Here we employ free energy decompositions (FEDs) to gain a more detailed understanding of the observed cooperative interfacial adsorption between DS -and the C 12 E 6 monolayer, which we refer to as the synergistic effect. As is typical in FEDs with the thermodynamic integration and free energy perturbation techniques, we utilize so-called "alchemical" intermediate states to extract components of the binding free energy due to specific interactions. In particular, the difference between the free energy profile of DS -and that of the corresponding "hydrophobic limit," DS 0 (i.e. turning off the DS -partial charges) quantifies the electrostatic effects on the binding thermodynamics. Additionally, the difference between the free energy profiles of DS -and the "hydrophilic limit" (here taken to be the charged head group after "turning off" tail-solvent dispersion interactions) quantifies the tail effects. FEDs are combined with consequences of the potential distribution theorem (PDT) in order to extract the solute-solvent energy and entropy of the total free energy, as well as the energetic and entropic components of each term within the decomposition.