Molecular simulations of surfactants and silanes: Self-assembly in solutions and on surfaces, and friction between monolayers

Persistent Link:
http://hdl.handle.net/10150/280617
Title:
Molecular simulations of surfactants and silanes: Self-assembly in solutions and on surfaces, and friction between monolayers
Author:
Kapila, Vivek
Issue Date:
2004
Publisher:
The University of Arizona.
Rights:
Copyright © is held by the author. Digital access to this material is made possible by the University Libraries, University of Arizona. Further transmission, reproduction or presentation (such as public display or performance) of protected items is prohibited except with permission of the author.
Abstract:
Recent experimental efforts have focused on the development of water-based chemistries to deposit hydrophobic alkylsilane films on the silica surfaces to address the problem of stiction induced failure in MEMS. A detailed molecular level examination of the structure of these films is limited with the available experimental methods. Therefore, this work undertakes an investigation of the structure and properties of self-assembled alkylsilane monolayer films via Monte Carlo (MC), and molecular dynamics (MD) simulations. The existing literature on the surfactant aggregation is used as a guide for modeling the alkylsilanes molecules. However, the current literature is ambiguous whether to describe interactions between the surfactant head groups as short-range or long-range. This work resolves this discrepancy successfully by performing a series of simulations of various structural and interaction models of surfactants. Simulations show that a realistic surfactant aggregation requires an excluded volume of the head groups, necessitating different interaction models in different structural models of surfactants. Next, MC simulations have been used to investigate the impact of the charged group in cationic alkylsilane on the structure of the deposited film. The structure of the films is characterized with the spatial pair correlations at each molecular layer of the deposited films. The long-range correlations are seen for the films of cationic alkylsilanes. Also, the frictional behavior of the alkylsilane films deposited on silica substrates is examined via molecular dynamics simulations. The friction coefficients of the films are obtained as a function of separation between the films, temperature, and velocity of the substrates. The results of the MD simulations support a thermal activation model of friction.
Type:
text; Dissertation-Reproduction (electronic)
Keywords:
Engineering, Materials Science.
Degree Name:
Ph.D.
Degree Level:
doctoral
Degree Program:
Graduate College; Materials Science and Engineering
Degree Grantor:
University of Arizona
Advisor:
Deymier, Pierre A.

Full metadata record

DC FieldValue Language
dc.language.isoen_USen_US
dc.titleMolecular simulations of surfactants and silanes: Self-assembly in solutions and on surfaces, and friction between monolayersen_US
dc.creatorKapila, Viveken_US
dc.contributor.authorKapila, Viveken_US
dc.date.issued2004en_US
dc.publisherThe University of Arizona.en_US
dc.rightsCopyright © is held by the author. Digital access to this material is made possible by the University Libraries, University of Arizona. Further transmission, reproduction or presentation (such as public display or performance) of protected items is prohibited except with permission of the author.en_US
dc.description.abstractRecent experimental efforts have focused on the development of water-based chemistries to deposit hydrophobic alkylsilane films on the silica surfaces to address the problem of stiction induced failure in MEMS. A detailed molecular level examination of the structure of these films is limited with the available experimental methods. Therefore, this work undertakes an investigation of the structure and properties of self-assembled alkylsilane monolayer films via Monte Carlo (MC), and molecular dynamics (MD) simulations. The existing literature on the surfactant aggregation is used as a guide for modeling the alkylsilanes molecules. However, the current literature is ambiguous whether to describe interactions between the surfactant head groups as short-range or long-range. This work resolves this discrepancy successfully by performing a series of simulations of various structural and interaction models of surfactants. Simulations show that a realistic surfactant aggregation requires an excluded volume of the head groups, necessitating different interaction models in different structural models of surfactants. Next, MC simulations have been used to investigate the impact of the charged group in cationic alkylsilane on the structure of the deposited film. The structure of the films is characterized with the spatial pair correlations at each molecular layer of the deposited films. The long-range correlations are seen for the films of cationic alkylsilanes. Also, the frictional behavior of the alkylsilane films deposited on silica substrates is examined via molecular dynamics simulations. The friction coefficients of the films are obtained as a function of separation between the films, temperature, and velocity of the substrates. The results of the MD simulations support a thermal activation model of friction.en_US
dc.typetexten_US
dc.typeDissertation-Reproduction (electronic)en_US
dc.subjectEngineering, Materials Science.en_US
thesis.degree.namePh.D.en_US
thesis.degree.leveldoctoralen_US
thesis.degree.disciplineGraduate Collegeen_US
thesis.degree.disciplineMaterials Science and Engineeringen_US
thesis.degree.grantorUniversity of Arizonaen_US
dc.contributor.advisorDeymier, Pierre A.en_US
dc.identifier.proquest3145081en_US
dc.identifier.bibrecord.b47212500en_US
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