Measurements of the thickness compressibility of an n-octadecyltriethoxysilane monolayer self-assembled on mica

Sungsoo Kim; Kilwon Cho; Joan E Curry

doi:10.1021/la050689r

Measurements of the thickness compressibility of an n-octadecyltriethoxysilane monolayer self-assembled on mica

Langmuir. 2005 Aug 30;21(18):8290-6. doi: 10.1021/la050689r.

Authors

Sungsoo Kim¹, Kilwon Cho, Joan E Curry

Affiliation

¹ Department of Soil, Water and Environmental Science, The University of Arizona, Tucson, Arizona 85721, USA.

PMID: 16114933
DOI: 10.1021/la050689r

Abstract

The surface forces apparatus technique and the Johnson-Kendall-Roberts theory were used to study the elastic properties of an n-octadecyltriethoxysilane self-assembled monolayer (OTE-SAM) on both untreated and plasma-treated mica. Our aim was to measure the thickness compressibilities of OTE monolayers on untreated and plasma-treated mica and to estimate their surface densities and phase-states from the film compressibility. The compressibility moduli of OTE are (0.96 +/- 0.02) x 10(8) N/m(2) on untreated mica and (1.24 +/- 0.06) x 10(8) N/m(2) on plasma-treated mica. This work suggests that the OTE phase-state is pseudocrystalline. In addition, the results from the compressibility measurements in water vapor suggest that the OTE-SAM on both untreated and plasma-treated mica is not homogeneous but rather contains both crystalline polymerized OTE domains and somewhat hydrophilic gaseous regions.