Molten hydrate clathrates as a new class of macromolecular fluids.*

Despite water being the most prominent liquid and a common reaction media of biological processes, the effect of hydrophobic solutes on its properties is not completely understood. For instance, apolar chains of tetrabutyl ammonium salts promote the formation of clathrate hydrates at low temperatures or high pressures.
Here we demonstrate the formation of a supramolecular liquid in ≈1.4-2.2m aqueous solutions of tetrabutyl ammonium bromide. Temperature and composition dependent compressibility, FTIR, thermal conductivity and heat capacity suggest that most of water molecules are locally ordered in a liquid clathrate-like structure. This completely rearranges the tetrahedral H-bond network characteristic of bulk water and affects dramatically to its thermodynamic and transport properties. Our results suggest a new way to design macromolecular solvents with different properties than its constituents.