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

The dynamics of polydimethylsiloxane chains confined between air and a soli d, wettable, and non-adsorbing 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 thi s dynamic uniaxiality involves rapid segment diffusion between both surface s which impose a high degree of planar orientation. This segmental ordering is observed over a thickness range which depends on the degree of chain en tanglements. PACS numbers: 61.25.Hq. 68.45.Gd, 76.60.-k.