Polyelectrolytes counterion interactions, solution-based

SANS is an alternative technique in which contrast can be achieved through the use of deuterated counterions. A number of systematic SANS studies have been performed by Groenewegen et al. who studied suitable block copolymers in aqueous solution. These block copolymers build up micelles with a hydrophobic core and a corona consisting of polyelectrolyte chains. To enhance the contrast, deuterated counterions based on quaternary ammonium salts were used. However, the exchange of counterions or bulky hydrophobic counterions to be used in SANS experiments may lead to specific effects that may become as important as electrostatic interaction. 

Alternatively, UCST behavior in water can be achieved based on the interactions between a polyelectrolyte with multivalent counterions as has been described for solutions containing poly(dimethylamino ethyl methacrylate) with the trivalent anion [Co(CN)g] (Plamper et al, 2007). Despite the hydrogelation of polyelectrolytes in the presence of multivalent ions being commonly known, such as the gelation of alginate in the presence of calcium(II), there are few studies focusing on the UCST type phase transitions of such hydrogels or polymer solutions. The synthesis of such vinyl polymers can be performed by radical polymerization, as discussed in Section 2.3.1. 

Addition of sodium, potassium, calcium, ammonium, etc., bases to aqueous solutions of Gantrez AN resins leads to two viscosity peaks, corresponding to 1 and 2 mole equivalents of base. The interpolymers are precipitated by Ca ions and other heavy, polyvalent metal cations, beyond 0.7 mole equivalents. With ammonium hydroxide, peaks tend to be observed at about 1 and 3 mole equivalents of base. Ionic interactions in aqueous solutions of Gantrez AN polyelectrolytes and polycarboxylates, electrophoretic mobility and viscosity of copolymer salts, counterion binding properties, etc., have received substantial <659,672.700-702,1100) polyelectrolyte salt sol-... 

The existing theoretical models may be characterized by the number of dynamic components (polyions, co-ions, counterions) being considered explicitly. One-component theories most closely resemble the theories developed for neutral polymer solutions. A rationale for using this approach is that, in the limit of vanishing electrostatic interactions, polyelectrolytes behave as neutral polymers. On the other hand, multi-component theories are based on models developed for low molecular weight electrolytes. This approach is most powerful for strong electrostatic interactions, where polymer effects are less important. 

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