LOCAL UNIAXIAL ORDER IN LAMELLAR STRUCTUR E OF A DIBLOCK COPOLYMER - A DEUTERIUM NMR-STUDY

Chain segment dynamics in the lamellar mesophase of a polystyrene-poly butadiene diblock copolymer is investigated with deuterium NMR (H-2-NM R). Only polybutadiene chains are deuterated and experiments are achie ved with a macroscopically oriented sample- The approach consists in s tudying how nuclear interactions are time-averaged by molecular motion s. The observed H-2-NMR spectra demonstrate that the segmental dynamic s is uniaxial around the direction normal to the lamellar layers. This local uniaxial order suggests that the polybutadiene chains are sligh tly elongated.