Behavior of Bound Water in Polyethylene Oxide Studied by DSC and High-Frequency Spectroscopy

Measurements of DSC, NMR and high-frequency spectroscopy have been done on PEO-H 2 O and PEO-H 2 O-HQ mixed systems. DSC measurements show that water molecules contained in PEO are divided roughly into two species: freezable water and non-freezable water. By 1 H-NMR measurements, PEO and H 2 O protons show an absorption peak around 3.6 ppm and 4.5 ppm, respectively. All the PEO-H 2 O samples containing H 2 O show NMR absorption signals, suggesting the existence of movable H 2 O. Samples with H 2 O molar ratio over 0.5, show one absorption peak of H 2 O protons, and more than two peaks of PEO. The results from DSC and NMR measurements show that the bound state of H 2 O in PEO, as well as the mobility of PEO itself, varies according to the water content in PEO-H 2 O samples. On the other hand, DSC measurements give the result that PEO-H 2 O-HQ systems can be considered as homogeneous so long as the content of H 2 O and/or HQ is not so high. Furthermore, the water molecules in the system exist as bound water. Results of high-frequency spectroscopic measurements for the PEO-H 2 O and PEO-H 2 O-HQ systems show good agreement with those of DSC and NMR measurements.