Because of the dissociation of the ionic groups a high number of low molecular counterions per macromolecule is present in solution and strong electrostatic interactions between all species occur, causing disturbances in all methods of characterization. While investigations at low salt contents or in salt-free solutions are of great interest to study the special polyelectrolyte effects, the interactions can be suppressed by addition of a sufficient amount of low molecular salt. This offers the possibility to use all methods, well-known in the macromolecular characterization of neutral polymers, also for polyelectrolytes. Thorough dialysis and freeze drying are necessary prerequisites for a reliable characterization. Light scattering experiments require often complicated clarification procedures of repeated filtration and preparative centrifugation to eliminate traces of particulate material.
Comprehensive experience exists in characterization of different polyanions and polycations.
Polyampholytes provoke additional problems due to their tendency of aggregation. The degree of aggregation is mainly controlled by the concentration of the component solutions. Our interest is mainly focused on such systems. Therefore, the main objective must be to discover the general effects and tendencies in these processes. The degree of aggregation is correlated to the concentration of the component solutions.