STATIC AND DYNAMIC PROPERTIES OF POLY(ETHYLENE OXIDE) IN METHANOL

The properties of polyethylene oxide) PEO chains in dilute and semidilute solutions in methanol have been examined using pulsed-field-gradient NMR and static and quasielastic light scattering (QELS). From the temperature dependence of the second viral coefficient the θ temperature was determined to be close to 16.7 °C. Values of the inverse osmotic compressibility (∂r/∂C), determined independently from static LS and the ratio of the respective diffusion coefficients (DQELS/DNMR) in dilute solution, were identical within experimental uncertainty and are precisely described by renormalization group theory. The latter also provides a good fit for the concentration dependence of the diffusion coefficient. The self-diffusion coefficients are represented by a universal curve: log (D/D0) versus log (C/C*). The dynamic light-scattering measurements showed the presence of molecular clusters (or ordered domains), which appear to constitute a general feature of PEO solutions in both good and poor solvent quality. These clusters diminish in size as the temperature is raised and/or the concentration is lowered. Data for hard spheres (stearic acid coated Si02) diffusing in the PEO solutions formed a universal curve, log (D/D0) versus log (C/C*), independent of sphere size and gave a dependence on matrix MW M−0·58. Clusters of size similar to the hard spheres have an apparent diffusion rate that is 1 order of magnitude slower at the same matrix polymer concentration. © 1990, American Chemical Society. All rights reserved.