Interaction between polymer microgels and ionic surfactants.

The interaction between poly(N-isopropylacrylamide) microgel latex and sodi um dodecyl sulfate was investigated by dynamic light scattering, electropho retic mobility measurements and by determining the binding isotherm of the surfactant. The interaction starts from a critical surfactant concentration and takes place in two binding steps. In the first step the surfactant bin ds at the shell of the microgel particles in form of small aggregates follo wed by binding in the core of the particles. The stepwise surfactant bindin g is a consequence of the inhomogeneous inner structure of the microgel par ticles.