Finite-size effects on surface segregation in polymer blend films above and below the critical point of phase separationH. Grüll1, 2, L. Sung1, A. Karim1, J. F. Douglas1, S. K. Satija1, M. Hayashi3, H. Jinnai3, T. Hashimoto3 and C. C. Han1
1 Material Science and Engineering Laboratory, National Institute of Standards and Technology (NIST) - Gaithersburg, MD 20899-8542, USA
2 Philips Research - 5656 AA Eindhoven, The Netherlands
3 Department of Polymer Chemistry, Graduate School of Engineering Kyoto University - Kyoto 606-8501, Japan
(Received 26 August 2003; accepted in final form 5 January 2004)
We investigate the influence of temperature and confinement on surface segregation in thin films of deuterated polybutadiene and polyisoprene near the critical point for phase separation. Neutron reflectivity measurements show that polyisoprene enriches at the air and silicon interfaces in both the 1- and 2-phase regions. A transition between in-plane and surface-directed (layered) phase separation is observed with increasing film thickness. Weak critical adsorption effects cause the blend composition profile to be rounded in comparison with profiles normally measured in small liquid mixtures.
61.12.Ha - Neutron reflectometry.
68.08.Bc - Wetting.
05.70.Fh - Phase transitions: general studies.
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