Supercooled Low-Entropy Water Clusters

The properties of low-entropy water clusters and small bulk water domains in a hydrophobic solvent over a wide temperature range (235-333 K), including supercooling temperatures, were investigated. H-1 nuclear magnetic resonance spectroscopy showed singularity temperatures at similar to 300, 250, 235, and 225 K. We proposed a model to understand these singularity temperatures in which the low-entropy water cluster is a locally favored tetrahedral structure (LFTS) and the small bulk water domain contains a mixture of disordered normal-liquid structure (DNLS) and LFTS. The model showed that the LFTS and DNLS populations change with applied temperature. Above similar to 300 K, all local water structures become a DNLS. The population of LFTS increases with cooling and becomes dominant below similar to 250 K. At similar to 225 K, all local water structures converge to LFTS. The phase-transition rate of the low-entropy water clusters and small bulk water domains increases significantly at similar to 235 K. The phase transition of the low-entropy water clusters showed primary ice nucleation. Low-entropy water clusters in a hydrophobic solvent are a unique water morphology and a probe material for water investigations.