LAMELLAR AND L(3) PHASES IN THE SIMPLE H2O-C(8)E(5)-1-OCTANOL SYSTEM - EVIDENCE OF SYNERGISM

The ternary system water-pentaethylene glycol mono-n-octyl ether-1-oct anol (H2O-C(8)E(5)-C(8)E(0)) has been examined as a function of temper ature. We found that dilute L(alpha) and L(beta) phases are induced by addition of C(8)E(0) to the simple binary system H2O-C(8)E(5), which does not show these phases in the absence of C(8)E(0). In the pseudo-b inary-phase diagram H2O-C(8)E(5)/C(8)E(0), one, accordingly, encounter s phases that are usually only found in longer-chain surfactant system s. The combination of two short-chain molecules C(8)E(5) + C(8)E(0) ap parently results in a strong synergistic effect. We describe the tempe rature-dependent evolution of the complex phase behavior with schemati c diagrams, which permit us to rationalize how the L(alpha) and L(beta ) phases in the isothermal ternary phase diagrams are connected to a m ultitude of two- and three-phase regions.