Stability of C₁₂E_<i>j</i> Bilayers Probed with Adhesive Droplets

The stability of model surfactant bilayers from the poly­(ethylene glycol) mono-<i>n</i>-dodecyl ether (C₁₂E_<i>j</i>) family was probed. The surfactant bilayers were formed by the adhesion of emulsion droplets. We generated C₁₂E_<i>j</i> bilayers by forming water-in-oil (w/o) emulsions with saline water droplets, covered by the surfactant, in a silicone and octane oil mixture. Using microfluidics, we studied the stability of those bilayers. C₁₂E₁ allowed only short-lived bilayers whereas C₁₂E₂ bilayers were stable over a wide range of oil mixtures. At high C₁₂E₂ concentration, a two-phase region was displayed in the phase diagram: bilayers formed by the adhesion of two water droplets and Janus-like particles consisting of adhering aqueous and amphiphilic droplets. C₁₂E₈ and C₁₂E₂₅ did not mediate bilayer formation and caused phase inversion leading to o/w emulsion. With intermediate C₁₂E₄ and C₁₂E₅ surfactants, both w/o and o/w emulsions were unstable. We provided the titration of the C₁₂E₂ bilayer with C₁₂E₄ and C₁₂E₅ to study and predict their stability behavior