Small-angle scattering of interacting particles.: III.: D2O-C12E5 mixtures and microemulsions with n-octane

Binary and ternary mixtures of C12E5, n-octane, and D2O were examined by neutron scattering experiments. The scattering data are evaluated using the generalized indirect Fourier transformation, GIFT, to determine the particle shape and structure in real space. This recently developed technique allows for the simultaneous determination of the form factor and the structure factor with a minimum of a priori information. All microemulsion data, both on the water-rich side and on the oil-rich side, can be evaluated using the whole range of scattering data to determine the form factor and the structure factor in one procedure. By example of the binary water-surfactant mixture known to contain elongated particles, we were able to show the great advantage in using the GIFT instead of other techniques. Suppression of the interaction effects during the evaluation procedure by eliminating data at low angles leads to incorrect results because elongated particles appear to be globular. The GIFT, however, allows us to distinguish between intra- and interparticle scattering contributions so that the correct elongated shape of the particles is recovered from the scattering data. Therefore, the GIFT can be regarded as the method of choice to determine size, shape, and internal structure of colloidal particles with high accuracy in the size range of 1 to 100 nanometers up to volume fractions of about 0.3. (C) 1999 American Institute of Physics. [S0021-9606(99)50218-3].