Thickness dependence of free‐standing thin films |
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| Authors: | Gérald Guérin Robert E Prud'homme |
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| Institution: | 1. Centre de recherche en sciences et ingénierie des macromolécules, Département de chimie, Université Laval, Sainte‐Foy, Québec G1K 7P4, Canada;2. Centre de recherche en sciences et ingénierie des macromolécules, Département de chimie, Université Laval, Sainte‐Foy, Québec G1K 7P4, CanadaDepartment of Chemistry, University of Montréal, C.P. 6128, Succursale Centre‐ville, Montréal, Québec H3C 3J7, Canada |
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| Abstract: | Below a critical thickness, of about 60 nm, the glass transition temperature of polystyrene (PS) films decreases with film thickness, as demonstrated using free‐standing films. A geometrical model is developed here describing this phenomenon in the case of ideal (Gaussian) chains. This model, which can be considered as an application of the free volume model, assumes that the decrease of the glass transition temperature from thick to ultrathin films is due to the modification of the interpenetration between neighboring chains. The theoretical curve deduced from the model is in excellent agreement with the PS experimental results, without using any adjustable parameters. From these results, it can be concluded that new chain motions, usually buried in bulk samples, are expressed by the presence of the surface. © 2006 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 45: 10–17, 2007 |
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| Keywords: | glass transition polystyrene thin films |
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