Surface forces apparatus (SFA) studies on n-octadecyltriethoxysilane self-assembled monolayers on untreated and plasma-treated mica

Prehydrolyzed n-octadecyltriethoxysilane (OTE) molecules were self-assembled as a monolayer on both untreated and argon/water vapor plasma-treated mica. The properties and stability of these monolayers have been qualitatively and quantitatively investigated with a surface forces apparatus (SFA) under various environmental conditions The interaction force between the OTE monolayers immersed in water showed that plasma treatment reduced the range of the steep short-range repulsion and motivated the water vapor studies. The humidity tests revealed a substantial monolayer swelling in the untreated case at 95% RH or higher but there was no swelling in the plasma treated case. Furthermore, adhesive force measurements as a function of variations in environmental conditions such as temperature, relative humidity, contact time, and high stress showed that the plasma treated OTE monolayer appears to be more stable than the untreated monolayer in high humidities. In dry conditions both rnonolayers are molecularly smooth, well ordered and highly compact as well as mechanically robust and tenacious. Finally, the thickness compressibility studies in both dry and humid conditions suggested that the OTE phase state for both the plasma treated and untreated cases is pseudo-crystalline. Further, these studies suggested that the monolayer on both plasma treated and untreated mica does not fully cover the entire surface and likely exists as two very discrete phase states composed of large crystalline polymerized OTE domains and somewhat hydrophilic gaseous regions. The results from several different SFA experiments strongly indicates the OTE-SAM is covalently attached at least partially to the plasma treated mica while the monolayer weakly physisorbs to the untreated mica surface. Accordingly, due to the covalent connection, the OTE-SAM on plasma treated mica is more stable particularly in highly humid or even completely wet environments although it is thought the monolayer does not fully cover the mica surface.

Name thesis:degree_name

Ph.D.

Level thesis:degree_level

doctoral

Discipline thesis:degree_discipline

Graduate College

Grantor dc:publisher

The University of Arizona.

Year dc:date.issued

2001

Author dc:creator

• Kim, Sung-Soo

Advisor dc:contributor.advisor

• Curry, Joan E.

• Chemistry, Physical.
• Physics, Molecular.
• Environmental Sciences.

Statement dc: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.

Language dc:language.iso

en_US

Handle dc:identifier.uri

http://hdl.handle.net/10150/289739

OAI identifier oai:identifier

oai:repository.arizona.edu:10150/289739