Surfactant/Polymer Assemblies. 2. Polyelectrolyte Properties

The polyelectrolyte nature of the aggregates formed between neutral polymer, poly(vinyl pyrrolidone) (PVP) and anionic surfactant, sodium dodecyl sulfate (SDS) is demonstrated via their light scattering behavior. Adding SDS to neutral PVP is similar to electrostatically charging a neutral polymer, thereby increasing electrostatic excluded volume effects and decreasing osmotic compressibility and light scattering. Similarly, once formed, the behavior of these aggregates with respect to ionic strength resembles that of normal linear polyelectrolytes; namely, increasing ionic strength decreases their interactions, as measured by A 2, and decreases their R g. Using combined electrostatic persistence length and excluded volume models, the main features of these phenomena are semiquantitatively described. Because SDS exists in multiple equilibria in the PVP/SDS solutions, the system is more complex than normal linear polyelectrolytes, and so the PVP/SDS aggregates also evidence behavior distinct from traditional polyelectrolytes.