Local Uniaxial Order in a Grafted Polymer Melt via Deuterium NMR

Dynamics of end-grafted polymer chains on a solid substrate are investigated by deuterium NMR, which is sensitive to the anisotropy of molecular motions. The experiments are performed on a perdeuterated polydimethylsiloxane melt grafted on planar silica slides. The NMR spectra show clearly that chain segments undergo uniaxial reorientations around the normal to the interface. This local order reveals the existence of orientational correlations between chain segments. The corresponding degree of anisotropy is much higher than in other lamellar systems such as block copolymers.