Polycationic electrolytes

Figure 6.37 Conditions in bulk and surface of solution containing a polycationic electrolyte and anionic surfactant. The full line of curve is the hypothetical surface tension concentration plot of the surfactant alone dashed line is that of mixture with polycation. Simple gegen-cations are depicted only in the surface zone. From Goddard et al. [267].

The polymers are obtained directly in a conductive polycationic form in which charge-compensating counter anions from the electrolyte system are intercalated... 

The wall of the silica column is lined with silanol groups that become de-pro tonated when the pH is above 2. Under these conditions, a fixed polyanionic layer is formed (Fig. 8.5). However, a polycationic layer due to the electrolyte acts as its counterpart. The H30+ ions and electrolyte cations are put in motion when the electrical field is applied. The net effect is to make all the species present migrate towards the cathode. This linear displacement of the electrolyte, which originates from the charge carried by the electrolyte ions and tangential applied electrical field, can be controlled or reversed by modifying the capillary inner surface, the pH, or by adding cationic surfactants. 

The [Ru(NHs)5 pyridine]2+/3+ redox center exhibits well-defined, nearly ideal voltammetry across a wide range of electrolyte compositions, scan rates and temperatures. Despite the headgroups having comparable sizes, the saturation surface coverage is less than that found for ferrocene alkane thiol monolayers. This behavior is thought to reflect electrostatic repulsion between the polycationic redox centers and the need to incorporate counterions into the monolayer in both... 

Electrically conducting polymers are quite different systems to the above elec-troinitiated chain polymerizations since they are formed by an unusual step-growth mechanism involving stoichiometric transfer of electrons. The polymers are obtained directly in a conductive polycationic form in which charge-compensating counter anions from the electrolyte system are intercalated into the polymer matrix [173], Exact mechanistic details remain the subject of discussion, but Scheme 4, which shows polypyrrole formation is plausible. Polythiophene is similar where S replaces NH in the ring. 

Over the past 10 years, research into water-soluble ferrocene-based polymers and polyelectrolytes has increased.168-175 Vancso and co-workers have reported the preparation and self-assembly of anionic and cationic polyelectrolytes.171,172 Polyanionic, 89, and polycationic, 90, ferrocene-based electrolytes are two examples of such polyelectrolytes.170... 

A polyion in the form of a thin membrane is used as ion-exchange membrane in another application of the ion-exchange phenomenon. When exposed to an electrolyte, an ion-exchange membrane will allow counterions to pass through it, but will act as a barrier to the complementary ion, and is therefore said to be permselective. Thus a polyanionic membrane will allow passage of cations and a polycationic membrane that of anions, so that under the influence of an electric current, continuous fluxes of cations and anions, respectively, can be set up across these membranes. This principle is exploited in electrodialysis and in chlor-alkali cells as described later. 

The polycationic chitosan can also dissipate the negative surface charge on cotton and drives dye molecules to the fiber. Such effects can be studied by comparing the dyeing results of chitosan-treated samples conducted in electrolyte-free dye bath with that in presence of electrolyte. The progressive decrease in importance of sodium sulfate taken as electrolyte with increase in chitosan concentration, as shown in Figs. 19.26 and 19.27, clearly elucidates the role of chitosan in the improvement of dye uptake even at reduced electrolyte concentration. 

Considerable attention has been directed toward the synthesis of water-soluble ferrocene-based polymers and polyelectrolytes. Vancso and coworkers reported flie synthesis and self-assembly of anionic and cationic polyelectrolytes. Scheme 55 shows tile strategy that was apphed by Manners and coworkers in the design of polyanionic (189) and polycationic (190) water-soluble ferrocene-based electrolytes. ... 

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