Eur. Phys. J. E 8, 237-243 (2002)
DOI: 10.1140/epje/i2001-10056-0
Polymer thin films and surfaces: Possible effects of capillary waves
S. HerminghausApplied Physics Laboratory, University of Ulm, D-89069 Ulm, Germany stephan.herminghaus@physik.uni-ulm.de
(Received 8 August 2001)
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.
64.70.Pf - Glass transitions.
68.47.Mn - Polymer surfaces.
83.50.Lh - Slip boundary effects (interfacial and free surface flows).
© EDP Sciences, Società Italiana di Fisica, Springer-Verlag 2002
