ASYMPTOTIC-BEHAVIOR AND LONG-RANGE INTERACTIONS IN AQUEOUS-SOLUTIONS OF POLY(ETHYLENE OXIDE)

Static and dynamic light scattering measurements of single-chain behavior reveal that, even for the readily accessible molecular weight range 10(5)-10(6), poly(ethylene oxide) (PEO) in water at 30-degrees-C exhibits asymptotic good solvent behavior both for the equilibrium parameters A2 and R(g) as well as for the dynamic parameters R(h) and k(D). Moreover, it is shown that PEO coils are larger and PEO coil-coil interactions stronger than those found for typical polymer coils in organic solvents. It is concluded that the unusually large size and long range of PEO coil-coil interactions in water are due to the unusual ability of water molecules to "pack" into and swell coils along with a general structuring of water in the PEO/H2O system, respectively. It is further noted that while observed k(D) values are typical of those expected in a good solvent, these values cannot be rationalized in terms of theories that treat coil-coil interactions in good solvent solely in terms of "equivalent hard-sphere" interactions.