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, T g,α. The slow water process was thought to exist only in aqueous solutions of polymers with high T g,α. However, the m process exists in low-T g,α PVME–water mixtures. With decreasing temperature, the strength of the ν process, Δεν, increases above 200 K (cross over temperature, T c), decreases below T c, and is nearly constant below T g,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 T c being higher than T g,α, a fraction of the fast motion of water gradually changes to the slow one from T c to T g,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 (T c) and T g,α.