The surface molecular motion of amorphous polymeric solids has been directly measured by lateral force microscopic (LFM), scanning viscoelasticity microscopic (SVM) and differential X-ray photoelectron spectroscopic (D-XPS) measurements. SVM and LFM measurements revealed that the molecular motion on the surface of the monodisperse PS film with Mn less than ca. 30 k was fairly active compared with that in the bulk, mainly due to the surface segregation of chain end groups. The chain end group segregation at the air/PS interface was verified by dynamic secondary ion mass spectroscopic depth profiling of the proton and deuterium ion for end-labelled PS film. These results suggest that surface Tg is depressed because of an increase in free volume near the surface region, induced by the preferential surface localization of chain end groups. D-XPS was utilized for the characterization of surface molecular motion of symmetric poly(styrene-block-methyl methacrylate) diblock copolymer [P(St-b-MMA)] films. It was confirmed by D-XPS that the surface molecular motion of the PS component in [P(St-b-MMA)] diblock copolymer films was gradually activated with decreasing depth from the air/polymer interface.
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