Reconsideration of deuterium NMR observations of orientational coupling in polymer networks in light of motional heterogeneity in styrene-d8-styrene block copolymers

It is demonstrated that in entangled melt at temperatures well above T g (T>Tig+60°C) the 2 H NMR line width of a deuterated end block of lengthy M e /10 is roughly one-fifth to one fourth that of a centre block of comparable length. This difference is a manifestation of the greater motional freedom of segments near a free end compared to segments in the interior of an entangled chain