SURFACE GRAININESS AND A NEW MODEL OF NONIONIC MICELLE OF OCTAOXYETHYLENE ALKYL ETHER

Surface graininess and micelle size of n-dodecyl (octaoxyethylene glycol) monoether C12H25(OCH2CH2)8OH in an isotropic liquid phase (L1 phase) and a hexagonal mesophase (H1 phase) of an aqueous colloid were investigated through light scattering and small angle X-ray scattering (SAXS). The micelle is almost spherical and the micelle radius remains about 28 - 30 angstrom over a wide concentration range from the critical micelle concentration (ca. 4·10-5 g/ml) to 0.3 g/ml. The aggregation number is 70 - 80 and depends slightly on temperature. The specific inner surface Os of the spherical micelle is obtained from the tail portion (large angle region) in the SAXS curve. The value of Os of the micelle in the L1 phase is ca. 0.2 angstrom-1 and this value is approximately twice as large as that of a smooth sphere. A new micelle model is also proposed.