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Neutron Reflection Study of Surface Enrichment in an Isotopic Polymer Blend

Published online by Cambridge University Press:  22 February 2011

R.A.L. Jones ,
L.J. Norton ,
E.J. Kramer ,
R.J. Composto ,
R.S. Steint ,
T.P. Russell ,
G.P. Felcher ,
A. Mansour  and
A. Karim
L.J. Norton
Affiliation:
Materials Science and Engineering, Cornell University, Ithaca, NY 14850
E.J. Kramer
Affiliation:
Materials Science and Engineering, Cornell University, Ithaca, NY 14850
R.J. Composto
Affiliation:
Department of Polymer Science and Engineering, University of Massachusetts, Amherst, MA 01003
R.S. Steint
Affiliation:
Department of Polymer Science and Engineering, University of Massachusetts, Amherst, MA 01003
T.P. Russell
Affiliation:
IBM Almaden Research Center, San Jose, CA 95120
G.P. Felcher
Affiliation:
Materials Science Division, Argonne National Laboratory, Argonne, IL 60439—4814
A. Mansour
Affiliation:
Materials Science Division, Argonne National Laboratory, Argonne, IL 60439—4814
A. Karim
Affiliation:
Materials Science Division, Argonne National Laboratory, Argonne, IL 60439—4814
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We have measured neutron reflectivities from the surface of films of deuterated polystyrene (d-PS) and protonated polystyrene (PS) blends before and after annealing, and used the results to determine the concentration versus depth profile of the films. After annealing, the surface is enriched in d-PS, with a surface excess proportional to the bulk concentration of d-PS, in agreement with previous measurements using forward recoil spectrometry[l]. The decay of the enhanced concentration into the bulk occurs over a length approximately equal to the bulk correlation length (∼200 A), in closeagreement with that predicted by current mean-field theoryometry[2]. However, the agreement between the experimental reflectivity curves and the fitted curves is not completely adequate. Figure 1, a plot of k4R against k, demonstrates thi point for a 15% d-PS sample. The dashed line is the best fit assuming the mean field profile. The inset shows the corresponding concentration profile and a trial profile, solidline, which fits the data much better. The small deviation between the theoretical and trial profiles may be due to the assumption of the theory that surface interactions leading to enrichment is short ranged.

Type
Research Article
Information
MRS Online Proceedings Library (OPL) , Volume 171: Symposium O – Polymer Based Molecular Composites , 1989 , 335
Copyright
Copyright © Materials Research Society 1990

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References

REFERENCES

1. Jones, R.A.L., Kramer, E.J., Rafailovich, M.H., Sokolov, J., Schwarz, S.A., Phys. Rev. Let. 62, 280 (1989).Google Scholar
2. Schmidt, I. and Binder, K., J. Physique 46, 1631 (1985).Google Scholar
3. Jones, R.A.L., Norton, L.J., Kramer, E.J., Composto, R.J., Stein, R.S., Russell, T.P., Mansour, A., Karim, A., Felcher, G.P., Rafailovich, M.H., Sokolov, J., Zhao, X., Schwarz, S.A., submitted for puplication.Google Scholar