Article ID | Journal | Published Year | Pages | File Type |
---|---|---|---|---|
1584675 | Materials Science and Engineering: A | 2006 | 4 Pages |
Abstract
We have studied glass transition temperature and thermal expansivity of polystyrene thin films supported on silicon substrate using X-ray reflectivity and inelastic neutron scattering techniques. In annealing experiments, we have found that the reported apparent negative expansivity of polymer thin films is caused by unrelaxed structure due to insufficient annealing. Using well-annealed films, we have evaluated glass transition temperature Tg and thermal expansivity as a function of film thickness. The glass transition temperature decreases with film thickness and is constant below about 10Â nm, suggesting the surface glass transition temperature of 355Â K, which is lower than that in bulk. We have also found that the thermal expansivity in the glassy state decreases with film thickness even after annealing. The decrease has been attributed to hardening of harmonic force constant arising from chain confinement in a thin film. This idea has been confirmed in the inelastic neutron scattering measurements.
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Physical Sciences and Engineering
Materials Science
Materials Science (General)
Authors
R. Inoue, T. Kanaya, T. Miyazaki, K. Nishida, I. Tsukushi, K. Shibata,