ABSTRACT
It is possible to displace PEO of low molar mass by PEO of high molar mass from the silica surface. This is demonstrated by the hydrodynamic thickness. If PEO 900,000 is added to silica fully covered with PEO 50,400, the layer thickness increases within 10 min to nearly the same value as at direct addition of PEO 900,000 [168]. A reduction of the thickness with time is measured with PEO layers of high molar mass. The reduction becomes lower with increasing excess of the polymer in solution and upon a critical excess concentration a time-independent thickness become existent (Fig. 30). Two reasons, polymer degradation and reorganization of the polymer layer, may be responsible. The existent time-dependent flocculation by bridging is a hint for the change of the layer structure in a period of hours.
