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Thermal Expansion and Glass Transition Behaviour of Thin Polymer Films with and without a Free Surface Via Neutron Reflectometry

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Abstract

The thermal expansion of thin deuterated polystyrene (dPS) films supported on energetically repulsive, fluorinated polyimide (PI) substrates (PI/dPS bilayer) was measured via neutron reflectometry as a function of initial dPS film thickness. Film thickness was measured before and after capping with a top layer of the same repulsive, high glass transition polyimide that comprised the substrate layer (PI/dPS/PI trilayer) in an attempt to observe any effects of the dPS free surface in the bilayer geometry. Bulk thermal expansion behavior, characterized by a discontinuous change in coefficient of thermal expansion (CTE) at the glass transition (Tg), is observed in films with thickness > 70 rim. For thicknesses between 70 nm and 40 nm a transition is seen from bulk behavior in bilayer films to glassy thermal behavior in the trilayer films persisting up to 20 °C above the bulk Tg. In films with thickness < 40 nm the bulk glassy CTE persists well above the bulk Tg for both bilayer and trilayer films

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Authors and Affiliations

  1. Electronic Applications Group, Polymer Division, NIST, Gaithersburg, MD, USA

    D. J. Pochan, E. K. Lin & Wen-Li Wu

  2. NIST Center for Neutron Research, NIST, Gaithersburg, MD, USA

    S. Satija

  3. Department of Polymer Science, University of Akron, Akron, OH, USA

    S. Z. D. Cheng

Authors
  1. D. J. Pochan
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  2. E. K. Lin
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  3. S. Satija
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  4. S. Z. D. Cheng
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  5. Wen-Li Wu
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Pochan, D.J., Lin, E.K., Satija, S. et al. Thermal Expansion and Glass Transition Behaviour of Thin Polymer Films with and without a Free Surface Via Neutron Reflectometry. MRS Online Proceedings Library 543, 163–168 (1998). https://doi.org/10.1557/PROC-543-163

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  • DOI: https://doi.org/10.1557/PROC-543-163

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