TY - JOUR
T1 - Structure and Dynamics of Nanoconfined Water between Surfactant Monolayers
AU - Ziolek, Robert M.
AU - Fraternali, Franca
AU - Dhinojwala, Ali
AU - Tsige, Mesfin
AU - Lorenz, Christian D.
PY - 2020/1/14
Y1 - 2020/1/14
N2 - 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.
AB - 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.
UR - http://www.scopus.com/inward/record.url?scp=85077694085&partnerID=8YFLogxK
U2 - 10.1021/acs.langmuir.9b03130
DO - 10.1021/acs.langmuir.9b03130
M3 - Article
C2 - 31826618
AN - SCOPUS:85077694085
SN - 0743-7463
VL - 36
SP - 447
EP - 455
JO - Langmuir
JF - Langmuir
IS - 1
ER -