Thermal Expansion of Supported Thin Polymer Films: A Direct Comparison of Free Surface vs. Total Confinement
D J. Pochan, Eric K. Lin, Sushil K. Satija, Wen-Li Wu
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 αr, 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.
, Lin, E.
, Satija, S.
and Wu, W.
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 February 26, 2024)