We developed an energy model derived from the first principle for multilayer configurations to enhance our understanding of the interfacial property between two polymers under shear deformation. We carried out specific experiments satisfying the boundary and loading conditions of the model to obtain the energy dissipation factor (0), which characterized and quantified the interfacial property. Two polymer pairs, the miscible system polystyrene (PS)/high-impact polystyrene (HIPS) and the immiscible system polycarbonate (PC)/liquid-crystal polymer (LCP), were investigated. As expected, beta was zero for PS/HIPS, reflecting the strong interaction at the PS/HIPS interface. For PC/LCP, the value of beta could be significant, and its behavior was complex; it reflected the thermal sensitivity and thermal history effect of the PC/LCP interface. A positive value of beta also indicated the possibility of slip at the interface and provided an explanation for the negative deviation from the rule of mixture. This complex behavior of the interface was attributed to the changes in the phases and microstructure of LCPs and, therefore, the LCP/PC interface as thermal cycling was carried out in the melting/nematic range of LCPs.