Besides the fast translational diffusion of individual chains,, a slow telaxation, mode is frequently Observed in dilute poly(ethylene Oxide) (PEO) aqueous sohitions in dynamic laser light scattering (LLS) experiments, which Was attributed to some hydrophobic impurities in PEO or interchain association. Recently, we also encountered such a slow mode- When studying,dilute Solutions of star-like PEO chain S in Water, hindering our fiuther study of their dynamics in semidilute solution. Using a combination of static and dynamic- US, we found that the slow mode is removable after repeated filtration through a hydrophilic 0.45 mu m. PTPE filter or heating at 55 degrees C, resulting in a stable solution with only one fast translational mode of individual chains even after 5 months. Further, we found that an injection Of a small anionnt of air regenerated the slow mode, revealing its origin) small air bubbles stabilized by the pEo chains adsorbed a the air/water interface, not previously proposed impurities or equilibrium -betWeen large interchain aggregates arid individual chains. Our result has clarified a long-standing confusion of whether PEO is completely soluble in water as individual chains at room temperature.- Out fincling is, impOrtant -"since -aqueous solutions-, of PEO and its copolymers are widely used as model systems in academic research and as important ingredients in various industrial applications.