Influence of the alkyl surfactant tail on the adhesion between emulsion drops

Foam or emulsion films stabilized by ionic surfactants can exhibit strong a dhesion in the presence of salts. We study, in this letter, the influence o f the alkyl surfactant tail on the adhesion. We show that the chain length does not play an important role, whereas the presence of alkyl groups bound near the polar head greatly modifies the energy of adhesion. Our results s uggest that the adhesion is mainly driven by the polar heads and the molecu lar structure in their vicinity rather than by van der Waals interactions b etween the alkyl tails.