| Abstract
| - Parabolic focal conics develop at 10−20 wt % surfactant in thetwo-phase lamellar−isotropic regionsof various systems (SDS−hexanol−decane−water, alkylpolyglucosideAPG600−fatty alcohols pentanol,hexanol, decanol, dodecanol, tetradecanol, oleyl alcohol).Extended regular quadratic two-dimensionallattices are formed in microslides (0.05−0.4 mm thickness) when onlya small amount (10−15 wt %) ofthe isotropic phase is present. Five different focal planes can bevisualized with the polarization microscope.The midplane focus gives pictures which look like primitivetwo-dimensional lattices of equally sizedvesicle droplets. The 1:1 mixtures give irregular patternformation. Removal of the isotropic phase bya 20 min centrifugation at 3000g leads to ordinary focalconics. Parabolic focal conics seem to be formedwhen the isotropic phase and the coexisting lamellar phase havecomparable compositions, and this leadsto the assumption that both phases should be in a near-critical state.The formation of parabolic focalconics looks more like a spinodal demixing than a crystallizationprocess with nucleation. The very regularparabolic focal conics are transient states which change to mosaictextures, which look very similar tohexagonal fan textures, whereas polycrystalline parabolic focal conicstransform to ordinary focal conicsafter several days or weeks.
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