Polymer thin films and surfaces: Possible effects of capillary waves |
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Authors: | S Herminghaus |
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Institution: | (1) Applied Physics Laboratory, University of Ulm, D-89069 Ulm, Germany, DE |
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Abstract: | It is discussed how the proximity of a free surface or mobile interface may affect the strain relaxation behavior in a viscoelastic
material, such as a polymer melt. The eigenmodes of a viscoelastic film are thus derived, and applied in an attempt to explain
the experimentally observed substantial shift of the glass transition temperature of sufficiently thin polymer films with
respect to the bulk. Based on the idea that the polymer freezes due to memory effects in the material, and exploiting results
from mode-coupling theory, the experimental findings of several independent groups can be accounted for quantitatively, with
the elastic modulus at the glass transition temperature as the only fitting parameter. The model is finally applied discussing
the possibility of polymer surface melting. A surface molten layer is predicted to exist, with a thickness diverging as the
inverse of the reduced temperature. A simple model of thin polymer film freezing emerges which accounts for all features observed
experimentally so far.
Received 8 August 2001 |
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Keywords: | PACS 64 70 Pf Glass transitions – 68 47 Mn Polymer surfaces – 83 50 Lh Slip boundary effects (interfacial and free surface flows) |
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