Molecular conformation and nanomechanics of self-assembled alkylsiloxane monolayers

Abstract

We have studied the chain conformation and nanomechanical properties of pure alkylsiloxane monolayers and the mixed films with fluorine-containing species using scanning force microscopy (SFM) and infrared-visible sum-frequency generation spectroscopy (IV-SFG). Our IV-SFG spectra yield information about the chain ordering and surface density of specific species in the pure and mixed monolayers. A film formation process involving preferential adsorption of the fluorinated species from solution was observed. On the basis of the SFM measurements, the stiffness of alkylsiloxane monolayers under load was found to increase with the chain length, changes of chain conformation, and alkyl chain fluorination.