Absorbed polyelectrolytes

This type of membrane is rather rare, as two requirements must be satisfied the amount of absorbed polyelectrolyte must be high to get a good selectivity, and the leaching-out must be negligible. 

CGE is suitable for the analysis of synthetic polyelectrolytes. Fast separations of high repeatability-when analyte interactions with the capillary wall are excluded-help to decrease separation time and solvent consumption compared with SEC. The only restriction is that CGE is only an analytical technique for small sample sizes. Selection of the optimal separation system with respect to molecular mass of the sieving polymer and its concentration is possible by applying simple rules and available data like intrinsic viscosity of potential sieving polymers. Non-UV-absorbing polyelectrolytes can be analyzed by applying indirect detection techniques. In various applications it has been shown that determination of molecular mass averages and molecular mass distribution is possible with CGE. 

Waldron-Edward D, Thyvalikakath PM, Skoryna SC. 1965b. Suppression of intestinal absorption of radioactive strontium by naturally occurring non-absorbable polyelectrolytes. Nature 205 1117-1118. 

Polyelectrolytes Linear polyelectrolytes in solution can provide a scaffold for the adsorption of metal ions with opposite charges. Thereafter, the ion-absorbed polyelectrolyte templates can transform to ID metal or semiconductor NP assemblies either by a reduction reaction or by chemical combination of ion pairs. Minko and co-workers explored this strategy to prepare 1D Pd NP assemblies. Colfen and co-workers adopted double-hydrophihc block copolymers (DHBCs) with more complex structures, in which one hydrophilic block interacted strongly with appropriate inorganic materials and the... 

As well as producing repulsion by introducing a polymer onto the surface of the particles, one can combine both effects using absorbed polyelectrolytes, i.e. polymers with charge distributed along the chains. The particular nature of the forces arising is different in each case but the overall effect is always the same—they produce a repulsive force. We need say no more about normal polymers at this stage with respect to the details of these force, but it is useful to note that the... 

O Brien, R.W. (2002) The effect of an absorbed polyelectrolyte layer on the dynamic mobility of a colloidal particle. Particle ej Particle Systems Characterization, 19, 186-194. 

Salt effects in polyelectrolyte block copolymer micelles are particularly pronounced because the polyelectrolyte chains are closely assembled in the micellar shell [217]. The situation is quite reminiscent of tethered polymer brushes, to which polyelectrolyte block copolymer micelles have been compared, as summarized in the review of Forster [15]. The analogy to polyelectrolyte brushes was investigated by Guenoun in the study of the behavior of a free-standing film drawn from a PtBS-PSSNa-solution [218] and by Hari-haran et al., who studied the absorbed layer thickness of PtBS-PSSNa block copolymers onto latex particles [219,220]. When the salt concentration exceeded a certain limit, a weak decrease in the layer thickness with increasing salt concentration was observed. Similar results have been obtained by Tauer et al. on electrosterically stabilized latex particles [221]. 

In this article I review some of the simulation work addressed specifically to branched polymers. The brushes will be described here in terms of their common characteristics with those of individual branched chains. Therefore, other aspects that do not correlate easily with these characteristics will be omitted. Explicitly, there will be no mention of adsorption kinetics, absorbing or laterally inhomogeneous surfaces, polyelectrolyte brushes, or brushes under the effect of a shear. With the purpose of giving a comprehensive description of these applications, Sect. 2 includes a summary of the theoretical background, including the approximations employed to treat the equifibrium structure of the chains as well as their hydrodynamic behavior in dilute solution and their dynamics. In Sect. 3, the different numerical simulation methods that are appHcable to branched polymer systems are specified, in relation to the problems sketched in Sect. 2. Finally, in Sect. 4, the appHcations of these methods to the different types of branched structures are given in detail. 

Although cellulose acetate is not inherently a polyelectrolyte there are reports which indicate that it contains a low concentration of weak acid, presumably carboxylic, groups (1). Water absorbed by cellulose acetate membranes might be preferentially located, to some extent, in the region of these ionogenic groups and so assist in their dissociation. 

By electropolymerization of pyrrole in solvents containing polyelectrolytes such as potassium polyvinylsulfate, it is possible to prepare films of polypyrrole with polymeric counterions which have good conductivity (1-10 S cm-1) and strength (49 MPa) 303 304,305). Such a material could be used reversibly to absorb cations in an ion exchange system. Pyrrole has also been electrochemically polymerized in microporous polytetrafluoroethylene membranes (Gore-tex), impregnated with a perfluorosulphonate ionomer 3061. 

Synthetic polyelectrolytes can be separated by capillary electrophoresis applying the same rules derived for the electrophoresis of biopolymers. In the reptation regime, determination of the molecular mass and polydispersity of the polyelectrolytes is possible. Introduction of chromophores facilitates the detection of non-UV-absorbing polymers. Indirect detection techniques can probably be applied when analytes and chromophores of similar mobilities are available. 

Figure 6.4 Optical absorbance of pure silver NPs, (A), gold / silver alloy NPs, (dashes) and pure gold NPs (solid line) coated onto polyelectrolyte coated microplate wells analysed under ambient conditions. Forty eight wells were examined in total, sixteen for each NP.

In this section, we want to present some recent results which have been obtained by B. Mann using ESPResSo, and explain, how this has been done [41,43,47]. The system under investigation is a polyelectrolyte network, i.e. a gel of cross-linked charged pol uners. One of the most prominent features of such a network is that it is able to absorb large amounts of the solvent, up to several hundred times its dry mass. Due to its remarkable properties, this hydrogel has many industrial applications, e.g. as superabsorbants in diapers,... 

The test device for specific gravity consists of an absorbent cellulose pad impregnated with bromthymol blue, poly-methylvinyi ether and/or maleic anhydride, and sodium hydroxide. The test depends on the apparent pK change of the pretreated polyelectrolyte in relation to ionic strength the hydrogen ions released are detected by the pH indicator. The color changes from a dark blue at a low specific gravity... 

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