Physico-chemical changes at the interface between two polymer surfaces have a significant effect on adhesion and the molecular level processes associated with it. Although rheo-photoacoustic (RPA) Fourier transform infrared (FT-IR) spectroscopy was developed to establish the origin of polymer-polymer interfacial interactions, no correlations were made between the spectroscopic data and the work of adhesion. In this study, we attempt to provide a relationship between the vibrational energy changes in the C-H stretching region in polyethylene, induced by the interfacial stresses resulting from elongations of the polyethylene-polydimethylsiloxane double-layer system, and the work of adhesion. Stresses induced in the interfacial regions allow a correlation between the film thickness and the vibrational energy changes in the symmetric C-H bands.