Nucleation and growth in order-to-order transitions of a block copolymer

¹ Foundation for Research and Technology-Hellas (FORTH), Institute of Electronic Structure and Laser - P.O. Box 1527, 711 10 Heraklion Crete, Greece
² Max-Planck Institut für Polymerforschung - Postfach 3148, D-55021 Mainz, Germany
³ Department of Chemistry, State University of New York at Stony Brook Stony Brook, New York 11794-3400, USA

Received: 29 November 1999
Accepted: 2 February 2000

Abstract

A poly(isoprene-b-ethyleneoxide) diblock undergoes multiple ordered state transitions: from a crystalline lamellar , to a hexagonal (Hex) mesophase, to a bicontinuous cubic phase (Gyroid) before disordering (Dis). We have studied the kinetics of the Hex-to-Gyroid, Hex-to- and -to-Gyroid transitions using synchrotron SAXS and rheology. The Hex-to-Gyroid transformation proceeds via a nucleation and growth mechanism with a small mismatch between the two phases, as anticipated by recent theoretical predictions (M.W. Matsen, Phys. Rev. Lett., 80 (1998) 4470). We provide the first quantitative measure of the activation barrier involved in an order-to-order transition and show the importance of nucleation and growth in these transformations.