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Dynamics of interacting interphases in polymer bilayer thin films

Published online by Cambridge University Press:  17 October 2017

David D. Hsu
Department of Physics & Engineering, Wheaton College, 501 College Avenue, Wheaton, IL 60187, USA
Wenjie Xia
Materials Science and Engineering Division, National Institute of Standards and Technology, 100 Bureau Drive, M/S 8550, Gaithersburg, MD 20899, USA Center for Hierarchical Materials Design, Northwestern University, Evanston, IL 60208, USA Department of Civil & Environmental Engineering, Northwestern University, 2145 Sheridan Road, Evanston, IL 60208, USA
Jake Song
Department of Materials Science & Engineering, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, MA 02139, USA Department of Materials Science & Engineering, Northwestern University, 2145 Sheridan Road, Evanston, IL 60208, USA
Sinan Keten*
Department of Civil & Environmental Engineering, Northwestern University, 2145 Sheridan Road, Evanston, IL 60208, USA Department of Mechanical Engineering, Northwestern University, 2145 Sheridan Road, Evanston, IL 60208-3109, USA
Address all correspondence to Sinan Keten at
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We investigate how the local glass-transition temperature (T g) depends on film thickness in monolayer and bilayer thin films with a polystyrene (PS) upper-layer and a poly(methyl methacrylate) (PMMA) lower-layer using coarse-grained simulations. Interactions between overlapping interphases demonstrate a superposition principle for describing their glass-transition behaviors. For supported bilayer films, the free surface effect on a PS film upper-layer is effectively eliminated due to an enhanced local T g near the PS–PMMA interface, which cancels out depressed T g near the free surface. However, at very low PMMA lower-layer thicknesses, the PMMA-substrate effect can penetrate through the polymer–polymer interface, leading to enhanced T g in the PS upper-layer.

Research Letters
Copyright © Materials Research Society 2017 

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