1. Glass transition dynamics and surface layer mobility in unentangled polystyrene films
- Author
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Yang, Zhaohui, Fujii, Yoshihisa, Lee, Fuk Kay, Lam, Chi-Hang, and Tsui, Ophelia K.C.
- Subjects
Polystyrene -- Thermal properties ,Transition temperature -- Research ,Science and technology - Abstract
Most polymers solidify into a glassy amorphous state, accompanied by a rapid increase in the viscosity when cooled below the glass transition temperature ([T.sub.g]). There is an ongoing debate on whether the [T.sub.g] changes with decreasing polymer film thickness and on the origin of the changes. We measured the viscosity of unentangled, short-chain polystyrene films on silicon at different temperatures and found that the transition temperature for the viscosity decreases with decreasing film thickness, consistent with the changes in the [T.sub.g] of the films observed before. By applying the hydrodynamic equations to the films, the data can be explained by the presence of a highly mobile surface liquid layer, which follows an Arrhenius dynamic and is able to dominate the flow in the thinnest films studied. 10.1126/science.1184394
- Published
- 2010
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