Dielectric relaxation processes in water mixtures of tripropylene glycol.

Broadband dielectric measurements for anhydrous tripropylene glycol (3PG) and 96, 92, 84, 80, 74, 71, and 68 wt % 3PG-water mixtures are performed in the frequency range of 10^-2–10⁷ Hz and in the temperature range of 123–243 K. We examined the effect of adding water into anhydrous 3PG on relaxation dynamics. Apart from the two well-known relaxation processes, i.e., α and β for anhydrous 3PG we observed new relaxation peak (β^′) for all aqueous mixtures of 3PG. In addition we found the critical mole fraction of water x_w=0.67 in which relaxation dynamics changes its behavior. According to the Sudo approach [S. Sudo et al., J. Non-Cryst. Solids 307–310, 356 (2002)], the behavior of relaxation processes was interpreted assuming the existence of three kinds of cooperative domains (CDs): containing only 3PG molecules, including only water molecules, and including both 3PG and water molecules, which molecules of each kind CD are bound by hydrogen bonds. [ABSTRACT FROM AUTHOR]