Structure and Dynamics of Nanoconfined Water between Surfactant Monolayers

Robert M. Ziolek, Franca Fraternali, Ali Dhinojwala, Mesfin Tsige, Christian D. Lorenz*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

6 Citations (Scopus)
207 Downloads (Pure)

Abstract

The properties of nanoconfined water arise in direct response to the properties of the interfaces that confine it. A great deal of research has focused on understanding how and why the physical properties of confined water differ greatly from the bulk. In this work, we have used all-atom molecular dynamics (MD) simulations to provide a detailed description of the structural and dynamical properties of nanoconfined water between two monolayers consisting of an archetypal ionic surfactant, cetrimonium bromide (CTAB, [CH3(CH2)15N(CH3)3]+Br-). Small differences in the area per surfactant of the monolayers impart a clear effect on the intrinsic density, mobility, and ordering of the interfacial water layer confined by the monolayers. We find that as the area per surfactant within a monolayer decreases, the mobility of the interfacial water molecules decreases in response. As the monolayer packing density decreases, we find that each individual CTAB molecule has a greater effect on the ordering of water molecules in its first hydration shell. In a denser monolayer, we observe that the effect of individual CTAB molecules on the ordering of water molecules is hindered by increased competition between headgroups. Therefore, when two monolayers with different areas per surfactant are used to confine a nanoscale water layer, we observe the emergence of noncentrosymmetry.

Original languageEnglish
Pages (from-to)447-455
Number of pages9
JournalLangmuir
Volume36
Issue number1
Early online date12 Dec 2019
DOIs
Publication statusPublished - 14 Jan 2020

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