Octadecyltrimethoxysilane (OTMS) was spread on the water surface of a Langmuir trough. Utilizingthe high-intensity synchrotron X-ray radiation at the Advanced Photon Source at Argonne NationalLaboratory, the kinetics of film growth of OTMS as a function of the subphase pH was studied. In situgrazing incidence X-ray diffraction experiments at the air/water interface revealed that OTMS self-assemblesinto small domains and that the number of these ordered domains increases as OTMS undergoes hydrolysis/condensation reactions. The hexagonal packing of alkyl chains found in the OTMS monolayer is consistentwith the ordering found in bulk OTMS by powder X-ray diffraction.
