Viscosity and Surface-Promoted Slippage of Thin Polymer Films Supported by a Solid Substrate

Thermally activated flow dynamics of polystyrene films supported by silicon is studied for a wide range of film thickness (h 0) and molecular weights (M w). At low M w, the effective viscosity of the nanometer thin films is smaller than the bulk and decreases with decreasing h 0. This is due to enha...

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Bibliographic Details
Published in:Macromolecules 2015-07, Vol.48 (14), p.5034-5039
Main Authors: Chen, Fei, Peng, Dongdong, Lam, Chi-Hang, Tsui, Ophelia K. C
Format: Article
Language:English
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Summary:Thermally activated flow dynamics of polystyrene films supported by silicon is studied for a wide range of film thickness (h 0) and molecular weights (M w). At low M w, the effective viscosity of the nanometer thin films is smaller than the bulk and decreases with decreasing h 0. This is due to enhancement of the total shear flow by the augmented mobility at the free surface. As M w increases, with h 0 becoming smaller than the polymer radius of gyration (R g), the effective viscosity switches from being substrate-independent to substrate-dependent. We propose that interfacial slippage then dominates and leads to plug flow. The friction coefficient is found to increase with h 0 providing h 0/R g < ∼1, demonstrating a surface-promoted confinement effect.
ISSN:0024-9297
1520-5835
DOI:10.1021/acs.macromol.5b01002