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

Published online by Cambridge University Press:  10 February 2011

D. J. Pochan ,
E. K. Lin ,
S. Satija ,
S. Z. D. Cheng  and
Wen-Li Wu
D. J. Pochan
Affiliation:
Electronic Applications Group, Polymer Division, NIST, Gaithersburg, MD
E. K. Lin
Affiliation:
Electronic Applications Group, Polymer Division, NIST, Gaithersburg, MD
S. Satija
Affiliation:
NIST Center for Neutron Research, NIST, Gaithersburg, MD
S. Z. D. Cheng
Affiliation:
Department of Polymer Science, University of Akron, Akron, OH
Wen-Li Wu
Affiliation:
Electronic Applications Group, Polymer Division, NIST, Gaithersburg, MD
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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

Type
Research Article
Information
MRS Online Proceedings Library (OPL) , Volume 543: Symposium W – Dynamics in Small Confining Systems IV , 1998 , 163
Copyright
Copyright © Materials Research Society 1999

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