The surface molecular motion of polymeric solids was investigated on the basis of scanning force microscopic and temperature-dependent X-ray photoelectron spectroscopic measurements. The surface of the monodisperse polystyrene films was in a glass-rubber transition state even at 293 K in the case of number-average molecular weight less than ca. 30k. The surface glass transition temperature, Tgs for the symmetric poly(styrene-block-methyl methacrylate) diblock copolymer films were much lower than those for the bulk samples. A remarkable depression of Tg at the air-polymer interface was explained by the surface localization of chain end groups.
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