J. Phys. I France
Volume 6, Numéro 6, June 1996
Page(s) 837 - 857
DOI: 10.1051/jp1:1996245
J. Phys. I France 6 (1996) 837-857

Copolymer Melts in Disordered Media

S. Stepanow1, A.V. Dobrynin2, 3, T.A. Vilgis4 and K. Binder5

1  Martin-Luther-Universität Halle-Wittenberg, Fachbereich Physik, D-06099 Halle/Saale, Germany
2  Groupe de Physico-Chimie Théorique, E.S.P.C.I., 10 Rue Vauquelin, 75231 Paris Cedex 05, France
3  Department of Chemistry, University of North Carolina, Chapel Hill, NC 27599, USA
4  Max-Planck-Institut für Polymerforschung, Postfach 3148, D-55021 Mainz, Germany
5  Institut für Physik, Johannes-Gutenberg Universität Mainz, Staudinger Weg 7, D-55099 Mainz, Germany

(Received 3 July 1995, revised 5 January 1996, accepted 5 March 1996)

We have considered a symmetric AB block copolymer melt in a gel matrix with preferential adsorption of A monomers on the gel. Near the point of the microphase separation transition such a system can be described by the random field Landau-Brazovskii model, where randomness is built into the system during the polymerization of the gel matrix. By using the technique of the 2-nd Legendre transform, the phase diagram of the system is calculated. We found that preferential adsorption of the copolymer on the gel results in three effects: a) it decreases the temperature of the first order phase transition between disordered and ordered phase; b) there exists a region on the phase diagram at some small but finite value of the adsorption energy in which the replica symmetric solution for two replica correlation functions is unstable with respect to replica symmetry breaking; we interpret this state as a glassy state and calculate a spinodal line for this transition; c) we also consider the stability of the lamellar phase and suggest that the long range order is always destroyed by weak randomness.

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