SMALL-ANGLE X-RAY-SCATTERING FROM AQUEOUS-SOLUTIONS OF TETRA(OXYETHYLENE)-N-OCTYL ETHER

Aqueous solutions of the nonionic surfactant C(8)E(4) With different m ass fractions of the amphiphile have been studied by small-angle X-ray scattering (SAXS) with dependence on temperature. The demixing temper atures of the samples were determined by viscosity and ultrasonic spee d measurements. The temperature dependence of measures shows discontin uities at demixing of the sample. Below the demixing temperature the v iscosity measurements indicate increasing size of the solute particles . The SAXS curves can be well described throughout the whole temperatu re and composition range with the model of a inhomogeneous sphere with a core radius of about 1 nm. This value is in good agreement with the theoretical length of an all-trans-octyl chain. The combination of th ese results with the viscosity data supports the model of aggregating spherical micelles.