Liquid water is a dynamic polydisperse branched polymer

Naserifar, S. and Goddard, W. A. Liquid water is a dynamic polydisperse branched polymer. Proceedings of the National Academy of Sciences, DOI: https://doi.org/10.1073/pnas.1817383116 (2019)


Water plays a critical role in nearly all chemical, biological, and geological processes. Water and its properties is the subject of numerous experimental and computational techniques. Because of JCAP’s interest in developing new catalysts for using solar energy to convert water into fuels and to convert CO2 into organic materials and fuels, the Caltech team is developing a new force field theory that would match very accurately the full quantum mechanics description of water.

The new theory predicts the properties of water extremely accurately, with Tmelt = 273.3 K (273.15 K) and properties at 298 K: ΔHvap = 10.36 kcal/mol (10.52), density = 0.9965 g/cm3 (0.9965), entropy = 68.4 J/mol/K (69.9), and dielectric constant = 76.1 (78.4), where experimental values are in parentheses.

In the paper published in PNAS, researchers show that upon melting, the number of strong hydrogen bonds (SHBs) drops quickly to two in liquid water. These two SHBs couple into chains containing ∼150 waters resembling a branched polymer. This dynamics-branched polymer paradigm may explain long-standing puzzles of water, such as the critical point at 227 K in supercooled water and the observed angular correlations in water that persist for 20 nm. This paradigm for water could have a significant impact on the properties for proteins, DNA, and other materials in aqueous media.

Contact: wag@caltech.edu

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Reprinted from Naserifar, S. and Goddard, W. A. Liquid water is a dynamic polydisperse branched polymer. Proceedings of the National Academy of Sciences, DOI:  https://doi.org/10.1073/pnas.1817383116  (2019)   Snapshot of water at room temperature showing its polymer nature. The strong hydrogen bonds are represented by black lines. This example has 15 branches with a longest single chain of 39 waters and a total of 216 molecules.

Reprinted from Naserifar, S. and Goddard, W. A. Liquid water is a dynamic polydisperse branched polymer. Proceedings of the National Academy of Sciences, DOI: https://doi.org/10.1073/pnas.1817383116 (2019)

Snapshot of water at room temperature showing its polymer nature. The strong hydrogen bonds are represented by black lines. This example has 15 branches with a longest single chain of 39 waters and a total of 216 molecules.

Topology of the water polymer from variety of angles for the polymer structure.

Video from Naserifar, S. and Goddard, W. A. Liquid water is a dynamic polydisperse branched polymer. Proceedings of the National Academy of Sciences, DOI: https://doi.org/10.1073/pnas.1817383116 (2019).