Directly Probing Molecular Ordering at the Buried Polymer/Metal Interface

Abstract

We developed a methodology to directly probe molecular ordering at the buried polymer/metal interface. Using sum frequency generation (SFG) vibrational spectroscopy, we observed ordering of ester methyl groups at the buried poly(methyl acrylate) (PMA)/silver (Ag) interface. In order to directly probe the PMA/Ag interface, we collected SFG signal from a thin PMA film sandwiched between a fused silica substrate and a silver surface. It was found that the observed SFG signal intensity does not depend on the PMA film thickness. According to the calculated Fresnel coefficients of the fused silica/PMA and PMA/Ag interfaces with PMA films of different thicknesses, it was shown that SFG signals are solely contributed by the PMA/Ag interface. Further studies indicated that the ester methyl groups at the PMA/Ag interface tilt away from the Ag surface.