Dynamics of Water in Partially Crystallized Solutions of Glass Forming Materials and Polymers: Implications on the Behavior of Bulk Water
Kapitel i bok, 2020
There is no simpler compound than water. It is the most copious substance on Earth and the most important constituent for life, as we know. There is also a continuous scientific interest due to its exceptional and infrequent properties, such as a density maximum at 4 ℃ (at atmospheric pressure), a high specific heat capacity, and a low viscosity under high pressure, among other macroscopic properties. The origin of the unusual properties of water is evidenced at lower temperatures in the no man’s land temperature region (235–150 K), where bulk water cannot remain in an amorphous state. Instead, in this region, bulk water crystallizes in a complex phase diagram with more than 16 crystalline phases. Therefore, most of the work done so far on supercooled water focuses on the investigation of the dynamics when crystallization is suppressed using different types of confinements, such as nano-cavities or by mixing water with other solutes (polymers, proteins, or DNA). On the contrary, in this chapter, we will use broadband dielectric spectroscopy to analyze the dynamics of aqueous solutions and confined water when it is partially crystallized, i.e., when liquid water and ice coexist. With this technique, it is possible to obtain information about the molecular relaxations in both amorphous and crystalline phases. We have analyzed the results of this semi-crystalline water and compared them with the response of supercooled water in fully amorphous solutions. Finally, we discuss the implications of these results on the behavior of bulk water.