The adsorption isotherm of a hydrophobically modified inulin (INUTEC SPI) on polystyrene (PS) and poly(methyl methacrylate) (PMMA) particles was determined. The results show a high affinity isotherm for both particles as expected for a polymeric surfactant adsorption. The interactions forces between two layers of the hydrophobically modified mulin surfactant adsorbed onto a glass sphere and plate was determined using a modified atomic force microscope (AFM) apparatus. In the absence of any polymer, the interaction was attractive although the energy of interaction was lower than predicted by the van der Waals forces. The results between two layers of the adsorbed polymer confirms the adsorption isotherms results and provides an explanation to the high stability of the particles covered by INUTEC SPI at high electrolyte concentration. Stability of dispersions against strong flocculation could be attributed to the conformation of the polymeric surfactant at the solid/liquid interface (multipoint attachment with several loops) which remains efficient at Na2SO4 concentration reaching 1.5 mol dm-3. The thickness of the adsorbed polymer layer in water determined both by AFM and theology measurements, was found to be about 9 nm. (c) 2007 Elsevier Inc. All rights reserved.