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A combination of viscometry, Raman scattering and 'H NMR measurements has been used to study the effect of temperature changes on the properties of solutions of poly(ethy1ene oxide) in H 2 0 or D20. The viscosity data show that the overall dimensions of the polymer chains decrease with increasing temperature, while the Raman spectra indicate a simultaneous decrease in chain helicity. Polymer 'H NMR spin-lattice relaxation times, in D 2 0 are consistent with a mechanism in which small segments of the chain reorient at a rate controlled by the solvent viscosity up to a temperature of ca. 80°C.

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Differential scanning calorimetry has been used to investigate the melting behaviour of mixtures of poly(ethy1ene oxide) and deuterium oxide. The phase diagram shows that a eutectic mixture is formed with a weight fraction of D 2 0 of 0.57 and a melting point of 264 K. A change in the curvature of the polymer liquidus curve occurs when the ratio of D, O to EO repeat unit is 1.2. For higher water contents the liquidus curves can be fitted by the Flory-Huggins theory. Enthalpies of fusion have been used to calculate the enthalpy of mixing of the two components at 264 K. A maximum exothermicity is found for a D,O/EO ratio of 1.3 & 0.1. Quenching of mixtures with either high or low water contents in liquid nitrogen produces glassy polymer which undergoes devitrification and cold crystallization on heating. Plots of the enthalpies of cold crystallization against weight fraction of D,O indicate that the maximum amount of glass is formed at a D20/E0 ratio of 0.9 f 0.3. It is concluded that the average hydration number of the EO group is approximately one.