Above it, the HB becomes weak and less stable, the HDL dominates, and hydrophobicity determines the solution. Below this temperature, where the LDL phase and the HB network develops and grows, with the times and CP,conf change behaviors leading to maxima and minima. For water–glycerol, the HB interaction is dominant for all conditions water–methanol, two different T-regions above and below 265 K are observable, dominated by hydrophobicity and hydrophilicity, respectively. We find that, for the HE, all of the studied quantities behave differently. In contrast, DS is studied in terms of the Adam–Gibbs model by obtaining the configurational entropy (Sconf) and the specific heat contributions (CP,conf). From these times, we took advantage of the NMR property to follow the behaviors of each molecular component (the hydrophilic and hydrophobic groups) separately. We measured the relaxation times (T1 and T2) and the self-diffusion (DS). As the liquid water properties are dominated by polymorphism (two coexisting liquid phases of high and low density) due to hydrogen bond interactions (HB), creating (especially in the supercooled regime) the tetrahedral networking, we focused our interest to the HE of these structures. Therefore, the main purpose of this study is to gain new information about hydrophobicity. Nowadays, compared to hydrophilicity, little is known about hydrophobicity. We focused our interest on the hydrophobic effects (HE), i.e., the competition between hydrophilic and hydrophobic interactions. NMR spectroscopy is used in the temperature range 180–350 K to study the local order and transport properties of pure liquid water (bulk and confined) and its solutions with glycerol and methanol at different molar fractions. In particular, the observed CP,conf maxima and its diverging behaviors clearly reveals the presence of the LLT and with a reasonable approximation the liquid–liquid critical point (LLCP) locus in the phase diagram.
#NIST WEBOOK WATER COEFFICIENT OF THERMAL EXPANSION FULL#
The comparison of the evaluated CP,conf isobars with the experimentally measured water specific heat reveals the full consistency of this analysis. Both these transport functions were then studied according to the Adam–Gibbs model, typical of glass forming liquids, obtaining the water configurational entropy and the corresponding specific heat contribution. As an effect of the hydrogen bond (HB) networking, the isobars of both these transport functions evolve with T by changing by several orders of magnitude, whereas their pressure dependence become more and more pronounced at lower temperatures.
We have considered the self-diffusion coefficient DS and the reorientational correlation time τθ (obtained from spin-lattice T1 relaxation times), measured, respectively, in bulk and emulsion liquid water from the stable to well inside the metastable supercooled region. NMR spectroscopic literature data are used, in a wide temperature-pressure range (180–350 K and 0.1–400 MPa), to study the water polymorphism and the validity of the liquid–liquid transition (LLT) hypothesis. A –hopefully- unbiased discussion is presented for both “mainstream” and unconventional theories and trends and future directions are also outlined. Various explanatory mechanisms for the exclusion zone are reviewed and a new proposal is put forward. New experimental results for the debated phenomena of water bridge and exclusion zone are also presented and discussed. We review some research trends related to water's structure, properties and applications. This review, aiming at a broader/general audience, attempts to review briefly Moreover, water's structure and dynamics are not entirely understood either and new theories have appeared and debated during the 21st century. The origin of these anomalous properties is far from clear, with the strong hydrogen bonds of water being only part of the answer. It has been suggested that making use of water's “anomalous” properties can lead to exciting applications in various disciplines e.g. Water is a fascinating substance with lots of properties not encountered in other compounds.