Issue
EPL
Volume 77, Number 4, February 2007
Article Number 48002
Number of page(s) 5
Section Interdisciplinary Physics and Related Areas of Science and Technology
DOI http://dx.doi.org/10.1209/0295-5075/77/48002
Published online 25 January 2007
EPL, 77 (2007) 48002
DOI: 10.1209/0295-5075/77/48002

Case-II diffusion and solvent-polymer films drying: A meso-scale model

M. Souche and D. Long

Laboratoire de Physique des Solides, UMR 8502 CNRS/Université de Paris sud - Bât. 510, 91405 Orsay Cédex, France

long@lps.u-psud.fr

received 28 August 2006; accepted in final form 12 December 2006; published February 2007
published online 25 January 2007

Abstract
We propose a model for calculating a constitutive relation for the dynamics of solvent-polymer systems close to the glass transition. We do it by considering a layer of thickness $\xi $ of a few nanometers which is submitted to an arbitrary time varying solvent activity a(t). We show then how these constitutive relations allow to explain case-II diffusion in glassy polymers and provide a physical interpretation for the parameters of the Thomas-Windle model. Regarding the process of film drying, we show that films up to $1\,\mu {\rm m}$ thick can be almost completely dried in an accessible experimental time, even at temperatures well below the polymer glass transition temperature. When drying a thicker film, we show that a glassy crust may appear on the free surface, as has been shown experimentally.

PACS
83.80.Rs - Polymer solutions.
66.20.+d - Viscosity of liquids; diffusive momentum transport.
61.41.+e - Polymers, elastomers, and plastics.

© Europhysics Letters Association 2007