Coexisting lamellar phases in water–oil–surfactant systems induced by the addition of an amphiphilic block copolymer

We report here a pioneering study using quadrupolar splitting NMR to detect new phases and phase compositions in the quasi-ternary microemulsion system water–decane–C10E4/PEP5-PEO5. The striking observation is that at certain compositions the polymer is apparently no longer incorporated into the membranes of the lamellar phase due to space restrictions. The polymer therefore induces a phase separation into two different lamellar phases Lα1 and Lα2 such that it fits into Lα1 while the excess surfactant forms a polymer-free Lα2 phase.

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