In Figure , the PMF for both surfactants in n-hexadecane becomes slightly positive (endergonic) at distances of 8 Å and 12 Å, which corresponds to the second and third density maxima in Figure . This implies an energy barrier to adsorption due to penetration of the strongly layered final n-hexadecane layer, which may affect the adsorption kinetics. On the other hand, the PMF remains negative at all distance for the surfactants in isooctane, suggesting that there is no energy barrier for adsorption even when the deposit-DCA interactions are mediated by the tail-group of the former.