Dielectric Relaxations of Polymer and Primary and Slow Water in Water Mixtures of Poly(vinyl methyl ether) as a Polymer with Low Glass Transition Temperature

Broadband dielectric spectroscopy measurements were performed on dry poly(vinyl methyl ether) (PVME) and PVME–water mixtures with PVME concentrations in a range of 60–98.7 wt % at temperatures ranging from 123 to 323 K using purified PVME. At high, low, and intermediate frequencies, three relaxation processes of ν, α, and m were observed simultaneously. The ν process is the primary relaxation of water originating from the local motion of water. The α process originated from the segmental chain motion of PVME. The α process has properties similar to those of polymers in nonpolar solvents. The m process is similar to the slow water process observed in the aqueous solutions of poly(vinylpyrrolidone) (PVP), ε-poly(l-lysine), trilysine, and dextran, which are the polymers with high glass transition temperature of the α process, Tg,α. The slow water process was thought to exist only in aqueous solutions of polymers with high Tg,α. However, the m process exists in low-Tg,α PVME–water mixtures. With decreasing temperature, the strength of the ν process, Δεν, increases above 200 K (cross over temperature, Tc), decreases below Tc, and is nearly constant below Tg,α. This temperature dependence is similar to that observed in aqueous solutions of molecular liquids (e.g., fructose and ethylene glycol oligomers). According to a comparison among the water mixtures of PVP, molecular liquid, and PVME, in the mixtures with Tc being higher than Tg,α, a fraction of the fast motion of water gradually changes to the slow one from Tc to Tg,α. The variation of the temperature dependence of Δεν appears to be due to the relationship between the onset temperature of the slow dynamics of water (Tc) and Tg,α.