APPARENT AGGREGATION BEHAVIOR OF POLY(ETHYLENE OXIDE) IN WATER AS A RESULT OF THE PRESENCE OF AN IMPURITY

Poly(ethylene oxide) does not aggregate in dilute water solutions. The slow-mode behavior frequently observed by dynamic light scattering fr om poly(ethylene oxide) solutions in water already below and around th e coil overlap concentration, often interpreted as the onset of semidi lute behavior and/or clustering, is shown to be a result of the presen ce of an impurity. The impurity may be conveniently described as micro droplets or compact microparticles, sterically stabilized by the prese nce of poly(ethylene oxide) macromolecules, formed from a hydrophobic organic substance sparingly soluble or insoluble in water and increasi ngly soluble in methanol and collected within samples at the ppm level during their whole history. A solid phase extraction mechanism govern s the successful removal of the impurity from poly(ethylene oxide)-wat er solutions when hydrophobic filters are used.