Eur. Phys. J. E (2010) 32: 255-264
https://doi.org/10.1140/epje/i2010-10651-x

Regular Article

Monte Carlo phase diagram for diblock copolymer melts

Department of Mathematics, University of Reading, RG6 6AX, Whiteknights, Reading, UK

^* e-mail: t.m.beardsley@reading.ac.uk
^** e-mail: m.w.matsen@reading.ac.uk

Received: 29 April 2010
Accepted: 15 June 2010
Published online: 28 July 2010

Abstract

The phase diagram for diblock copolymer melts is evaluated from lattice-based Monte Carlo simulations using parallel tempering, improving upon earlier simulations that used sequential temperature scans. This new approach locates the order-disorder transition (ODT) far more accurately by the occurrence of a sharp spike in the heat capacity. The present study also performs a more thorough investigation of finite-size effects, which reveals that the gyroid (G) morphology spontaneously forms in place of the perforated-lamellar (PL) phase identified in the earlier study. Nevertheless, there still remains a small region where the PL phase appears to be stable. Interestingly, the lamellar (L) phase next to this region exhibits a small population of transient perforations, which may explain previous scattering experiments suggesting a modulated-lamellar (ML) phase.