Issue |
Europhys. Lett.
Volume 40, Number 6, December II 1997
|
|
---|---|---|
Page(s) | 643 - 648 | |
Section | Condensed matter: structure, thermal and mechanical properties | |
DOI | https://doi.org/10.1209/epl/i1997-00517-6 | |
Published online | 01 September 2002 |
Thickness-induced morphology changes in lamellar diblock copolymer ultrathin films
The James Franck Institute and Department of Physics,
The University of Chicago,
Chicago, Illinois 60637, USA
Received:
14
April
1997
Accepted:
5
November
1997
We have investigated the morphology of lamellar polystyrene-polymethylmetha cry late diblock copolymers in the ultrathin-film limit, spin-cast and annealed on silicon nitride substrates. Our experiments show evidence for a morphology change from lamellar domains parallel to the substrate to perpendicular domains that appears to be unique to a thickness of one lamellar repeat spacing and low annealing temperatures. We find that in these ultrathin films phase separation occurs well before thickness quantization, suggesting effective confinement as a possible mechanism. A model for the free energy of this system is developed which takes into account termination ("capping") of the perpendicular lamellae inside the film and at its top surface.
PACS: 61.41.+e – Polymers, elastomers, and plastics / 68.55.Jk – Structure and morphology; thickness / 68.10.Cr – Surface energy (surface tension, interface tension, angle of contact, etc.)
© EDP Sciences, 1997
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