Langmuir study of octadecyltrimethoxysilane behavior at the air-water interface

S. Vidon, R. M. Leblanc

Research output: Contribution to journalArticlepeer-review

24 Scopus citations


The behavior of octadecyltrimethoxysilane (C18TMS) at the air-water interface for different subphases pH has been studied through surface pressure-area and surface potential-area isotherms combined with Brewster angle microscopy. C18TMS monomolecular behavior has been assigned to the one observed at pH around 8.0. Hydrolysis or hydrolysis followed by condensation occurs when pH is lowered below 5.0. Hydrolysis followed by condensation is also observed when the pH is raised above 10.5. The type of catalysis predominantly influences the product of the reaction. Condensation is performed at low pH under two constraints: steric hindrance between the C18 tail chains and electrostatic repulsion between polar groups, resulting in a very low or nil polymerization degree of the condensation products around the isoelectric point (pH 3.8). Higher concentration of chloride ions gradually inhibits the second constraint, resulting in the formation of a linear polymer. Only steric hindrance has been observed under basic catalysis, producing a monodimensional polymer similar to the one obtained at low pH.

Original languageEnglish (US)
Pages (from-to)1279-1286
Number of pages8
JournalJournal of Physical Chemistry B
Issue number7
StatePublished - Feb 12 1998

ASJC Scopus subject areas

  • Physical and Theoretical Chemistry
  • Surfaces, Coatings and Films
  • Materials Chemistry


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