In
this study, we investigated the cooperative molecular dynamics
of poly(vinylpyrrolidone) (PVP), ice, and uncrystallized water (UCW)
in partially crystallized PVP–water mixtures by means of broadband
dielectric spectroscopy. Three relaxation processes, denoted I, II,
and III, were observed at temperatures ranging from immediately below
the crystallization temperature (T
c) to
approximately 200 K. At temperatures of 173–193 K, processes
I and II cannot be distinguished. Below 168 K, process II separates
into two processes: process IV at higher frequencies and process V
at lower frequencies. Process I contributes to process V. In partially
crystallized mixtures, process I originates from UCW in an uncrystallized
phase with PVP. Process II is attributed to ice in the mixture, with
a relaxation time that is 2 orders of magnitude smaller than that
of pure ice. The concentration dependence of the strength of process
II and the relaxation time relative to that of ice in bovine serum
albumin (BSA)–water and gelatin–water mixtures strongly
support this conclusion. Observation of processes IV and V indicates
the presence of multiple ice relaxation processes. Process III is
attributed to the α process of PVP in the uncrystallized phase
in 40 and 50 wt % PVP mixtures. For mixtures with 30 wt % PVP or less,
process III is attributed not only to the α process of PVP but
also to interfacial polarization.