Spectroscopic Observation of Fluid Molecular Alignment in a Molecularly-Thin Confined Geometry

For the first time, we present data of molecular alignment of a linear chain (1,3-dicyanopropane) under confinement. Confinement was produced between two mica surfaces within a surface forces apparatus (SFA) and measurements employed confocal Raman spectroscopy. We focused on the CH$_{2}$ symmetric stretch vibrations and CN triple bond stretch vibrations. A polar plot of Raman band intensity as a function of incident light polarization allows us to determine the orientation and order parameter of alignment. It is confirmed that alignment can be achieved in molecularly-thin films. The decrease of alignment as the film thickness increases will be mentioned. Also, the effect of shear on molecular alignment will be discussed.