X-Ray Scattering Methods for the Study of Polymer Interfaces

A variety of characterization methods based on X-ray scattering may be used to sensitively probe the structure of polymer surfaces and interfaces. Among these are small angle scattering in transmission, specular reflectivity, grazing incidence off-specular scattering, and grazing incidence diffraction. X-ray measurements provide information on electron density differences across interfaces, total interfacial area and volume fraction of a dispersed phase, microroughness of sharp interfaces, interface width, parameters of near-interface electron density profiles, and in-plane ordering in thin films and near surfaces. This review focuses on experimental aspects of the methods as analytical techniques, considering the relative merits of different approaches, and reviewing some recent measurements not yet reviewed elsewhere. Particular attention is given to the rapidly growing fields of specular reflectivity and off-specular scattering. After discussing general theoretical concepts applicable to all the techniques and general instrumentation requirements, each method is considered in turn. For each, the basic theory and methods of analysis are presented, followed by a description of specific instrumentation needs and notes on sample preparation. In the cases of off-specular scattering and grazing incidence diffraction some examples of recent applications are reviewed. A few remarks on prospects for further development of the various techniques are offered as well.