J. Phys. II France
Volume 4, Numéro 4, April 1994
Page(s) 689 - 702
DOI: 10.1051/jp2:1994156
J. Phys. II France 4 (1994) 689-702

Edge dislocations in copolymer lamellar films

M. S. Turner1, 2, M. Maaloum3, D. Ausserré3, J-F. Joanny1 and M. Kunz4

1  Institut Charles Sadron, 6 rue Boussingault, 67083 Strasbourg Cedex, Franc
2  Cavendish Laboratory, Madingley Road, Cambridge CB3 0HE, U.K.
3  Université du Maine, URA 807, B.P. 535, 72017 Le Mans Cedex, France
4  Ciba-Geigy A.G., Basel CH4002, Switzerland

(Received 6 August 1993, revised 5 January 1994, accepted 6 January 1994)

Thin films of symmetric diblock copolymers on a flat solid surface form lamellae parallel to the substrate. The uppermost layer of the film may be incomplete and made of domains with a thickness equal to the lamellar period L. We investigate these domains both theoretically and experimentally. The domain edge is associated with a dislocation in the lamellar order which has been observed by transmission electron microscopy. We extend the linear elasticity theory of smectic liquid crystals, to include the effect of the surface tension at the air-polymer interface. We calculate the surface profile above a domain edge and the position (depth) of the dislocation. This profile is studied by atomic force microscopy for polystyrene-polybutymethacrylate films. The comparison between theoretical and experimental profiles allows an estimation of the smectic elastic constants and of the internal surface tension between the two blocks of the copolymer.

© Les Editions de Physique 1994