HYDRODYNAMIC THICKNESS AND DEFORMATION OF ADSORBED LAYERS OF POLYETHYLENE OXIDES

From measurement of surface potentials of quartz capillaries before an d after adsorption of PEO of various molecular masses, an assessment o f the equilibrium hydrodynamic thickness of adsorbed layers delta has been obtained. When delta values are calculated with the Gouy equation , the psi(10) potentials of the quartz surface under the adsorbed laye r of PEO are used. The zeta potentials measured at a very low concentr ation of the polymer solution, 10(-4) g/dm(3), were adopted as the phi (10), values. This method gives data that coincide better with the res ults of independent measurements of delta. The flow of polymer solutio n under increasing pressure differences causes deformation of adsorbed PEO layers, which manifests itself in changes in hydrodynamic thickne ss. The delta values decrease by 2-3 times when the tangential shear s tress tau increases to 200 N/m(2). Such high values of tau were realiz ed by using thin capillaries, 5-6 mu m in radius, and by applying the capillary electrokinetics method. (C) 1995 academic Press, Inc.