A method is proposed to determine the spectral function of the clipped-random-wave (CRW) model directly from scattering data. The spectral function $f\left(k\right)\mathrm{}$ (k is a wave number) gives the distribution of the magnitude of wave vectors of the sinusoidal waves that describes the essential features of the two-phase morphology. The proposed method involves “inverse clipping” of a correlation function to obtain $f\left(k\right)\mathrm{}$ and does not require any a priori assumptions for $f\left(k\right).$ A critical test of the applicability of the inverse-clipping method was carried out by using three-component bicontinuous microemulsions. The method was then used to determine $f\left(k\right)\mathrm{}$ of the bicontinuous structure of a phase-separating polymer blend. $f\left(k\right)\mathrm{}$ for the polymer blend turned out to be a multipeaked function, while $f\left(k\right)\mathrm{}$ for the microemulsions exhibits a single broad maximum representing periodicity of the morphology. These results indicate the presence of the long-range regularity in the morphology of the polymer blend. Three-dimensional (3D) morphology corresponding to the scattering data of the polymer blend was generated using the CRW model together with the multipeaked $f\left(k\right).$ Interface curvatures of the 3D morphology calculated from $f\left(k\right)\mathrm{}$ were measured and compared with those experimentally determined directly from the laser scanning confocal microscopy in the same blend.

• Received 20 October 1999

DOI:https://doi.org/10.1103/PhysRevE.61.6773