Adsorption studies of polyethers - Part II: adsorption onto hydrophilic surfaces

The adsorption of BAB-type triblock copolymers (B = poly(ethylene oxide); A = poly(propylene oxide)) from aqueous solution onto hydrophilic silica par ticles is described with particular reference to the role of the copolymer composition. The adsorbed amount and the layer thickness were determined by the standard depletion method and photon correlation spectroscopy, respect ively. Snowtex-YL silica was used as the adsorbent. The results show an inc rease in the adsorbed amount with increasing molar masses of both PEO and P PO blocks. The adsorbed layer thickness is found to depend strongly on PEO block mass. Both these parameters (adsorbed amount and hydrodynamic layer t hickness) show a maximum as a function of the mole fraction of the PPO bloc k present in the copolymer. The conformation of the adsorbed layer is deter mined by the surface-copolymer interaction; principally by the interaction of the hydrophilic PEO block with the silica surface. A good qualitative ag reement of the experimental results with theoretical predictions and self-c onsistent mean field calculations has been found. (C) 1999 Elsevier Science B.V. All rights reserved.