Me. Montgomery et Mj. Wirth, SPECTROSCOPIC STUDY OF THE MOLECULAR-BASIS OF WETTING OF A C-18 SURFACE BY LONG-CHAIN N-ALCOHOLS, Analytical chemistry, 66(5), 1994, pp. 680-684
Wetting of a chromatographic surface by long-chain n-alcohols was stud
ied on silica plates derivatized with C-18 at chromatographic densitie
s. Contact angle and surface tension measurements were used to determi
ne the amount of wetting, FT-IR was used to ensure that the adsorbed a
lcohol layer was a submonolayer, and frequency-domain fluorescence spe
ctroscopy was used to study the reorientation behavior of a dilute flu
orescent probe in the C-18 monolayer. The experimental results reveal
that the long-chain alcohols adsorb in a submonolayer, interpenetratin
g with the chains of the C-18 monolayer. The data show that this adsor
ption causes the C-18 chains to tilt toward the surface normal and bec
ome more ordered. In contrast to short-chain alcohols, which wet the i
nterface but do not greatly affect the underlying C-18 monolayer, long
-chain alcohols wet the interface but significantly affect the underly
ing C-18 monolayer.