Heterogeneity of the chain segment dynamics and ordering in lamellar layers of a symmetric triblock copolymer

The segmental ordering within the sublayers of a lamellar polystyrene-polydimethylsiloxanepolystyrene triblock (PS-PDMS-PS) is examined by NMR. The carbon and deuterium NMR line shapes of the PDMS sequence ( soft block) reveal clearly a wide distribution of segmental orientational order S in the lamellae and thus a distribution of constraints probed by the chains. It is observed that this distribution is mainly due to the coexistence of positive and negative S, resulting from a competitive ordering effect induced by the presence of glassy interfaces ( S < 0 in their vicinity) and the chain-end anchoring junctions ( S > 0).