Charge density parameter, cationic polyelectrolyte

The present review deals mainly with two examples of polyelectrolyte phase behavior as discussed above. As an example for an H-type precipitation, the solution properties of polyvinylpyridinium chains are monitored as function of added inert salt. Here, we focus on the determination of the effective charge density and of the solvent quality parameter which are supposed to play a central role for the understanding of polyelectrolyte solution without specific counterion interactions. The second system under investigation comprises the interaction of polyacrylic acid with alkaline earth cations which exhibit very specific interactions, thus representing an example for type L-precipitation. Here the coil dimensions close to the phase boundary are compared to those close to type H-precipitation with inert added salt. 

Figure 5.39. Theoretical (a) and experimental (b) amount adsorbed as a function of the salt concentration for polyelectrolytes of varying charge density a, as Indicated. The theoretical figure was calculated for 0-6 and a surface charge density

Abstract Two types of membrane are presented free-standing films which are formed from aqueous polyelectrolyte solutions and membranes prepared by alternating electrostatic layer-by-layer assembly of cationic and anionic polyelectrolytes on porous supports. Layer-by-layer assemblies represent versatile membranes suitable for dehydration of organic solvents and ion separation in aqueous solution. The results show that the structuring of the polyelectrolytes in the liquid films and the permeability of the multilayer membranes depends on different internal and environmental parameters, for example molecular weight, polymer charge density, ionic strength, and temperature. 

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