TY - JOUR
T1 - Comparison of morphology and mechanical properties of surfactant aggregates at water-silica and water-graphite interfaces from molecular dynamics simulations
AU - Shah, Kunal
AU - Chiu, Patrick
AU - Sinnott, Susan B.
N1 - Funding Information:
This work was supported by the National Science Foundation funded Particle Engineering Research Center at the University of Florida (Grant number EEC-9402989). Dr. José Fortes and Mr. Mayank Jain are acknowledged for their extreme helpfulness in helping us to parallelize the MD program used in this study and for providing computer time. Fruitful discussions with Dr. Brij Moudgil, Dr. Yakov Rabinovich, Mr. Suresh Yeruva, and Mr. Scott Brown are also gratefully acknowledged. We also acknowledge a gift from VMware Corporation and SUR Grant from IBM. Any opinions, findings and conclusions or recommendations expressed in this material are those of the authors and do not necessarily reflect the views of NSF, IBM, or VMware.
PY - 2006/4/1
Y1 - 2006/4/1
N2 - Cationic surfactants are important for a wide range of applications, including controlled drug delivery systems, emulsifiers, and chemical mechanical polishing. It is therefore important to better understand surfactant structure and properties at the solid-liquid interface. Here, classical molecular dynamics simulations with empirical potentials are used to compare the structures and mechanical properties of cationic surfactant micelles at hydrophobic (graphite) and hydrophilic (silica) surface-water interfaces. In particular, the morphology of monolayers and bilayers of C12TAB (n- dodecyltrimethylammoniumbromide) at these interfaces, and their responses to atomic force microscopy indentation, are examined. The simulations predict that surfactant monolayers and bilayers on silica evolve into a spherical micelle structure, in agreement with theoretical models of surfactant morphology. In contrast, surfactant monolayers on graphite evolve into a hemi-cylindrical structure, in agreement with experimental findings. In the simulated indentation of the micelle/silica system, the spherical micelle breaks apart and forms a surfactant monolayer. The indentation force curve has a maximum value of 2.25 nN. On the other hand, the simulated indentation of the micelle/graphite system causes the hemi-cylindrical micelle structure to break apart and the surfactant tails to wrap around the graphite indenter. The indentation force curve has a maximum value of 13 nN.
AB - Cationic surfactants are important for a wide range of applications, including controlled drug delivery systems, emulsifiers, and chemical mechanical polishing. It is therefore important to better understand surfactant structure and properties at the solid-liquid interface. Here, classical molecular dynamics simulations with empirical potentials are used to compare the structures and mechanical properties of cationic surfactant micelles at hydrophobic (graphite) and hydrophilic (silica) surface-water interfaces. In particular, the morphology of monolayers and bilayers of C12TAB (n- dodecyltrimethylammoniumbromide) at these interfaces, and their responses to atomic force microscopy indentation, are examined. The simulations predict that surfactant monolayers and bilayers on silica evolve into a spherical micelle structure, in agreement with theoretical models of surfactant morphology. In contrast, surfactant monolayers on graphite evolve into a hemi-cylindrical structure, in agreement with experimental findings. In the simulated indentation of the micelle/silica system, the spherical micelle breaks apart and forms a surfactant monolayer. The indentation force curve has a maximum value of 2.25 nN. On the other hand, the simulated indentation of the micelle/graphite system causes the hemi-cylindrical micelle structure to break apart and the surfactant tails to wrap around the graphite indenter. The indentation force curve has a maximum value of 13 nN.
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U2 - 10.1016/j.jcis.2005.08.060
DO - 10.1016/j.jcis.2005.08.060
M3 - Article
C2 - 16183072
AN - SCOPUS:33644599154
SN - 0021-9797
VL - 296
SP - 342
EP - 349
JO - Journal of Colloid And Interface Science
JF - Journal of Colloid And Interface Science
IS - 1
ER -