Moderation of the interactions between sodium dodecyl sulfate and poly(vinylpyrrolidone) using the nonionic surfactant hexaethyleneglycol mono-n-dodecyl ether C12EO6:: an electromotive force, microcalorimetry, and small-angle neutron scattering study

The polymer-surfactant complex formed between sodium dodecyl sulfate (SDS) and poly(vinylpyrrolidone) (PVP) contains SDS micelles bound to the polymer chain. When a PVP sample of MW 360 000 is saturated with SDS micelles, the complex is a beadlike structure with the PVP wrapped around 25 SDS micelles. The bound SDS was systematically removed from the polymer chain by the addition of the nonionic surfactant hexaethylene glycol mono-n-dodecyl ether, C12EO6, and this process was monitored using isothermal titration calorimetry (ITC). Electromotive force, emf, measurements carried out with a dodecyl sulfate electrode were also used to monitor the desorption of bound SDS from the polymer chain via the SDS monomer concentration. Furthermore, these measurements showed that during the removal of SDS from the polymer, mixed SDS/C12EO6 micelles were formed both on the polymer chain and in solution. The structure and composition of these mixed micelles were determined using small-angle neutron scattering (SANS). The data indicate that electrostatic interactions are the main factor influencing the binding.