Chain segment order in polymer thin films on a nonadsorbing surface: A NMR study

The dynamics of polydimethylsiloxane chains confined between air and a solid, wettable, and nonadsorbing surface is investigated using deuterium NMR. Chain segments in such molten films undergo uniaxial reorientations around the normal to the surfaces. The influence of the film thickness proves this dynamic uniaxiality involves rapid segment diffusion between both surfaces which impose a high degree of planar orientation. This segmental ordering is observed over a thickness range which depends on the degree of chain entanglements.