The puzzle of poly(ethylene oxide) aggregation in water: Experimental findings

Aqueous solutions of poly(ethylene oxide) were investigated using the ultra sonic technique, photon correlation spectroscopy (PCS) and nuclear magnetic resonance (NMR), in a wide range of molecular weight (from ethylene glycol to poly(ethylene oxide) 4 000 000 Da). Ultrasonic data reveal that the mix ing process is not ideal and show that the polymer-water interaction streng th increases with the polymerization degree. PCS and NMR, on the other hand , furnish a free particle diffusion coefficient which satisfies a unique sc aling law from 8000 to 4 000 000 Da and demonstrates the good solvent natur e of water. These experimental findings indicate that polymer-polymer aggre gation processes are not an inherent property of these systems. (C) 1999 Am erican Institute of Physics. [S0021-9606(99)51302-0].