Thermal Expansion of Supported Thin Polymer Films: A Direct Comparison of Free Surface vs. Total Confinement

Published

April 1, 2001

Author(s)

D J. Pochan, Eric K. Lin, Sushil K. Satija, Wen-Li Wu

Abstract

Neutron Reflectivity measurements on thin, deuterated polystyrene films reveal a strong dependence of the polymer melt coefficient of thermal expansion (CTE) on both the thickness of the film and the specific pair of substrate and superstrate confinement boundaries present. A direct comparison is made between the behavior of films on low energy, fluorinated polyimide (fPI) substrates with a free surface (bilayer geometry) and the behavior of the exact same films after capping with a superstrate layer of fPI (trilayer geometry). A significant drop in α_r, the CTE above the bulk glass transition, is observed in bilayers at thickness d x substrates and in light of the low-energy nature of the fluorinated confinement layers, suggests subtle entropic mechanisms induced by the fPI confinement layers that strongly alter the material properties from their bulk values.

Citation

Macromolecules

Volume

34

Issue

No. 9

Pub Type

Journals

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Keywords

confined geometries, neuron reflectivity, polymer thin films, thermal expansion

Citation

Pochan, D. , Lin, E. , Satija, S. and Wu, W. (2001), Thermal Expansion of Supported Thin Polymer Films: A Direct Comparison of Free Surface vs. Total Confinement, Macromolecules, [online], https://tsapps.nist.gov/publication/get_pdf.cfm?pub_id=851654 (Accessed April 16, 2024)