Volume 60, Number 4, November 2002
|Page(s)||559 - 565|
|Section||Condensed matter: structure, mechanical and thermal properties|
|Published online||01 November 2002|
Dynamics of polymer thin films in supercritical carbon dioxide
Department of Material Science &
Engineering, State University of New York
at Stony Brook - Stony Brook, NY 11794-2275, USA
2 Center for Neutron Research, National Institute of Standards and Technology Gaithersburg, MD 20899, USA
3 Department of Chemistry, State University of New York at Stony Brook Stony Brook, NY 11794-3400, USA
Accepted: 29 August 2002
In situ neutron reflectivity and dynamic secondary ion mass spectrometry measurements were used to investigate the dynamics of polystyrene thin films in supercritical carbon dioxide (sc). The results show that the large degree of anomalous swelling observed is associated with a decrease in glass transition temperature that occurs only within a narrow region of the phase diagram associated with the density fluctuation ridge in sc region. Furthermore, the plasticization effect induced by the density fluctuations was found to enhance the polymer interdiffusion by 2 orders of magnitude as the ridge was approached. Within the ridge the diffusion coefficients scale as M2 and can be approximated by an effective William-Landel-Ferry (WLF) equation.
PACS: 61.25.Hq – Macromolecular and polymer solutions; polymer melts; swelling / 64.70.Pf – Glass transitions / 66.10.Cb – Diffusion and thermal diffusion
© EDP Sciences, 2002
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