State Analysis of Water in the Macromolecule of Polyol Studied by the New High-Frequency Spectroscopy

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Water molecules contained in polyethylene oxide (PEG) have been analysed mainly by high-frequency spectroscopy. The hydrophilicity of PEG comes from the two lone pairs of oxygen atom in ethylene oxide (EC) unit. Two water molecules may directly be attached to the EO oxigen, so that the behavor of water molecules bound to PEO would be varied for samples with different EO : H_2O ratio especially arround 1 : 2. The restrained character of the water molecules in PEO has been found to be divided into four regions of EO : H_2O ratio from the analysis of high-frequency spectra. In region 1 (EO : H_2O=1.0〜1.25), the water molecules are not associated to each other, but strongly bound to the EO oxygen atoms. In region 2 (EO : H_2O=1.25〜2.0), water molecules are bound to the EO oxygen, and at the same time they are associated to each other by hydrogen bonding. In region 3 (EO : H_2O=2.0〜10.0), almost all the water molecules are associated to each other, with bound character to some extent. In region 4 (EO : H_2O=100〜), the character of water molecules in PEO are very close to that of bulk water (or freezable water).