Structure and Dynamics of Trimethylacetonitrile at the Silica/Vapor, Silica/Liquid, and Liquid/Vapor Interfaces

Abstract

Optical spectroscopy has been used to probe the interfacial organization and dynamics of trimethylacetonitrile (TMACN). Molecular orientation at the silica/liquid, silica/vapor and liquid/vapor interfaces of TMACN has been studied using vibrational sum-frequency generation (VSFG) spectroscopy. These studies reveal that TMACN exhibits appreciable organization at each of these interfaces, despite the bulky nature of its tert-butyl group. VSFG spectra measured from the silica/liquid interface suggest that TMACN does not form the sort of well-organized bilayer that has been observed previously for acetonitrile and propionitrile. Optical Kerr effect studies of TMACN confined in porous silica glasses demonstrate that this liquid forms a dynamically inhibited surface layer that is roughly one molecule thick, which is consistent with the organizational model suggested by the VSFG data.