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Abstract
It can be shown that poly-(ethylene oxide) in its monomeric form, at molecular weights greater than about 1,000, cannot be soluble in water. Nonetheless, in actual practice poly-(ethylene oxide) is widely used for its hydrophilicity and for its unlimited aqueous solubility. The explanation for this apparent contradiction lies in the fact that poly-(ethylene oxide) molecules form a nonionic surfactant of a novel category, with its hydrophilic and hydrophobic chains attached to each other over their entire length so that its hydrophilic ethylene oxide side is exposed to the water interface while the hydrophobic poly-(ethylene) side remains hidden thanks to the formation of micelles.
Notes
Shown are the free energies of interaction values for ΔGEO-W-EO [two poly-(ethylene oxide) sides, EO, both immersed in water]; for ΔGPE-W-PE [two poly-(ethylene) sides, PE, both immersed in water] and ΔGEO-W-PE [one poly-(ethylene oxide) side, EO, and one poly-(ethylene) side, PE, both immersed in water. When ΔG is positive, the interaction is repulsive and when ΔG is negative, the interaction is attractive.