Equilibrium and kinetic studies associated with the interaction between sodium dodecyl sulfate and polyvinylpyrrolidone in aqueous solution

Binding isotherms for various sodium dodecyl sulfate–polyvinylpyrrolidone mixtures have been constructed from electrochemical measurements involving a dodecyl sulfate-selective membrane electrode. It was found that once the surfactant starts to bind to the polymer, small surfactant aggregates are formed. These aggregates grow in size until the polymer becomes fully saturated after which ‘free’ micelles are formed in solution. The degree of counterion dissociation was also measured using an electrode selective to the sodium counterion. The surfactant concentration at the start of binding and at the onset of the formation of free micelles was also determined using gel filtration. Finally the kinetics of the binding process were measured using ultrasonic relaxation measurements.