DEFORMATION OF ADSORBED LAYERS OF POLYETHYLENE OXIDE IN FLOW OF AQUEOUS-SOLUTIONS IN FINE CAPILLARIES

From comparative measurements of the surface potential of quartz capil laries before and after adsorption of polyethylene oxides (PEOs) of va rious molecular weights, the equilibrium hydrodynamic thickness delta of the adsorbed polymer layers has been evaluated. After calculating d elta by means of the Gouy equation, the surface potential of the quart z under the PEO layer was determined on the basis of the zeta-potentia l measured at a low PEO concentration, 10(-4) g/liter. The use of this method of calculation improves the agreement between the calculated v alues of delta and the results obtained in independent measurements. F low of the solution, as the pressure drop across the capillary is incr eased, creates a shearing stress tau on the surface of the adsorbed la yer, thus deforming the layer - as manifested in a decrease of the hyd rodynamic thickness. An increase of tau to 2.10(3) dyn/cm2 gives a sev eralfold decrease in the values of delta. Such values of tau can be ac hieved by the use of fine capillaries with a radius of 5-6 mum in expe riments based on a capillary electrokinetic method of measurement.