ADDITIONAL REDUCTION OF SURFACE-TENSION OF AQUEOUS POLYETHYLENE OXIDE (PEO) SOLUTION AT HIGH POLYMER CONCENTRATION

The surface activity of polyethylene oxide in water is studied by measuring the surface tension as a function of polymer concentration. Conventional adsorption behavior is observed at low polymer concentration, but a novel anomalous surface tension reduction behavior is found at high polymer concentration. The self-assembled adsorbed film created at low polymer concentrations behaves similarly to PEO monolayers at the air/water interface. In the high-concentration regime, the additional surface tension reduction is due to the formation of dense PEO layers. The high-concentration adsorption behavior was mimicked by spreading C16H33-PEO-C16H33(CPC) molecules onto a water surface. The CPC molecule is stable even at high surface polymer concentration, because of the anchoring of the C16H33 at the water surface. The correlation of the surface pressure vs. surface area per molecule of a CPC polymer at the air/water interface shows a behavior similar to a PEO monolayer at low surface concentrations, but also shows additional surface tension reduction at high surface polymer concentrations.