Surface modification of polystyrene nanoparticles using dextrans and dextran-POE copolymers: polymer adsorption and colloidal characterization.
Hydrophobically-modified dextran (dextran-phenoxy, DexP) and dextran-phenoxy-poly(oxyethylene) (DexP-POE) copolymers have been used to modify the surface properties and the stability of polystyrene nanoparticles. We examined the effect of phenoxy group and POE chain concentrations on their adsorption behaviour. The adsorbed amount was determined by the standard depletion method and the layer thickness of the adsorbed layer by photon correlation spectroscopy and electrokinetic measurements. The results show that the hydrophobic interaction is the driving force during the adsorption while the layer thickness correlates with the interfacial concentration of grafted POE chains. The effects of adsorbed layers on the properties of latex dispersions have been characterized in terms of the stability of the dispersions toward added electrolyte and temperature. The conformation of the adsorbed copolymers is discussed in relation to layer thickness and colloidal stability of suspensions.