Surface glass transition behaviors of proton end capped poly(2-vinylpyridine) (P2VP-H) and perfluoroalkyl end capped poly(2-vinylpyridine) (P2VP-C2C8F) thin films were investigated based on temperature-dependent lateral force microscopic (TDLFM) measurement. It is found that the species of chain end groups have significant influence on the surface glass transition temperature of the thin polymer film. For both samples, it is revealed that the surface glass transition temperatures decrease significantly in comparison to the bulk ones, and the magnitude order of reduction in surface Tg for P2VP-C2C8F is larger than that for P2VP-H. The apparent activation energy of surface α-relaxation calculated from the Arrhenius plot is ca. 292 ± 40 and 212 ± 40 kJ/mol for P2VP-H and P2VP-C2C8F, respectively, and is much smaller than the bulk one. The depression of the surface Tg for thin polymer films is explained by the excess free volume induced by the enrichment of chain end groups at the surface.
|ジャーナル||Physics Letters, Section A: General, Atomic and Solid State Physics|
|出版ステータス||出版済み - 4 2 2001|
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