STUDY OF THE SURFACE GLASS-TRANSITION BEHAVIOR OF AMORPHOUS POLYMER FILM BY SCANNING-FORCE MICROSCOPY AND SURFACE SPECTROSCOPY

The surface molecular motion of amorphous polymeric solids has been di rectly measured by lateral force microscopic (LFM), scanning viscoelas ticity microscopic (SVM) and differential X-ray photoelectron spectros copic (D-XPS) measurements. SVM and LFM measurements revealed that the molecular motion on the surface of the monodisperse PS film with Mn l ess than ca. 30 k was fairly active compared with that in the bulk, ma inly due to the surface segregation of chain end groups. The chain end group segregation at the air/PS interface was verified by dynamic sec ondary ion mass spectroscopic depth profiling of the proton and deuter ium ion for end-labelled PS film. These results suggest that surface T -g 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 molecu lar motion of symmetric poly(styrene-block-methyl methacrylate) dibloc k copolymer [P(St-b-MMA)] films. It was confirmed by D-XPS that the su rface molecular motion of the PS component in [P(St-b-MMA)] diblock co polymer films was gradually activated with decreasing depth from the a ir/polymer interface. (C) 1998 Elsevier Science Ltd. All rights reserv ed.