Hydrogen Bonding and Compartmentalization of Water in Supercooled and Frozen Aqueous Acetone Solutions

Temperature ramp Fourier transform infrared (FTIR) microspectroscopy was utilized to examine hydrogen bonding (HB) in and crystallization of supercooled aqueous acetone solutions. We showed that temperature and concentration-dependent transitions between different water populations, representing distinct HB organization, played very significant roles in ice crystallization and formation of distinct thermodynamic phases in supercooled aqueous solutions. At cryogenic temperatures, mainly three different coexisting thermodynamic phases were identified: a hexagonal ice phase, which exhibited linear planar growth with supercooling; a low water content supercooled solution rich in water monomers and dimers, which froze at lower temperatures as a result of a significant increase in HB networking; and a high water content frozen solution. We show that spectroscopic analysis water in polar solutions at cryogenic temperatures present a unique platform to explore the freezing/melting/vitrification behavior of water.