The entropic component, -T ∆ C S DS -,W ⊕C (z), is due to the combined effect of: (1) the difference between moving the DS -tail cavity from bulk water into the C 12 E 6 monolayer (in ACWI adsorption), and moving the DS - cavity from bulk water into the vacuum (in AWI adsorption), (2) the difference between solvent structuring from significant DS -head group water-desolvation (in ACWI adsorption) and a much smaller degree of head group water-desolvation (in AWI adsorption), and (3) any effects due to changes in the conformational and orientational distributions of DS -at the ACWI compared to those at the AWI, as well as small 55 contributions from the van der Waals interactions between DS - and C 12 E 6 . These effects are depicted as a cartoon in Fig. . As is seen in Fig. , the net effect is a repulsive -T ∆ C S DS -,W ⊕C (z), indicating that the repulsive cavity component overpowers the attractive head group water-desolvation effect.