DESCRIBING ORIENTATION TEXTURE IN SMALL ANGLE SCATTERING. John D. Barnes, NIST Polymer Structure and Mechanics Group, NIST, Gaithersburg, MD 20899

This presentation attempts to demonstrate how crystallite orientation distribution functions of the kind used in texture analysis for wide-angle x ray diffraction can be extended to provide tools for simulating small-angle scattering from anisotropic materials.

In WAXD the crystallite orientation distribution causes a single point of the reciprocal lattice to be distributed over the surface of a sphere (pole figure). In many materials SAS arises from microdomains that possess an orientation distribution. The scattering from the contents of these microdomains is, however, finite over extended regions of reciprocal space. This contrasts with the situation in WAXD where the scattering is confined to the discrete points of the reciprocal lattice for the domains. One must also account for the fact that microdomains in SAS are not all identical. This means that the distribution functions must account for variations in such parameters as element size, shape, and degree of perfection as well as orientation. These considerations are illustrated by SAS results from highly anisotropic scatters including block copolymers, semicrystalline polymers, and track etched membranes.