Ellipsometric study of the liquid/pyrex surface: Evidence for orientational order and layering

Abstract

In this paper we use a phase-modulated ellipsometer to study the liquid/Pyrex surface. The Pyrex surface is shown to be well characterized by a hydrated surface with a thickness of ∼ 10 Å. The hydrated Pyrex model explains the ellipsometric data for air, carbon tetrachloride, cyclohexane, and methanol in contact with Pyrex and also gives good agreement with the background ellipticity for the two-phase region of the binary liquid mixture cyclohexane-methanol in the methanol-rich phase where no intruding wetting layer exists. At the aniline/Pyrex surface the ellipsometric results suggest that the aniline electron lone pair on the nitrogen atom and the π bonds on the aromatic carbon ring both form hydrogen bonds with the underlying water layer. This surface-induced orientational order decays to bulk liquid structure over ∼ 7 molecular diameters in qualitative agreement with previous results for layering of liquids against solid surfaces.