, and spheres). The derivation of an exact analytical solution of the adsorption problem for curved surfaces is a major challenge and is yet unsolved. 

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