We report here a pioneering study using quadrupolar splitting NNIR 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 L-alpha(1) and L-alpha(2) such that it fits into L-alpha(1) while the excess surfactant forms a polymer-free L-alpha(2) phase. (c) 2006 Elsevier Inc. All rights reserved.