Modified Porod's law estimate of the transition- layer thickness between two phases: test of triangular smoothing function

An analytical method to estimate the thickness of the interface between two phases from small-angle scattering (SAS) data has been developed using Porod's law modi®ed by a triangular smoothing function. The convolution with a `top-hat' function describing a sharp density pro®le results in a semi-sigmoidal density pro®le. This analytical method allows an interfacial layer thickness to be estimated from the negative slope of a Porod plot. The interfacial layer thickness (T) obtained from this model is related to similar models, namely a linear (E) and a sigmoidal density pro®le ( ) model, as follows: T = 2E = 2(6) , where is the standard deviation of the Gaussian function and does not represent the boundary thickness itself. The interfacial layer thickness obtained from any convolution method is a model-dependent parameter.