Some remarks on the chain segment dynamics in confined polymers

Recently, the chain dynamics of molten polymers in confined geometries has been investigated, using NMR. Some of these experiments have been performed on poydimethylsiloxane (PDMS) confined in planar nanolayers involving non-adsorbant solid surfaces. Here the data obtained on various PDMS systems are compared. The common property to these systems is that the local dynamics is anisotropic and the chain segments are undergoing uniaxial fluctuations around the normal $\overrightarrow{\rm n}$ to the layers. Our data clearly show that the sign of the degree of orientational order S (i.e. the direction of the fluctuations around $\overrightarrow{\rm n}$) and the broadening of the order distribution P(S) both result from the relative influence of the impenetrable interfaces and anchoring junctions on the segment behaviour