Since thin polymeric films are ubiquitous in technological applications such as paints, lubricants, and adhesives, a critical characterization of their thermophysical properties is essential. A central premise in the development of theories for predicting the properties of polymer melts in confined geometries is that chains maintain their unperturbed Gaussian conformation, which they adopt in the bulk, in the direction parallel to the surfaces under all conditions [1,2]. These assumptions, which form the foundations of the important field of polymer thin films, have been questioned on the basis of indirect experimental findings [3,4]. We have utilized the power of small angle neutron scattering, especially the high neutron flux at NCNR, to unequivocally characterize the chain structure and conformation in ultrathin polymer films, and thus have resolved this important fundamental question.
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