A series of alkyl phosphates with alkyl chain len
gths ran
gin
g from C
10 to C
18 have been synthesized. Self-assembledmonolayers (SAMs) of these molecules were prepared on titanium oxide surfaces by immersion of the substrates inalkyl phosphate solutions of 0.5 mM concentration in
n-heptane/isopropanol. The SAMs were characterized by meansof dynamic water contact an
gle (dCA) measurements, variable-an
gle spectroscopic ellipsometry (VASE), X-rayphotoelectron spectroscopy (XPS), and polarization-modulated infrared reflection-absorption spectroscopy (PM-IRRAS). A hi
gher de
gree of order and packin
g density within the monolayers was found for alkyl phosphates withalkyl chain len
gths exceedin
g 15 carbon atoms. This is reflected in a lower dCA hysteresis, as well as a film thicknessmeasured by VASE and XPS close to the expected values for SAMs with an avera
ge alkyl chain tilt an
gle of 30
ges/entities/de
g.
gif">to the surface normal. Additionally a shift of the symmetric and antisymmetric C-H stretchin
g modes in the PM-IRRAS spectra to lower wave numbers was observed. These findin
gs imply a hi
gher two-dimensional crystallinityof the films derived from alkyl phosphates with a lon
ger alkyl chain len
gth.
