Interactions of Star Polymers with Surfactants

Abstract

Binding isotherms between star poly(ethylene glycol) (s-PEG) and the anionic surfactant sodium dodecyl sulfate (SDS) have been measured. The onset of SDS/s-PEG binding happens at the same concentration for both star and linear PEG, but saturation of the star occurs at a lower surfactant concentration. The size of the star has been measured as a function of SDS concentration by NMR self-diffusion and small-angle neutron scattering (SANS) techniques. The star decreases in size at the normal critical micelle concentration (CMC) of the SDS but increases at higher SDS concentrations. These results echo the findings of photocorrelation spectroscopy and SANS studies on physically adsorbed PEG on polystyrene latex. At high surfactant concentrations the star adopts an elongated conformation. The surfactant binds to the star molecules in the form of spherical micelles, which are of similar size to free solution micelles.