On the reflectivity of polymers: Neutrons and X-rays

Over the last few years reflectivity methods have emerged as key tools for the investigation of polymer surfaces and interfaces. The high spatial resolution of these techniques, of the order of 5 A, has provided a means of probing density gradients in polymers on a submolecular level. This resolution, coupled with selective labeling of all or parts of polymer chains has permitted the examination of polymers at surface and interfaces with unsurpassed detail. Herein, a brief review is given on the basic principles of reflectivity, a discussion of some of the areas where reflectivity has made an impact in polymers and a review of a systematic series of studies on block copolymers which serve as an ideal example to emphasize the strengths of reflectivity and how reflectivity can be used to extract detailed information on a specific problem.