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Surface Enrichment and Evaporation in a Polymer Mixture of Long and Short Chains

Published online by Cambridge University Press:  21 February 2011

Russell J. Composto ,
Richard S. Stein ,
Gian P. Felcher ,
Abdelkader Mansour  and
Alamgir Karim
Russell J. Composto
Affiliation:
Polymer Research Institute, University of Massachusetts, Amherst, MA 01003
Richard S. Stein
Affiliation:
Polymer Research Institute, University of Massachusetts, Amherst, MA 01003
Gian P. Felcher
Affiliation:
Argonne National Laboratory, Argonne, IL 60439
Abdelkader Mansour
Affiliation:
Argonne National Laboratory, Argonne, IL 60439
Alamgir Karim
Affiliation:
Argonne National Laboratory, Argonne, IL 60439
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Abstract

Neutron reflectivity has been used to determine the concentration profile at the vacuum-polymer interface for a two polymer blend. To quantify surface enrichment and evaporation due to differences in chain length, we have measured the reflectivity of a mixture of short deuterated and long protonated polystyrene chains (DPS & PS), with a weight fraction of 0.5. When a mixture of DPS and PS chains of molecular weight 720 and 910k respectively were annealed, a small but measurable increase in asymptotic reflectivity occured, coupled with a decrease of film thickness and scattering length density. This is indicative of surface enrichment and evaporation of the light chains (DPS). Ellipsometry studies confirmed that the short chains evaporated and its rate was established as a function of the temperature. Upon increasing the DPS molecular weight to 9600, the enrichment becomes considerably greater whilst the evaporation becomes negligible.

Type
Research Article
Information
MRS Online Proceedings Library (OPL) , Volume 166: Symposium J – Neutron Scattering for Materials Science , 1989 , 485
Copyright
Copyright © Materials Research Society 1990

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References

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