W0023

Neutron Reflection for Probing Interfacial Roughness. A. Karim, Polymers Division, National Institute of Standards and Technology, Gaithersburg, MD 20899 and G.P. Felcher*, Material Science Division, Argonne National Laboratory, Argonne, IL 60439

In the last decade neutron reflectivity has emerged as a key tool for the investigation of surfaces and buried interfaces in flat films. Neutron reflectivity covers a dynamical range of q = 0.2 inverse angstroms, where the reflectivity typically drops to values of 10^-7. Correspondingly, the real space resolution of the technique is only slightly better than 1nm. In spite of this spatial limitation, the technique has shown its usefulness in probing density gradients in polymers, since the resolution is on the order of the monomer size. In this endeavor, isotopic (deuterium) labeling of hydrogen in some of the polymeric chains present in different layers has been of paramount importance. Examples will be shown illustrating how polymer blends and solutions partially separate at the air surface or at the inorganic substrate interface, and how well defined is the interface between two incompatible polymer layers. Since the dynamics of polymer melts (in liquid form) is quite slow, the interdiffusion of miscible polymers could be followed in real time, clarifying the difference between diffusion of long-chain polymeric liquid molecules and small molecules of inorganic materials.

*Work at Argonne supported by the U.S. Department of Energy, BES contract #W-31-109-ENG-38