Water dynamics in poly(vinyl pyrrolidone)–water solution before and after isothermal crystallization

Dynamics of Uncrystallized Water, Ice, and Hydrated Polymer in Partially Crystallized Poly(vinylpyrrolidone)–Water Mixtures

“…As mentioned above, PVP−water mixtures have been widely investigated in amorphous states at subzero temperatures 1,4,5 and in the liquid state at temperatures around T c . [9][10][11]29,30 Therefore, this study complements previous research by focusing on the dynamics of a partially crystallized system.…”

“…15−17 Additionally, in partially crystallized gelatin−water mixtures, 16,17 an activation energy (E a ) of 50 kJ/mol has been observed at temperatures below T g , which is similar to that of the ν process arising from the local motion of water molecules primarily observed in uncrystallized aqueous solutions. 6,7,19−21 Cerveny and co-workers investigated the dynamics of water in a partially crystallized poly(vinylpyrrolidone) (PVP)−water mixture with a PVP concentration of 55 wt % during isothermal crystallization, 11 and three relaxation processes, termed as I, II, and III, were observed in partially crystallized samples. The authors attributed these processes to the dynamics of water instead of the dynamics of ice owing to the properties of these processes.…”

“…Therefore, Cerveny and co-workers concluded that process III in partially crystallized PVP−water mixtures is related to the rotational motion of interfacial water. 11 Recently, our group investigated the dynamics of pure ice and ice in partially crystallized mixtures of gelatin, a wellknown group of biopolymers. [16][17][18]25 As demonstrated by our previous studies, the dynamics of ice are strongly dependent on the solute concentration.…”

“…The dynamics of polymer–water mixtures at subzero temperatures have previously been widely investigated, particularly the dynamics of water remaining in a liquid state. − Recently, the details of polymer dynamics in water mixtures have been unveiled by broadband dielectric spectroscopy (BDS) , and neutron scattering. , BDS is a powerful technique because of its extremely wide time window, which covers molecular dynamics ranging from liquid to glassy states. Numerous studies have been reported for high-polymer-concentration mixtures, in which water cannot be crystallized, by BDS − and also for partially crystallized aqueous solutions by means of BDS. − In this paper, partially crystallized aqueous solutions mean the solutions in which water coexists in both liquid and crystalline states. The crystallization process induces phase separation in the mixture, rendering detailed investigations difficult.…”

Water dynamics in the hydration shells of biological and non-biological polymers

“…However, provided that we identify this relaxation to a local bulklike water process (and therefore with little influence from interactions with the solute), it should not be directly affected by the conformation of ε-PLL but only indirectly due to partial water crystallization at low pH. Although the crystalline regions of water may produce "hard confinements" for the amorphous water and thereby alter this water relaxation to relaxation times typical of water in hard confinements, it should be noted that results for both water solutions 30 and water in MCM41 31 have not indicated any change in the water dynamics due to ice formation. Therefore, another possible explanation to consider is the fact that the state of protonation of carboxyl (COOH) and amine (NH 2 ) groups changes at the different pH values.…”